Thesis (PhD)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Pentoxifylline enhances the toxicity of radiation and has emerged as an effective modulator of the radiation response of tumour cells. The molecular mechanisms involved in the enhancement of radiotoxicity by pentoxifylline have not yet been elucidated. Cell cycle blocks, DNA repair and programmed cell death (apoptosis) are all pert of the cellular response to DNA damage and as such must be considered as targets of the drug. In this study, the influence of pentoxifylline on radiosensitisation, G2 block abrogation, DNA repair inhibition and the induction of apoptosis have been investigated in 8e11 and MeWo melanoma and 4197 and 4451 squamous cell carcinoma (SCC) cell lines. The influence of pentoxifylline on radiation-induced apoptosis in Jurkat J5 T-lymphocytic leukemia cells has also been assessed. Hela cervical carcinoma cells were used to investigate the molecular events involved in the abrogation of the G2 block by pentoxifylline. It is shown that pentoxifylline preferentially sensitises the TP53 mutant MeWo and 4451 cell lines and enhances radiotoxicity by factors of up to 14.5. In the MeWo melanoma, but not in the 4451 SCC cell line, radiosensitisation is accompanied by inhibition of DNA repair. No significant enhancement of radiation-induced apoptosis was observed in MeWo melanoma and 4451 SCC cells. However, Jurkat J5 cells showed an increase in apoptosis after irradiation in the presence of the drug. In irradiated Hela cervical carcinoma cells, pentoxifylline affects the expression of the two components of the mitosis promoting factor (MPF), namely cyclin 81 and p34cdC2, and rapidly restores cyclin 81/p34cdC2 ratios to control levels. Analysis of cyclin 81 expression in whole cells and isolated nuclei furthermore reveals an influence of the drug on the subcellular translocation of the MPF. It is concluded that G2 block abrogation is not the only mechanism involved in the radiosensitisation of tumour cells by pentoxifylline, but that DNA repair inhibition plays a role in certain cell types. Although pentoxifylline induces apoptosis in Jurkat J5 thymocytes, radiation-induced apoptosis plays no role in the radiosensitisation of the two TP53 mutant melanoma and sec cell lines. Abrogation of the G2 block by pentoxifylline, which sensitises tumour cells to a second irradiation or chemotherapeutic challenge, involves a modulation of the levels of cyclin 81 and p34cdC2, and the subcellular location of the MPF. These results are of utmost importance for the clinical potential of pentoxifylline as a dose modifier in cancer therapy. / AFRIKAANSE OPSOMMING: Pentoxifylline verhoog die toksisiteit van bestraling en het dus na vore getree as 'n effektiewe modulator van die sellulêre stralingsrespons in kankerselle. Die molekulêre meganismes betrokke by die verhoging van stralingstoksisiteit deur pentoxifylline is egter nog nie duidelik nie. Blokkering van die selsiklus, die herstel van ONS skade en geprogrammeerde seldood (apoptose) vorm almal deel van die sellulêre respons ná bestraling en word as sulks beskou as potensiële teikens van die middel. In hierdie studie is die invloed van pentoxifylline op stralings-sensitiwiteit, G2 blok verwydering, die vertraging van ONS herstel en die indusering van apoptose ondersoek in die Be11 en MeWo melanoom en 4197 en 4451 plaveisel-sel karsinoom sellyne. Die invloed van pentoxifylline op stralings-geïnduseerde apoptose in Jurkat J5 T-limfosiete is ook bestudeer. Hela servikale karsinoom selle is gebruik om die molekulêre gebeurtenisse rondom die verwydering van die G2 blok deur pentoxifylline te ondersoek. Dit word aangetoon dat pentoxifylline by voorkeur die radiosensitiwiteit van die TP53 mutante MeWo en 4451 sellyne verhoog, en stralingstoksisiteits verhogingsfaktore van tot 14.5 genereer. Hierdie effek gaan gepaard met die vertraging van ONS herstel in die MeWo melanoom, maar nie in die 4451 plaveisel-sel karsinoom sellyn nie. Die meting van apoptose toon geen noemenswaardige verhoging van stralings-geïnduseerde apoptose in MeWo melanoom óf in 4451 plaveisel-sel karsinoom selle nie. Jurkat J5 T-limfosiete toon egter wel 'n verhoging in apoptose wanneer bestraling in die teenwoordigheid van pentoxifylline gedoen word. In Hela servikale karsinoom selle affekteer pentoxifylline die uitdrukking van die twee komponente van die mitose promoverings faktor (MPF), naamlik siklien B1 en p34CdC2 , en restoreer die siklien 81/p34cdC2 verhoudings vinnig na normale vlakke. Ontleding van die siklien 81 uitdrukking in heel selle en in geïsoleerde selkerne toon verder dat die middelook die sub-sellulêre ligging van die MPF affekteer. Die gevolgtrekking word gemaak dat G2 blok verwydering nie die enigste meganisme is waardeur pentoxifylline radiosensitiwiteit verhoog nie, maar dat die vertraging van ONS herstel in sommige seltipes 'n rol speel. Alhoewel pentoxifylline apoptose verhoog in T-limfosiete, speel dit nie 'n rol in die verhoogde radiotoksisiteit wat waargeneem is in die TP53 mutante melanoom en plaveisel-sel karsinoom sellyne nie. Verwydering van die G2 blok deur pentoxifylline, wat selle meer sensitief kan maak vir 'n tweede stralings- of chemoterapie aanslag, behels die modulasie van siklien 81 en p34cdc2 vlakke en die sub-sellulêre ligging van die MPF. Hierdie resultate is van uiterste belang vir die kliniese aanwending van pentoxifylline as 'n dosis-modifiseerder in kankerterapie.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The "classic" prostate cell lines, DU145, PC-3 and LNCaP, have served as a valuable cell biological model for research into prostate cancer. However, their relevance may be limited because they derive from metastatic, and not from primary normal and tumour epithelium. The cell lines (1532T, 1535T, 1542T, 1542N and BPH-l) have been derived from primary benign and malignant human tumour prostate epithelium and may be more representative. Using these cell lines I have examined the role of basic cell damage responses (repair, checkpoint activation, apoptosis and associated signalling proteins, and the influence of androgen status) in cell inactivation, and its relevance to treatment. Numerous studies have suggested that loss of p53 function leads to resistance to chemotherapeutic agents and irradiation. It is shown here that the p53-inactive cell lines are, in fact, the most sensitive to chemotherapeutic agents such as etoposide, vinblastine and estramustine, whilst the p53 wild-type cell line, LNCaP, is the most radiosensitive. Notwithstanding the effects of p53 degradation by the HPV -16 E6 viral protein, the results on chemosensitivity raises the possibility that different chemotherapeutic agents may have different p53-dependent effects in different tumour cells. Androgen deprivation is demonstrated to sensitise prostate cancer cells to chemotherapeutic agents and it is shown that the hormone independent cell lines are the most chemosensitive. The LNCaP cell line displayed an increased resistance to apoptosis induced by etoposide and gamma irradiation, suggesting that androgens are capable of protection against both these DNA damaging agents. The major factors determining radiosensitivity in human tumour cell lines are known to be DNA double-strand break (dsb) induction and repair. In the prostate cell lines I find that cellular radiosensitivity correlates with the number of DNA double-strand breaks measured within 2 hours of irradiation, and that the more radioresistant cell lines show better repair competence. Conclusions as to the influence of androgen dependence on radiosensitivity and repair are not possible at this stage since only the LNCaP cell line was androgen sensitive. The fact that the 2 hour repair period can separate radiosensitive from radioresistant cells in 2 groups of human tumour cell lines highlights the role of non-homologous end-joining repair. This has implications for therapy, and is consistent with the clinical observation that prostate tumours can be successfully controlled by low dose rate-brachytherapy. To evaluate the role of apoptosis, cells were exposed to TD50 concentrations of chemotherapeutic drugs, and 60Co y-irradiation. Apoptosis was found to be low, overall, and ranged from 0.1% - 12.1%,3.0% - 6.0% and 0.1% - 8.5% for etoposide, estramustine and vinblastine, respectively. The percentage of cells undergoing druginduced apoptosis was, on average, higher in the tumour cell lines than in the normal cell lines. Gamma irradiation-induced apoptosis levels ranged from 1.3% - 7%. The LNCaP cell line yielded the lowest percentage of apoptotic cells after exposure. The l532T cell line yielded the highest percentage of apoptotic cells after exposure. Apoptotic propensity did not rank the cell lines according to their radiosensitivity. Immunoblotting demonstrated that the apoptosis-associated proteins, bax and bcl-2, are expressed at a basal level in all the cell lines tested, but no increase was detected after exposure to TD50 doses of etoposide, vinblastine and estramustine. The ratio of bax and bcl-2 also was not altered by DNA damage. No evidence was found that a correlation may exist between reproductive cell death and the expression of genes which control apoptosis. My results show that apoptosis is not a major mechanism of drug- or radiation-induced cell death in prostate cell lines. In conclusion, loss of p53 function and loss of androgen dependence was not found to be correlated with resistance of tumours to chemotherapeutic drugs. Cellular radiosensitivity was found to be correlated with the number of DNA double-strand breaks remaining after 2 hours of repair. The more radioresistant cell lines showed better repair competence. Apoptosis and genes affecting apoptosis, such as p53 and members of the bcl-2 family, do not seem to contribute significantly to the sensitivity of prostate cancer cells to anticancer drugs and irradiation. / AFRIKAANSE OPSOMMING: Die klassieke prostaat sellyne, DU145, PC-3 en LNCaP, het 'n waardevolle bydrae gemaak in die sel biologiese model in prostaat kanker. Die toepaslikheid daarvan mag egter beperk wees, aangesien hierdie sellyne afkomstig is van metastatiese, en nie van primêr normale en tumor epiteel nie. Die sellyne 1532T, 1535T, 1542T, 1542N en BPH-I is afkomstig van primêre benigne en maligne menslike prostaat tumor epiteel en mag moontlik meer verteenwoordigend wees. Deur van hierdie sellyne gebruik te maak, is die rolondersoek van die reaksie op basiese selskade (d.w.s. herstel, beheerpunt aktivering, apoptose en verwante sein proteïene, en die invloed van androgeen status) tydens die proses van sel inaktivering, asook die toepaslikheid ten opsigte van behandeling. Volgens verskeie studies lei die verlies aan p53 funksie tot weerstandigheid teen chemoterapeutiese middels en bestraling. Die resultate van hierdie studie toon dat die p53-onaktiewe sellyne egter die sensitiefste is vir chemoterapeutiese middels, soos etoposied, vinblastien en estramustien, terwyl die p53 natuurlike-tipe sellyn, LNCaP, die meeste radiosensitief is. Ten spyte van die invloed van p53 afbraak deur die HPV -16 E6 virale proteïen, dui die resultate van chemosensitiwiteit op die moontlikheid dat verskillende chemoterapeutiese middels verskillende p53-afhanklike effekte op verskillende tumorselle mag hê. Dit is bewys dat onttrekking van androgeen prostaat kankerselle sensitiseer teen chemoterapeutiese middels en dat hormoon-onafhanklike sellyne die hoogste chemosensitiwiteit vertoon. Die LNCaP sellyn vertoon 'n verhoogde weerstandigheid teen apoptose wat deur etoposied en y-bestraling geïnduseer is, wat 'n aanduiding is dat androgene beskerming kan bied teen beide hierdie DNA beskadigingsfaktore. Die belangrikste faktore wat die radiosensitiwiteit in menslike tumorselle bepaal, IS bekend dat dit die dubbelbande van DNA verbreek en herstel. Hierdie studie het aangetoon dat in prostaat sellyne die sellulêre radiosensitiwiteit korreleer met die aantal DNA dubbelband verbrekings binne 2 uur na bestraling, en dat die meer radioweerstandige sellyne beter herstelvermoë vertoon. Gevolgtrekkings oor die invloed van androgeen se afhanklikheid van radiosensitiwiteit en herstel kan egter nie op hierdie stadium gemaak word nie, aangesien slegs die LNCaP sellyn androgeenafhanklik was. Die feit dat die 2 uur herstelperiode 'n skeiding kan maak tussen radiosensitiewe en radioweerstandige selle in twee groepe menslike tumor sellyne, onderstreep die rol van herstel van nie-homoloë endverbindings. Dit hou implikasies in vir terapie, en stem ooreen met die kliniese waarnemings dat prostaat tumore suksesvol gekontroleer kan word deur lae intensiteit dosis bragiterapie. Ten einde die rol van apoptose te ondersoek, is selle blootgestel aan TD50 konsentrasies chemoterapeutiese middels, asook 60Co y-bestraling. Apoptose was oor die algemeen laag, en het gestrek van 0.1% tot 12.1%,3.0% tot 6.0% en 0.1% tot 8.5% vir etoposied, estramustien en vinblastien onderskeidelik. Die persentasie selle wat middel geïnduseerde apoptose ondergaan het, was gemiddeld hoër in tumor sellyne as in normale sellyne. Die waardes van apoptose geïnduseer deur y-bestraling het gewissel van 1.3% tot 7.0%. Die LNCaP sellyn het die laagste persentasie apoptotiese selle na bestraling gelewer, terwyl die 1532 r sellyn die hoogste persentasie gelewer het. Die volgorde van die radiosensitiwiteit van die sellyne was nie waarneembaar in hulle geneigdheid tot apoptose nie. Immunoblots het aangetoon dat die apoptose-geassosieerde proteïene, bax en bcl-2, uitgeskei word teen 'n basisvlak in al die sellyne wat getoets is, maar dat geen verhoogde uitskeiding waarneembaar was na blootstelling aan TD50 dosisse etoposied, vinblastien en estramustien nie. Die verhouding van bax en bcl-2 is ook nie beïnvloed deur DNA beskadiging nie. Dit blyk daarom dus onwaarskynlik dat daar 'n korrelasie bestaan tussen reproduktiewe seldood en die uitskeiding van gene wat apoptose beheer. Die resultate dui daarop dat apoptose me 'n belangrike meganisme vir middel- of bestralingsgeïnduseerde seldood in prostaat sellyne is nie.

Thesis (MMed)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Background: HIV is the defining pandemic of our era, with an estimated 5.9 million people infected in South Africa according to World Health Organization (WHO) estimates for 2011. The expression and treatment of non-AIDS defining cancers has become an important consideration in this cohort, as antiretroviral therapy (ART) has prolonged survival in a subgroup previously at risk of early mortality. Study Design: A retrospective cohort study of all women seen at the Combined Breast Cancer Clinic at Tygerberg Hospital between January 2010 and December 2011, stratified into three subgroups based on HIV status. Methods: Of the 816 patients screened, 586 met inclusion criteria; of which 31 (5.3%) patients were HIV positive, 420 (71.7%) HIV negative, and 135 (23%) had an unknown HIV status. The disease phenotype was described in each subgroup, as well as toxicities associated with standard chemotherapy regimens, with an emphasis on completion rates of systemic cytotoxic treatment. The insult of cytotoxic therapy to the CD4 count was described for this cohort. Results: Women with HIV had a statistically significant (p<0.001) younger age at presentation of breast cancer with a median age of 42 years (range 39 – 45 years) in comparison with the HIV-negative cohort with a median age of 54 years (range 53 – 55 years) . No difference was detected in disease phenotype when stage at presentation (p=0.7874), histological subtype (p=0.3375), grade of differentiation (p=0.8297), nodal involvement (p=0.0998) or hormone-receptor positivity (p=0.6285) was considered. Completion rates for systemic chemotherapy were excellent (>90%) regardless of HIV-status and no statistically significant toxicity was observed. The median CD4 count at diagnosis was 477 cells/μL (range 234 – 807 cells/μL), with a nadir value of 333 cells/μL (range 62 – 713 cells/μL), representing a decrease of 30.2% during treatment. One case of suspected treatment-related mortality was recorded. Conclusion: This retrospective study confirmed that women infected with HIV had a younger age at breast cancer diagnosis when compared to women with a negative HIV-status. No difference in disease phenotype could be demonstrated for women with HIV, denoting the coexistence of two common chronic diseases. Chemotherapy was tolerated well, but caused a median decline in CD4-count of 30% during treatment. / AFRIKAANSE OPSOMMING: Agtergrond: Infeksie met die Menslike Immuungebrek-Virus (MIV) is die pandemie van ons era, met ‘n geraamde 5.9 miljoen mense geïnfekteerd in Suid-Afrika volgens die Wêreld Gesondheids-Organisasie (WGO) in 2011. Kankers wat nie met MIV geassosieer word nie, het n belangrike oorweging in hierdie populasie-groep geword as gevolg van die gebruik van anti-retrovirale terapie wat die lewensverwagting van mense met MIV verleng. Navorsingsontwerp: ‘n Retrospektiewe kohort studie van alle vroue wat tydens die tydperk Januarie 2010 en Desember 2011 by die Gekombineerde Borskanker Kliniek te Tygerberg Hospitaal behandel was, verdeel in 3 groepe volgens hul retrovirale status. Metodes: ‘n Totaal van 819 vroue was oorweeg vir insluiting in die studie, waarvan 586 aan die insluitingskriteria voldoen het. Daar was 31 vroue met MIV (5.3%), 420 vroue het MIVnegatief getoets (71.7%), en 135 (23%) vroue waarvan die MIV-status onbekend was. Die fenotipe van borskanker was beskryf vir elke sub-groep, sowel as die toksiteite wat geassosieer word met die gebruik van standaard chemoterapie-skedules, insluitend die effek van chemoterapie op die CD4-telling. Bevindinge: Vroue met MIV het op ‘n statisties noemenswaardige (p<0.001) jonger ouderdom gepresenteer met borskanker (gemiddelde ouderdom 42 jaar, reikwydte 39 – 45 jaar) in vergelyking met vroue wat MIV-negatief was (gemiddelde ouderdom 54 jaar, reikwydte 53 – 55 jaar). Geen verskil was waargeneem in die fenotipe van borskanker in vroue met MIV vir die stadium by diagnose (p = 0.7874), histologiese tipe (p=0.3375), graad van differensiasie (p = 0.8297), nodale betrekking (p = 0.0998) of hormoon-reseptor status (p=0.6285) nie. Voltooing van sistemiese chemoterapie is bereik in meer as negentig persent van gevalle onafhanklik van MIV-status. ‘n Gemiddelde CD4-telling van 477 selle/μL (reikwydte 234 – 807 selle/ μL) met diagnose het ‘n gemiddelde afname van 30.2% tydens behandeling getoon na ‘n gemiddelde waarde van 333 selle/ μL (reikwydte 62 – 713 selle/ μL). Gevolgtrekkings: Hierdie retrospektiewe studie het bevind dat vroue met MIV op ‘n jonger ouderdom met borskanker presenteer as vroue wat MIV-negatief is. Geen noemenswaardige verskil was waargeneem in die fenotipe van borskanker in vroue met MIV nie, en dui daarop dat borskanker en MIV twee algemene, maar onafhanklike entiteite is. Chemoterapie was goed getolereer met ‘n gemiddelde afname in die CD4-telling van 30.2% tydens chemoterapie.

Image guidance has rapidly become central to current radiotherapy practice. A uniform framework is developed for evaluating image quality across all imaging modalities by modelling the ‘universal phantom’: breaking any phantom down into its constituent fundamental test objects and applying appropriate analysis techniques to these through the construction of an automated analysis tree. This is implemented practically through the new software package ‘IQWorks’ and is applicable to both radiotherapy and diagnostic imaging. For electronic portal imaging (EPI), excellent agreement was observed with two commercial solutions: the QC-3V phantom and PIPS Pro software (Standard Imaging) and EPID QC phantom and epidSoft software (PTW). However, PIPS Pro’s noise correction strategy appears unnecessary for all but the highest frequency modulation transfer function (MTF) point and its contrast to noise ratio (CNR) calculation is not as described. Serious flaws identified in epid- Soft included erroneous file handling leading to incorrect MTF and signal to noise ratio (SNR) results, and a sensitivity to phantom alignment resulting in overestimation of MTF points by up to 150% for alignment errors of only ±1 pixel. The ‘QEPI1’ is introduced as a new EPI performance phantom. Being a simple lead square with a central square hole it is inexpensive and straightforward to manufacture yet enables calculation of a wide range of performance metrics at multiple locations across the field of view. Measured MTF curves agree with those of traditional bar pattern phantoms to within the limits of experimental uncertainty. An intercomparison of the Varian aS1000 and aS500-II detectors demonstrated an improvement in MTF for the aS1000 of 50–100% over the clinically relevant range 0.4–1 cycles/mm, yet with a corresponding reduction in CNR by a factor of p 2. Both detectors therefore offer advantages for different clinical applications. Characterisation of cone-beam CT (CBCT) facilities on two Varian On-Board Imaging (OBI) units revealed that only two out of six clinical modes had been calibrated by default, leading to errors of the order of 400 HU for some modes and materials – well outside the ±40 HU tolerance. Following calibration, all curves agreed sufficiently for dose calculation accuracy within 2%. CNR and MTF experiments demonstrated that a boost in MTF f50 of 20–30% is achievable by using a 5122 rather than a 3842 matrix, but with a reduction in CNR of the order of 30%. The MTF f50 of the single-pulse half-resolution radiographic mode of the Varian PaxScan 4030CB detector was measured in the plane of the detector as 1.0±0.1 cycles/mm using both a traditional tungsten edge and the new QEPI1 phantom. For digitally reconstructed radiographs (DRRs), a reduction in CT slice thickness resulted in an expected improvement in MTF in the patient scanning direction but a deterioration in the orthogonal direction, with the optimum slice thickness being 1–2 mm. Two general purposes display devices were calibrated against the DICOM Greyscale Standard Display Function (GSDF) to within the ±20% limit for Class 2 review devices. By providing an approach to image quality evaluation that is uniform across all radiotherapy imaging modalities this work enables consistent end-to-end optimisation of this fundamental part of the radiotherapy process, thereby supporting enhanced use of image-guidance at all relevant stages of radiotherapy and better supporting the clinical decisions based on it.

No description available.

<p>A tenet of modern radiotherapy (RT) is to identify the treatment target accurately, following which the high-dose treatment volume may be expanded into the surrounding tissues in order to create the clinical and planning target volumes. Respiratory motion can induce errors in target volume delineation and dose delivery in radiation therapy for thoracic and abdominal cancers. Historically, radiotherapy treatment planning in the thoracic and abdominal regions has used 2D or 3D images acquired under uncoached free-breathing conditions, irrespective of whether the target tumor is moving or not. Once the gross target volume has been delineated, standard margins are commonly added in order to account for motion. However, the generic margins do not usually take the target motion trajectory into consideration. That may lead to under- or over-estimate motion with subsequent risk of missing the target during treatment or irradiating excessive normal tissue. That introduces systematic errors into treatment planning and delivery. In clinical practice, four-dimensional (4D) imaging has been popular in For RT motion management. It provides temporal information about tumor and organ at risk motion, and it permits patient-specific treatment planning. The most common contemporary imaging technique for identifying tumor motion is 4D computed tomography (4D-CT). However, CT has poor soft tissue contrast and it induce ionizing radiation hazard. In the last decade, 4D magnetic resonance imaging (4D-MRI) has become an emerging tool to image respiratory motion, especially in the abdomen, because of the superior soft-tissue contrast. Recently, several 4D-MRI techniques have been proposed, including prospective and retrospective approaches. Nevertheless, 4D-MRI techniques are faced with several challenges: 1) suboptimal and inconsistent tumor contrast with large inter-patient variation; 2) relatively low temporal-spatial resolution; 3) it lacks a reliable respiratory surrogate. In this research work, novel 4D-MRI techniques applying MRI weightings that was not used in existing 4D-MRI techniques, including T2/T1-weighted, T2-weighted and Diffusion-weighted MRI were investigated. A result-driven phase retrospective sorting method was proposed, and it was applied to image space as well as k-space of MR imaging. Novel image-based respiratory surrogates were developed, improved and evaluated.</p> / Dissertation

<p>Quality assurance (QA) is a critical component of radiation oncology medical physics for both effective treatment and patient safety, particularly as innovations in technology allow movement toward advanced treatment techniques that require increasingly higher accuracy in delivery. Comprehensive 3D dosimetry with PRESAGE® 3D dosimeters read out via optical CT has the potential to detect errors that would be missed by current systems of measurement, and thereby improve the rigor of current QA techniques through providing high-resolution, full 3D verification for a wide range of clinical applications. The broad objective of this dissertation research is to advance and strengthen the standards of QA for radiation therapy, both by driving the development and optimization of PRESAGE® 3D dosimeters for specific clinical and research applications and by applying the technique of high resolution 3D dosimetry toward addressing clinical needs in the current practice of radiation therapy. The specific applications that this dissertation focuses on address several topical concerns: (1) increasing the quality, consistency, and rigor of radiation therapy delivery through comprehensive 3D verification in remote credentialing evaluations, (2) investigating a reusable 3D dosimeter that could potentially facilitate wider implementation of 3D dosimetry through improving cost-effectiveness, and (3) validating deformable image registration (DIR) algorithms prior to clinical implementation in dose deformation and accumulation calculations.</p><p>3D Remote Dosimetry: The feasibility of remote high-resolution 3D dosimetry with the PRESAGE®/Optical-CT system was investigated using two nominally identical optical-CT scanners for 3D dosimetry were constructed and placed at the base (Duke University) and remote (IROC Houston) institutions. Two formulations of PRESAGE® (SS1, SS2) were investigated with four unirradiated PRESAGE® dosimeters imaged at the base institution, then shipped to the remote institution for planning and irradiation. After each dosimeter was irradiated with the same treatment plan and subsequently read out by optical CT at the remote institution, the dosimeters were shipped back to the base institution for remote dosimetry readout 3 days post-irradiation. Measured on-site and remote relative 3D dose distributions were registered to the Pinnacle dose calculation, which served as the reference distribution for 3D gamma calculations with passing criteria of 5%/2mm, 3%/3mm, and 3%/2mm with a 10% dose threshold. Gamma passing rates, dose profiles, and dose maps were used to assess and compare the performance of both PRESAGE® formulations for remote dosimetry. Both PRESAGE® formulations under study maintained high linearity of dose response (R2>0.996) over 14 days with response slope consistency within 4.9% (SS1) and 6.6% (SS2). Better agreements between the Pinnacle plan and dosimeter readout were observed in PRESAGE® formulation SS2, which had higher passing rates and consistency between immediate and remote results at all metrics. This formulation also demonstrated a relative dose distribution that remained stable over time. These results provide a foundation for future investigations using remote dosimetry to study the accuracy of advanced radiation treatments.</p><p>A Reusable 3D Dosimeter: New Presage-RU formulations made using a lower durometer polyurethane matrix (Shore hardness 30-50A) exhibit a response that optically clears following irradiation and opens up the potential for reirradiation and dosimeter reusability. This would have the practical benefit of improving cost-effectiveness and thereby facilitating the wider implementation of comprehensive, high resolution 3D dosimetry. Three formulations (RU-3050-1.7, RU-3050-1.5, and RU-50-1.5) were assessed with multiple irradiations of both small volume samples and larger volume dosimeters, then characterized and evaluated for dose response sensitivity, optical clearing, dose-rate independence, dosimetric accuracy, and the effects of reirradiation on dose measurement. The primary shortcoming of these dosimeters was the discovery of age-dependent gradients in dose response sensitivity, which varied dose response by as much as 30% and prevented accurate measurement. This is unprecedented in the standard formulations and presumably caused by diffusion of a desensitizing agent into the lower durometer polyurethane. The effect of prior irradiation on the dosimeters would also be a concern as it was seen that the relative amount of dose delivered to any given region of the dosimeter will affect subsequent sensitivity in that area, which would in effect create spatially-dependent variable dose sensitivities throughout the dosimeter based on the distributions of prior irradiations. While a successful reusable dosimeter may not have been realized from this work, these studies nonetheless contributed useful information that will affect future development, including in the area of deformable dosimetry, and provide a framework for future reusable dosimeter testing.</p><p>Validating Deformable Image Registration Algorithms: Deformable image registration (DIR) algorithms are used for multi-fraction dose accumulation and treatment response assessment for adaptive radiation therapy, but the accuracy of these methods must be investigated prior to clinical implementation. 12 novel deformable PRESAGE® 3D dosimeter formulations were introduced and characterized for potential use in validating DIR algorithms by providing accurate, ground-truth deformed dose measurement for comparison to DIR-predicted deformed dose distributions. Two commercial clinical DIR software algorithms were evaluated for dose deformation accuracy by comparison against a measured deformed dosimeter dose distribution. This measured distribution was obtained by irradiating a dosimeter under lateral compression, then releasing it from compression so that it could return to its original geometry. The dose distribution within the dosimeter deformed along with the dosimeter volume as it regained to its original shape, thus providing a measurable ground truth deformed dose distribution. Results showed that intensity-based DIR algorithms produce high levels of error and physically unrealistic deformations when deforming a homogeneous structure; this is expected as lack of internal structure is challenging for intensity-based DIR algorithms to deform accurately as they rely on matching fairly closely spaced heterogeneous intensity features. A biomechanical, intensity-independent DIR algorithm demonstrated substantially closer agreement to the measured deformed dose distribution with 3D gamma passing rates (3%/3mm) in the range of 90-91%. These results underscore the necessity and importance of validating DIR algorithms for specific clinical scenarios prior to clinical implementation.</p> / Dissertation

Low and middle-income countries (LMICs) around the world are experiencing a global cancer crisis. For treatable disease, cancer specific mortality in LMICs is much higher than in high-income countries. Botswana is a middle-income country in Sub-Saharan Africa that had its population decimated by the AIDS epidemic. In the aftermath and due to the successful implementation of an anti-retroviral program, patients are living longer and are developing cancer. Cervical cancer is one of the leading causes of death in women around the world, but it is curable. Patients in Botswana live far from treatment centers and therefore often present with locally advanced disease that can be cured with a combination of chemotherapy, external beam radiation therapy and brachytherapy. The goal of this present study is to describe the challenges and implementation of brachytherapy in the country of Botswana in 2012 and to report its uses within the cervical cancer population between 2012 and 2014. The government of Botswana recognized that there was a need for in country brachytherapy to help reduce the cervical cancer burden. A public-private partnership was negotiated through the government of Botswana in order to bring brachytherapy into the country. In March 2011, a Nucletron HDR-Brachytherapy unit that uses Ir-192 was installed at Gaborone Private Hospital. Longitudinal support from international partners provided instruction in insertion, dosimetry, physics and management of complications. The initial burden of patients presented with severe cervical fibrosis and vaginal stenosis due to late presentation of disease. This resulted in numerous complications in the first treatments, which included failed insertions, perforations and bleeding. Following training and support from international partners, complications have been reduced. There are about 45 insertions performed each month, with an average of 3 insertions per patient. Introduction of HDR Brachytherapy to Botswana has led to decreased treatment time, reduced complications, increased patient compliance and projected improved survival. Implementation of brachytherapy was facilitated by a public-private partnership and onsite mentorship by expert clinicians. Further research is needed to evaluate impact on patient quality of life and survival, and whether this experience can be replicated for other tumor sites.

M.Tech. / The aim of this study was to determine the effects of the application of therapeutic reflexology as a complementary medicine, in women with cervical cancer who were receiving radiation therapy with curative intent. Therapeutic reflexology is a therapy that involves stimulating specific reflexes in the hands, feet, body and ears by applying pressure to these reflexes with the thumbs and fingers, using specific techniques. All the body’s organs, glands and other parts of the body are reflected in the feet, body, hands and ears can be stimulated by working over the skin surface with the thumbs and fingers for a specific effect. These specific reflexes have been mapped in miniature on the feet, hands, body and ears (Graham, 1998: 5). Therapeutic reflexology promotes homeostasis within the body, by stimulating reflexes pertaining to organs and glands, and achieving normalisation of organs and glands in the receiver of the treatment. The therapy is non - invasive and non - pharmacological, and has no contra-indications (Graham, 1998: 8). Therapeutic reflexology is often used as a complementary or alternative medicine, yet very little information is available on its effects, which requires further research (Milligan, 2002: 489-96). The number of cancer patients using reflexology as a complementary therapy to allopathic medicine is rapidly rising (Apostolides, 1998: 71-95) It is because of this rise in the number of patients seeking complementary therapy that it is of vital importance that more accurate, results-orientated information is made available to both the patient and the medical practitioner. These findings will allow the patient and medical practitioner to make an informed decision regarding the choices available to complement allopathic medicine, to enhance wellbeing, and achieve better results for the allopathic protocol. A sample group of forty-four women were chosen by simple random selection. Twenty three were treated with therapeutic reflexology, and twenty one were given the placebo treatment for six weeks, while undergoing radiation therapy. The patients chosen for the sample group had stage IIIb as well as stage IIb cervical cancer, and were receiving radiation treatment. The result of the study has been determined by evaluating a questionnaire answered by each patient, after each treatment. The control group who received placebo treatment answered the same questionnaire, formulated in accordance with the Likert Scale, for means of comparison.

The central hypothesis supporting the present work is that the effectiveness of radiation therapy for cancer is often limited due to defects in key apoptosis regulators, such as Bcl-2 family members, that contribute to cancer ability to evade apoptosis. One way to bypass this resistance to radiotherapy is to target cell death pathways, aiming to sensitize tumours to radiation and enhance the therapeutic ratio in cancer. To test this central hypothesis, we took a dual approach: one targeted apoptosis and the other targeted autophagy. / First, we focused on the apoptotic signaling. The Bcl-2 family comprises antiapoptotic members, such as Bcl-2, Mcl-1, and Bcl-XL, and proapoptotic members, such as Bax, Bak, and Bid. The Bcl-2 family controls the integrity of the outer mitochondrial membrane and is critical in determining the susceptibility of cells to apoptosis induced by the intrinsic pathway. The balance between cell survival and cell death is modulated by the ratios and interactions of antiapoptotic and proapoptotic Bcl-2 family proteins. Overexpression of Bcl-2 or Bcl-XL is observed in several cancers, including lung, colorectal, prostate, and breast cancers, and has been shown to confer resistance to various anticancer agents, including radiotherapy. In cancer cells, alterations in the amounts of these antiapoptotic Bcl-2 proteins promote cell survival, among others by contributing to their evasion from treatment-induced apoptosis. We made the observation that lung cancer cells have different radiosensitivity. On the basis of their relative response to radiotherapy, we stratified lung cancer cells into two groups (higher or lower sensitivity), and selected a representative cell line of each group for more in-depth study: A549 (resistant) and HCC2429 (sensitive). We found that the expression levels of Bcl-XL expression, which is antiapoptotic, was dramatically higher in A549, whereas almost not detected in HCC2429. We then hypothesized that AT-101, a pan-Bcl-2 inhibitor, had the potential to radiosensitize lung cancer by restoring radiation-induced apoptosis. When administered alone, AT-101 resulted in increased apoptosis in a concentration-dependent manner in both groups, with enhanced activity in HCC2429 even at lower concentration. Furthermore, AT-101 promoted radiosensitivity of A549 and HCC2429 cells (p < 0.005). A549 cells required increased AT-101 dose to achieve the same level of cytotoxicity than HCC2429 cells. These investigations suggest that the Bcl-2 family members may serve as effective therapeutic targets in lung cancer. However, the potential of AT-101 as an agent that enhances the therapeutic ratio of radiotherapy varies depending on the lung cancer clone. / Next, we turned to a different approach, focusing on the inhibition of apoptosis instead of its promotion. This work hypothesis was based on previous observations looking at the role of radiation-induced apoptosis by knockdown of Bak and Bax. The radiosensitivity of breast and lung cancer in vitro was increased through autophagy, an alternate type of programmed cell death. Consistently, radiation-induced apoptosis accounts for a minor portion of cell death in irradiated solid tumors. The hypothesis of our work was that apoptosis inhibition would increase radiation-induced autophagy and tumor sensitivity to radiation. To block apoptosis, we used Z-VAD, a broad-spectrum caspase inhibitor, and examined its in vitro and in vivo effects on breast and lung cancer models. Z-VAD markedly radiosensitized breast and lung cancer cells in vitro, with a radiation dose enhancement ratio of 1.31 (P < 0.003). The enhanced tumor cytotoxicity was associated with induction of autophagy. In both breast and lung cancer mice xenograft models, the administration of Z-VAD concurrent with radiation produced a significant tumor growth delay compared with radiation alone and was well tolerated. Interestingly, Z-VAD also had a dramatic antiangiogenic effect when combined with radiation both in vitro and in vivo. Thus, Z-VAD represents an attractive anticancer therapeutic strategy. We further explored the potential of apoptosis inhibition as a way to sensitize cancer to radiation using a more selective chemical, M867, which is a reversible caspase-3 inhibitor. In an in vivo mouse hind limb lung cancer model, the administration of M867 with ionizing radiation was well tolerated, and produced a significant tumor growth delay compared with radiation alone. A dramatic decrease in tumor vasculature and tumor cell proliferation was observed with M867 despite the reduced levels of apoptosis. The radiosensitizing effect of M867 through the inhibition of caspases was validated using a caspase-3/-7 double-knockout (DKO) mouse embryonic fibroblasts (MEF) cell model. Consistent with our previous results, autophagy contributed to the mechanism of increased cell death, following inhibition of apoptosis. Finally, we investigated the mechanism by which radiation triggers autophagy in caspase-3/7-deficient cells, and found the involvement of endoplasmic reticulum (ER) stress. The ER activates a survival pathway, the unfolded protein response, which involves ER-localized transmembrane proteins such as protein kinase-like ER kinase (PERK), inositol-requiring enzyme-1, and activating transcription factor-6. In this study, we found that PERK is essential for radiation-induced autophagy and radiosensitivity in caspase-3/7 double-knockout cells. Irradiation of these cells increased expression of phosphorylated-eIF2a. Similar results were seen after administration of tunicamycin (TM), a well-known ER stress inducer. We found that the administration of TM with radiation in MCF-7 breast cancer cells, which are lacking functional caspase-3 and are relatively resistant to many anticancer agents, enhances radiation sensitivity. Our findings revealed ER stress as a novel potential mechanism of radiation-induced autophagy in caspase-3/7-deficient cells and as a potential strategy to maximize efficiency of radiation therapy in breast cancer. Our data suggested that caspase-3 has a critical role in modulating the PERK/eIF2a pathway after radiation. / Many cancers exhibit multiple deregulations in cell death pathways, allowing for the subsequent promotion of tumor cell survival, and contributing to a relatively low response rate to therapies based on the use of pro-apoptotic strategies. As we have showed, there is a potential for novel anticancer strategies to overcome resistant cancer cells with defective apoptosis machinery in order to improve overall therapeutic outcomes. Such novel approach is to drive cancer cells towards autophagy, as demonstrated by our experiments that studied the effect of radiation on the induction of autophagy in caspase-deficient models. / Doctorat en Sciences biomédicales et pharmaceutiques (Médecine) / info:eu-repo/semantics/nonPublished