<p>The Swedish Cancer Register was used to determine the relative survival rate in colon and rectal cancer and to estimate the occurrence of second cancers related to radiation therapy for rectal cancer. The Swedish Hospital Discharge Register and hospital records were used to estimate the rate of late adverse effects due to radiation therapy for rectal cancer. The whole Swedish population was the source of the survival studies. Patients participating in the Uppsala Trial and the Swedish Rectal Cancer Trial on radiation therapy for rectal cancer constituted the subjects of the studies on late adverse effects and second cancers.</p><p>The main results of the survival analysis revealed a significant improvement in the 5-year relative survival rate for both colon and rectal cancer. During the time period 1960-1999, the survival improved from 39.6% to 57.2% in colon cancer and from 36.1% to 57.6% in rectal cancer.</p><p>Patients irradiated for rectal cancer, in addition to surgery, were at increased risk for a second cancer compared to those treated by surgery alone. This risk increase was mainly found for cancers developing in organs within or adjacent to the irradiated target (relative risk (RR) 2.04; 95% confidence interval (CI) 1.10–3.79). Furthermore, the most important late adverse effects of radiation therapy seem to be those on the gastrointestinal tract, in the form of small bowel obstruction (RR 1.88; 95%CI 1.10–3.20) and abdominal pain (RR 1.92; 95% CI 1.14–3.23). Overall, the benefit of radiation therapy was greater than its drawbacks, as a large reduction in local recurrences and better survival was noted in patients treated preoperatively with irradiation for rectal cancer.</p><p>In conclusion, significant improvements in the survival of patients with colon and rectal cancers have occurred in the last decades, especially in patients with rectal cancer. These improvements probably are related to advances in surgical and adjuvant treatment. The radiation therapy has several drawbacks, however, including an increased risk of second cancers and of bowel obstruction. This emphasises the need to further improve the radiation technique and to select only those patients for radiation therapy who are most likely to benefit from it.</p>

<p>The treatment of rectal cancer is complex and comprises: diagnostic measures; different preoperative treatments; a multitude of surgical and technical choices; possibilities of postoperative treatments and postoperative care and follow up. In this thesis, some aspects of this complex paradigm have been further investigated. One of the most feared complications after rectal cancer surgery is anastomotic leakage. The risk of anastomotic leakage is affected by non-influenceable factors related to the tumour and the patient. In the first paper, the risk of anastomotic leakage in relation to a surgical instrument, the circular stapler, was investigated. The risk of leakage was 7% or 11%, depending on the choice of instrument. In the second paper, a long-term evaluation of survival and local recurrence rates in the Swedish Rectal Cancer Trial was made. Randomisation was to either preoperative radiotherapy followed by surgery or surgery alone. After 13 years median follow-up, survival was 38% in the radiotherapy group and 30% in the surgery alone group. Differences in local recurrence rates were seen in all stages. Most rectal cancer operations carry a high risk of morbidity and mortality. For early stage cancers, a local procedure may be sufficient and in the third paper, population-based results of local excision of rectal cancer were explored. In stage I, cancer specific survival was the same after local excision as after major resection, but the relative survival was lower. The risk of local recurrence was higher after local excision than after resections. In the fourth paper, differences in survival rates in the Nordic countries and Scotland were investigated. The relative excess risk of death was highest in Denmark, but only in the first 90 postoperative days. </p><p>Through applying already existing knowledge and successively introducing new treatments, the results for rectal cancer treatment will be further improved.</p>

Rectal cancer is the eight most common cancer diagnosis in Sweden in both men and women, with almost 2000 new cases per year. Radiotherapy, which is an important treatment modality for rectal cancer, has evolved during the past decades. Diagnostic tools have also improved, allowing better staging and offering information used to make well-founded decisions in multidisciplinary team conferences. In a retrospective study (n=46) with locally advanced rectal cancer (LARC) patients, unfit for chemoradiotherapy, patients were treated with short-course radiotherapy. Delayed surgery was done when possible. Radical surgery was possible in 89% of the patients who underwent surgery (80%). Grade IV diarrhoea affected three elderly patients. Target radiation volume should be reduced in elderly or metastatic patients. In a prospective study (n=68) with LARC patients, magnetic resonance imaging (MRI) and 2-18F-fluoro-2-D-deoxyglucose (FDG) positron emission tomography (PET) were used to determine if FDG-PET could provide extra treatment information. Information from FDG-PET changed the stage of 10 patients. Delineation with FDG-PET generally resulted in smaller target volumes than MRI only. Seven of the most advanced LARC patients in the above cohort were used for a methodological study to determine if dose escalation to peripheral, non-resectable regions was feasible. Simultaneous integrated boost plans with photons and protons were evaluated. While toxicity was acceptable in five patients with both protons and photons, two patients with very large tumours had unacceptable risk for intestinal toxicity regardless of modality. In the interim analysis of the Stockholm III Trial (n=303, studying radiotherapy-fractionation and timing of surgery in relation to radiotherapy) compliance was acceptable and severe acute toxicity was infrequent, irrespective of fractionation. Short-course radiotherapy with immediate surgery tended to give more postoperative complications, but only if surgery was delayed more than 10 days after the start of radiotherapy. Quality-of-life in the Stockholm III Trial was studied before, during and shortly after treatment using the EORTC QLQ-C30 and CR38 questionnaires. Surgery accounted for more adverse effects than radiotherapy in all groups. Postoperatively, the poorest quality-of-life was seen in patients given short-course radiotherapy followed by immediate surgery. No postoperative differences were seen between the two groups with delayed surgery.

The development of new irradiation techniques is presently a very active field of research with increased availability of more sophisticated modalities such as intensity modulated photons (IMRT), protons and light ions. The primary aim of this work is to evaluate if the dose-distributions using IMRT and protons contribute to clinical advantages. A secondary aim is to investigate the potential clinical implication of the increased relative biological effect (RBE) for protons at the end of the Bragg peak. The potential benefits are evaluated using physical dose measures and dose-response models for normal tissue complication probability (NTCP) and tumour control probability (TCP). Comparative treatment planning was performed using three locally advanced tumour types, left-sided node positive breast cancer, hypopharyngeal cancer, and rectal cancer. All studies showed that both IMRT and protons could improve the dose distributions compared to 3D-CRT, and significantly improve treatment results with lower NTCPs and, concerning hypopharyngeal cancer, higher TCP. Protons always resulted in smaller volumes receiving intermediate and low radiation doses. Using protons or IMRT for left-sided node-positive breast cancer, the advantage is a significantly decreased risk for cardiac mortality (from 6.7% to 1%) and radiation induced pneumonitis (from 28.2% to less than 3%) compared to 3D-CRT. For hypopharyngeal cancer, protons and IMRT provide more selective treatment plans, higher TCP since a simultaneous boost technique is feasible, and better parotid gland sparing for several patients. For locally advanced rectal cancer, the NTCP for small bowel is potentially reduced by approximately 50% using IMRT or protons; protons have an even greater potential if the structure of the small bowel is parallel. A variable RBE correction is developed and applied to a clinical proton treatment plan. A significant difference is obtained compared to the commonly accepted RBE correction of 1.1. This indicates that a variable RBE may be of importance in future proton treatment planning. This thesis provides support for increased use both IMRT and proton radiotherapy, although stronger for protons. Therefore, investments in proton facilities with capacity for large clinical trials can be supported.

The Swedish Cancer Register was used to determine the relative survival rate in colon and rectal cancer and to estimate the occurrence of second cancers related to radiation therapy for rectal cancer. The Swedish Hospital Discharge Register and hospital records were used to estimate the rate of late adverse effects due to radiation therapy for rectal cancer. The whole Swedish population was the source of the survival studies. Patients participating in the Uppsala Trial and the Swedish Rectal Cancer Trial on radiation therapy for rectal cancer constituted the subjects of the studies on late adverse effects and second cancers. The main results of the survival analysis revealed a significant improvement in the 5-year relative survival rate for both colon and rectal cancer. During the time period 1960-1999, the survival improved from 39.6% to 57.2% in colon cancer and from 36.1% to 57.6% in rectal cancer. Patients irradiated for rectal cancer, in addition to surgery, were at increased risk for a second cancer compared to those treated by surgery alone. This risk increase was mainly found for cancers developing in organs within or adjacent to the irradiated target (relative risk (RR) 2.04; 95% confidence interval (CI) 1.10–3.79). Furthermore, the most important late adverse effects of radiation therapy seem to be those on the gastrointestinal tract, in the form of small bowel obstruction (RR 1.88; 95%CI 1.10–3.20) and abdominal pain (RR 1.92; 95% CI 1.14–3.23). Overall, the benefit of radiation therapy was greater than its drawbacks, as a large reduction in local recurrences and better survival was noted in patients treated preoperatively with irradiation for rectal cancer. In conclusion, significant improvements in the survival of patients with colon and rectal cancers have occurred in the last decades, especially in patients with rectal cancer. These improvements probably are related to advances in surgical and adjuvant treatment. The radiation therapy has several drawbacks, however, including an increased risk of second cancers and of bowel obstruction. This emphasises the need to further improve the radiation technique and to select only those patients for radiation therapy who are most likely to benefit from it.

The treatment of rectal cancer is complex and comprises: diagnostic measures; different preoperative treatments; a multitude of surgical and technical choices; possibilities of postoperative treatments and postoperative care and follow up. In this thesis, some aspects of this complex paradigm have been further investigated. One of the most feared complications after rectal cancer surgery is anastomotic leakage. The risk of anastomotic leakage is affected by non-influenceable factors related to the tumour and the patient. In the first paper, the risk of anastomotic leakage in relation to a surgical instrument, the circular stapler, was investigated. The risk of leakage was 7% or 11%, depending on the choice of instrument. In the second paper, a long-term evaluation of survival and local recurrence rates in the Swedish Rectal Cancer Trial was made. Randomisation was to either preoperative radiotherapy followed by surgery or surgery alone. After 13 years median follow-up, survival was 38% in the radiotherapy group and 30% in the surgery alone group. Differences in local recurrence rates were seen in all stages. Most rectal cancer operations carry a high risk of morbidity and mortality. For early stage cancers, a local procedure may be sufficient and in the third paper, population-based results of local excision of rectal cancer were explored. In stage I, cancer specific survival was the same after local excision as after major resection, but the relative survival was lower. The risk of local recurrence was higher after local excision than after resections. In the fourth paper, differences in survival rates in the Nordic countries and Scotland were investigated. The relative excess risk of death was highest in Denmark, but only in the first 90 postoperative days. Through applying already existing knowledge and successively introducing new treatments, the results for rectal cancer treatment will be further improved.

BACKGROUND: MRI is increasingly being used for rectal cancer staging. The purpose of this study was to summarize published evidence to determine the accuracy of MRI for T-category, lymph node (LN) metastases, and circumferential resection margin (CRM) involvement in rectal cancer. METHODS: Sensitivity, specificity, and diagnostic odds ratios (DOR) were estimated using hierarchical summary receiver operating characteristics modeling and bivariate random effects modeling. RESULTS: MRI was more specific for CRM (94%, 95%CI 88-97) than for T-category (75%, 95%CI 68-80) and LN’s (71%, 95%CI 59-81) but was more sensitive for T-category (87%, 95%CI 81-92) than for CRM (77%, 95%CI 57-90) and LN’s (77%, 95%CI 69-84). DOR was higher for CRM (56.1, 95%CI 15.3-205.8) than for LN’s (8.3, 95%CI 4.6-14.7) and T-category (20.4, 95%CI 11.1-37.3). CONCLUSIONS: MRI has good accuracy for both CRM and T-category and should be considered for preoperative rectal cancer staging. In contrast, LN assessment is poor on MRI.

BACKGROUND: MRI is increasingly being used for rectal cancer staging. The purpose of this study was to summarize published evidence to determine the accuracy of MRI for T-category, lymph node (LN) metastases, and circumferential resection margin (CRM) involvement in rectal cancer. METHODS: Sensitivity, specificity, and diagnostic odds ratios (DOR) were estimated using hierarchical summary receiver operating characteristics modeling and bivariate random effects modeling. RESULTS: MRI was more specific for CRM (94%, 95%CI 88-97) than for T-category (75%, 95%CI 68-80) and LN’s (71%, 95%CI 59-81) but was more sensitive for T-category (87%, 95%CI 81-92) than for CRM (77%, 95%CI 57-90) and LN’s (77%, 95%CI 69-84). DOR was higher for CRM (56.1, 95%CI 15.3-205.8) than for LN’s (8.3, 95%CI 4.6-14.7) and T-category (20.4, 95%CI 11.1-37.3). CONCLUSIONS: MRI has good accuracy for both CRM and T-category and should be considered for preoperative rectal cancer staging. In contrast, LN assessment is poor on MRI.

In the shark rectal gland (SRG), apical Cl[superscript]- secretion through CFTR channels is tightly coupled to a basolateral K[superscript]+ conductance. The identity of this K[superscript]+ conductive pathway is unknown. Studies were performed in the isolated perfused SRG with 16 K[superscript]+ channel inhibitors at their IC50 and with acidic perfusate. During maximal chloride secretion stimulated by forskolin and IBMX, secretion was inhibited >90% by barium chloride, a non-selective inhibitor of K[superscript]+ channels. Specific inhibitors of calcium sensitive, voltage sensitive, ATP sensitive, and inward rectifying K[superscript]+ channels had no effect on chloride secretion. The inhibitors quinidine, quinine, bupivicaine, anandamide, and low perfusate pH (6.0) abruptly and reversibly inhibited secretion by >90%, consistent with the presence of the Two-Pore-Domain (4TM 2P/KCNK/K2P) family of K+ channels. Degenerate primers were designed to regions of high amino acid homology in known mammal and teleost 4TM 2P K[superscript]+ channel subtypes: TWIK, THIK, TASK, TREK, and TRAAK. PCR with cDNA from several shark tissues identified a putative TASK-1 fragment (394 bp) in shark rectal gland, brain, gill, and kidney. 5and 3 RACE PCR was used to obtain the entire 3 sequence and partial 5 sequence of the shark gene. Genome walking was then used to obtain the remaining 5sequence, including 335 bp of untranslated region sequence upstream of the start codon. The full length clone (1282bp) had an open reading frame encoding a protein of 375 amino acids. This isoform was 80% identical at the amino acid level to the human TASK-1 protein (394 amino acids). Major structural features of the human protein were conserved in the shark ortholog, including the four transmembrane segments (M1-M4), the 2P domains (P1 and P2), short NH2- and long COOH-termini, and an extended extracellular loop between M1 and P1. Shark and human TASK-1 full-length clones were expressed in Xenopus oocytes and studied with two electrode voltage clamp (TEVC) techniques. Both the shark and human TASK-1 channel showed identical current voltage relationships (outward rectifying) with a reversal potential near -90 mV compared to water injected controls. The responses to the inhibitor quinine, and the TASK-1 inhibitor bupivacaine, were identical in shark and human TASK-1. However, shark TASK-1 differed from the human ortholog in two critical responses: response to pH and the metal zinc. The pKa for shark TASK-1 was 7.75 vs. 7.37 for human TASK-1, values that are exceedingly close to the arterial pH for each species, suggesting that TASK-1 channels are regulated closely by the ambient pH. An antibody specific to shark TASK-1 was generated and expression of TASK-1 protein in the rectal gland was confirmed by confocal immuno-fluorescent microscopy which revealed localization to the basolateral membrane, with some apical staining. Shark rectal gland TASK-1 appears to be the major K[superscript]+ channel coupled to secretion in the SRG, is the oldest 4TM 2P family member identified to date, and is the first TASK-1 channel identified to play an essential role in chloride secreting epithelia.

Objective: The rectal mucosa is highly susceptible to HIV infection. Mucosal fluid contains soluble immune proteins that influence HIV infection, and previous studies have shown unique mucosal protein expression in HIV-exposed seronegative (HESN) populations, which may contribute to reduced HIV susceptibility. However, the key correlates of susceptibility at the rectal mucosa have not been well defined, which is a critical knowledge gap for our understanding of HIV pathogenesis. Methods: Rectal lavage from low risk men was screened for HIV-neutralizing activity in a TZM-bl reporter cell line against an R5-tropic HIV virus. Label-free tandem mass spectrometry was used to characterize soluble proteins within rectal lavage samples from a low-risk cohort of men (n=15), and HESN men who have sex with men (MSM; n=25). Protein expression between populations was compared using adjusted t tests (p<0.05), and was interpreted using hierarchical clustering and DAVID biofunctional analysis. Protein expression was further analyzed using survey data on sexual behaviours. Proteins associated with the HESN population were screened for antiviral activity in TZM-bl and PBMC culture against an R5- and X4-tropic virus. Major Results: Rectal mucosal fluid was able to inhibit HIV infection in vitro by 40% (p<0.05). Mass spectrometry identified 30/341 (9%) proteins deferentially expressed (DE) in HESN MSM. DE proteins held functions in immunity (p=6.68x10-6, p=0.001) and epithelial barrier development (p=1.81x10-4; p=0.01); notably, specific antiproteases were elevated in HESN secretions, two of which were screened for antiviral activity. Serpin B4 (+2.52 L2FD; p=1.09x10-5), showed significant inhibition of HIV in TZM-bl (45% BaL, 34% IIIB; p<0.05) and PBMC culture (37% BaL, 49% IIIB; p<0.05); cystatin A (+1.52 L2FD; p=1.40x10-3) showed no inhibitory effects. Serpin B4 expression was not associated with frequency of oral intercourse (p=0.32), partner viral load (r=0.16; p=0.29) or presence of HIV neutralizing IgA in secretions (p=0.52). Conclusions: This thesis reports the use of proteomics to understand HIV-susceptibility at the rectal mucosa, and identified serpin B4 as a novel antiviral immune correlate in a population of HESN MSM. These results may help guide future studies of prevention technologies, such as microbicides or vaccines, which would ultimately help limit the spread of HIV. / February 2016