The clinical introduction of proton therapy requires an extensive analysis of its benefits compared to conventional radiotherapy and a detailed analysis of possible uncertainties which might have serious consequences for patient treatment. In the first part of the presented thesis, the expected toxicities were evaluated for a treatment of head and neck cancer patients using a biologically adapted dose escalation schedule with photon and proton therapy. The feasibility of the dose escalation schedule could be demonstrated for both photon and proton therapy, since only a small increase in toxicity risk occurred for most toxicities. However, the expected toxicity risks were in most cases smaller with proton therapy. Furthermore, a higher benefit was found for patients with primary tumour locations in the upper head and neck area, who thus might be preferably referred to proton therapy. In the second part of this thesis, an extensive analysis of the impact of tumour motion in lung cancer treatment with active-scanning proton therapy was conducted. It could be shown, that dose degradations were small for tumour motion amplitudes below 5 mm. Parameters like the target volume concept, the optimisation approach, changes in the motion pattern and application sequence times had additional impact on the dose degradation. However, their magnitude was patient specific. Since not all parameters can be assessed before treatment, e.g. the motion pattern during treatment, prospective estimations should be supplemented by retrospective analyses. / Die Einführung der Protonentherapie in die klinische Praxis erfordert umfassende Analysen ihrer Vor- und Nachteile im Vergleich zur konventionellen Photonentherapie sowie detaillierte Untersuchungen der Auswirkungen von Unsicherheiten in der Therapieapplikation. Im ersten Teil der vorliegenden Arbeit wurden die zu erwartenden Nebenwirkungen bei der Behandlung von Patienten mit Kopf-Hals-Tumoren mit einem biologisch-adaptierten Fraktionierungsschema inklusive Dosiseskalation mit Photonen- und Protonentherapie evaluiert. Dabei konnte gezeigt werden, dass die Dosiseskalation sowohl mit Photonen- als auch Protonentherapie angewandt werden kann, da die Wahrscheinlichkeit für das Auftreten von Nebenwirkungen in den meisten Fällen kaum erhöht wurde. Weiterhin wurden die Nebenwirkungswahrscheinlichkeiten mit der Protonentherapie im Vergleich zur Photonentherapie reduziert. Dies war vor allem für Patienten mit Tumoren im oberen Kopf-Hals-Bereich der Fall. Diese könnten daher bevorzugt zur Protonentherapie überwiesen werden. Darüber hinaus wurde im zweiten Teil der Arbeit eine umfassende Analyse des Einflusses der Tumorbewegung auf die Dosisverteilung bei Behandlung von Lungentumoren mit aktiver Protonenstrahlformierung durchgeführt. Dabei zeigte sich, dass Dosisdegradierungen bei Bewegungsamplituden unter 5mm gering sind. Parameter wie das Zielvolumenkonzept, Veränderungen des Bewegungsmusters oder der Applikationszeiten nehmen zusätzlich Einfluss auf die Dosisdegradierung, allerdings in unterschiedlichem Maß für individuelle Patienten. Da nicht alle Parameter vor Behandlung bekannt sein können, sollten prospektive Dosisabschätzungen durch retrospektive Analysen ergänzt werden.

L’inclusion récente de la profondeur d’invasion (PI) dans la classification des carcinomes épidermoïdes de la cavité orale de l’American Joint Committee on Cancer (AJCC) a des répercussions cliniques majeures. Plusieurs études ont récemment évalué la fiabilité de diverses modalités d’imagerie et techniques de biopsie pour mesurer la PI en préopératoire. L’objectif premier de ce mémoire est de réviser systématiquement la littérature et comparer les différentes méthodes décrites de mesure de PI en préopératoire pour les carcinomes épidermoïdes de la langue mobile. Le second objectif est d’étudier la précision et la fiabilité de la mesure de PI sur une biopsie au poinçon dans les carcinomes épidermoïdes de stade in situ (Tis)-T1-T2, N0 de la langue mobile. Une revue systématique a été effectuée en suivant le guide PRISMA[1]. Les études évaluant la fiabilité de la PI mesurée sur la biopsie ou l’imagerie médicale, en les comparant à la PI histopathologique finale, ont été inclues dans une méta-analyse afin d’obtenir des coefficients de corrélation combinés pour chaque modalité d’imagerie. L’imagerie par résonnance magnétique (IRM) s’est avérée être la modalité d’imagerie la mieux étudiée et présente une bonne fiabilité. Le computed tomography (CT) scan est peu étudié, mais semble moins fiable. L’échographie linguale ne peut être comparée à ces deux modalités d’imagerie car elle est plus fréquemment utilisée pour mesurer l’épaisseur tumorale que la PI. La seconde étude est une preuve de concept prospective. Un poinçon profond a été utilisé pour échantillonner la portion la plus profonde de carcinomes épidermoïdes de la langue mobile de stade Tis-T1-2, N0 chez 27 patients. Des coefficients de corrélation de Spearman ont été calculés entre la PI estimée à la palpation manuelle, mesurée à la biopsie, et à l’histopathologie. La sensibilité et la spécificité de la biopsie au poinçon pour distinguer le Tis du carcinome épidermoïde invasif ont été calculées. Bien que la PI mesurée à la biopsie ne corrèle pas fortement avec la PI histopathologique, cette preuve de concept est limitée par la taille d’échantillon. La biopsie au poinçon semble toutefois être un outil fiable pour distinguer le Tis de l’invasif. D’autres études sont nécessaires avant de pouvoir recommander l’utilisation systématique de la biopsie pour décider en préopératoire si un évidement cervical électif est nécessaire. / The inclusion of depth of invasion (DOI) in the American Joint Committee on Cancer’s staging system for oral cavity squamous cell carcinoma (SCC) has major clinical impacts. Recent studies have evaluated the reliability of imaging modalities and biopsy techniques to measure DOI preoperatively. The first objective of this master’s thesis is to systematically review and compare the preoperative DOI measurement methods that have been studied so far in oral tongue SCC (OTSCC). The second objective is to prospectively study the precision and reliability of punch biopsy to measure DOI preoperatively in early (in situ (Tis)-T1-T2, N0) OTSCC, and its ability to distinguish Tis from invasive carcinoma. A systematic review was conducted according to the PRISMA guidelines. Studies that evaluated the reliability of DOI measured on biopsy or imaging (rDOI) by comparing it to DOI on histopathology (pDOI) were included in a meta-analysis to obtain pooled correlation coefficients for each imaging modality. Overall, magnetic resonance imaging (MRI) is the better studied modality. It has a good reliability to measure preoperative rDOI in OTSCC. CT is less studied but appears to be less reliable. Ultrasound (US) cannot be compared to these imaging modality as it has been used more often to measure tumor thickness (TT) than DOI. The second study is a prospective proof-of-concept. A deep punch biopsy was used to sample tumors preoperatively in the deepest part of the tumor in 27 patients with early (Tis-T12, N0) oral tongue squamous cell carcinoma. Spearman’s correlations were calculated between DOI measured on digital palpation (cDOI), biopsy (bDOI) and final pDOI. The sensitivity and specificity of punch biopsy to distinguish Tis from invasive carcinoma was also calculated. Although bDOI does not seem to correlate strongly with pDOI, this proof-of-concept was limited by a small sample size. Punch biopsy appears to be a reliable tool to distinguish Tis from invasive carcinoma. Further studies on punch biopsy are needed to recommend its use to evaluate pDOI preoperatively and determine whether elective neck dissection is necessary in early OTSCC.

Indiana University-Purdue University Indianapolis (IUPUI) / Shoulder pain was constantly reported as a problematic symptom causing dysfunction and quality of life interference after neck dissection in head and neck cancer patients. Due to a lack of conceptual framework and inconsistency of instrument selection, a comparison among previous studies was almost impossible, making it difficult to understand the phenomenon. The current study applied the University of California, San Francisco School of Nursing Symptom Management Model. The purposes of the study were to (a) describe the symptom experience of shoulder pain at 1 month after neck dissection, (b) describe the relationships among symptom experience of shoulder pain, functional status, and quality of life, and (c) identify the contextual variables, concurrent symptoms, and/or adherence predicting symptom experience of shoulder pain, functional status, and/or quality of life. This was a descriptive study with a convenience sample of head and neck cancer patients. The data were collected via a medical record review, a self-administered survey, and a physical examination. The data from 29 patients were entered for descriptive statistics, Pearson correlations, and multiple regressions. At 1 month after surgery, 62% of patients reported they had shoulder pain at some point within a week. Their shoulder pain was from mild to moderate. Fifty-nine percent complained that shoulder pain bothered them about the moderated level. In the final model, symptom experience, shoulder pain, was significantly correlated with one outcome, active shoulder abduction, but not the other, total quality of life, generic quality of life, and head and neck quality of life. Active shoulder abduction was significantly correlated with three quality of life measures. Adding significant predictors of symptom experience and outcomes into the final model, there is a potential that the model would be useful to guide treatment strategies. Treatment for myofascial pain of the levator scapulae could relieve shoulder pain after neck dissection and improve head and neck quality of life. Those with level V dissection were high risk populations of developing shoulder pain. Risk factors of quality of life, which were depression, loss of sensation, and radiation would describe how an intervention could change or unchange the patient’s life.

Purpose: The Hedgehog-signalling pathway (Hh) is frequently active in head and neck squamous cell carcinoma (HNSCC). Overexpressed Hh associates with poor prognosis. The Hh inhibitor vismodegib targets smoothened (SMO) and, based on molecular data, may prevent resistance to EGFR targeting. Methods: To elucidate potential roles of vismodegib in HNSCC therapy, its sole effects and those combined with cisplatin, docetaxel, and cetuximab on HNSCC cell lines were assessed by MTT metabolisation and BrdU incorporation. Colony formation (CF) of primary HNSCC cells was studied utilizing the FLAVINO-protocol. Combinatory effects were analysed regarding antagonism, additivity or synergism. Associations between the ex vivo detected mode of action of vismodegib with other treatments related to patient characteristics were assessed and progression-free survival (PFS) in patient groups compared using Kaplan-Meier curves. Results: Vismodegib suppressed BrdU incorporation significantly stronger than MTT turnover; CF was significantly inhibited at ≥20 µM vismodegib while concentrations <20 µM acted hormetic. Combining 20 µM vismodegib plus docetaxel (T), cisplatin (P), and cetuximab (E), additively enhanced antitumoral activity in HNSCC samples from patients with superior PFS highlighting a potential role for ex-vivo testing of this combination for use as a prognostic classifier. Conclusion: We provide ex-vivo evidence for vismodegib’s potential in HNSCC therapies especially if combined with cetuximab, cisplatin and docetaxel.:Abkürzungsverzeichnis 1 Einleitung 1.1 Kopf-Hals-Tumore 1.1.1 Therapie von Kopf-Hals-TumoreN 1.1.2 Limitationen der etablierten Therapien 1.2 Eingesetzte Chemotherapeutika 1.2.1 Cisplatin 1.2.2 Docetaxel 1.2.3 Cetuximab 1.3 Hedgehog-Signaltransduktionsweg 1.3.1 Hedgehog-Signalweg und Karzinogenese 1.3.2 Vermittlung von Tumortherapieresistenz durch den Hedgehog-Signalweg 1.3.3 Zielgerichtete Tumortherapie durch Blockade des Hedgehog-Signalweges 1.4 Vismodegib 1.5 Ex-Vivo-Chemoresponse-Testung mittels FLAVINO-Assay 1.6 Zusammenfassung der Rationale der Untersuchung 1.7 Aufgabenstellung der Promotionsarbeit 2 Publikation 2.1 Reduzierte Proliferation und Koloniebildung von Plattenepithelkarzinomen der Kopf Hals Region unter dualer Inhibition des EGFR- und Hedgehog-Signalweges 3 Zusammenfassung der Arbeit 4 Literaturverzeichnis 5 Anlagen 5.1 Darstellung des Eigenanteils 5.2 Erklärung über die eigenständige Abfassung der Arbeit 5.3 Lebenslauf 5.4 Publikationen 5.5 Danksagung

Background: The landmark EXTREME trial established cisplatin, 5-fluorouracil and cetuximab (PFE) as first-line chemotherapy (1L-ChT) for recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC). We were interested in outcome differences of R/M HNSCC in 1L-ChT and factors influencing outcome in certain subgroups, especially patients receiving PFE, and the value of PFE compared to other 1L-ChT regimens to provide real world evidence (RWE). Methods: For this retrospective monocentric study, 124 R/M HNSCC patients without curative surgical or radiotherapy options receiving at least one cycle of 1L-ChT were eligible. We analyzed their outcome using Kaplan-Meier plot and Cox regression to identify predictors for prolonged survival. Results: Subgroups benefiting significantly from PFE were patients suffering from an index HNSCC outside the oropharynx. The PFE regimen proved to be superior to all other 1L-ChT regimens in clinical routine. Significant outcome differences between PFE treatment within or outside controlled trials were not seen. Conclusion: This retrospective analysis provides RWE for factors linked to improved outcome. Subgroup analyses highlight the lasting value of PFE among the growing spectrum of 1L-ChT. Importantly, fit smokers with high level alcohol consumption benefit from PFE; considering the patient’s lifestyle factors, PFE should not be ignored in decision-making.

Background: Standardized staging procedures and presentation of oral squamous cell carcinoma (OSCC) patients in multidisciplinary tumor boards (MDTB) before treatment and utilization of elective neck dissection (ND) are expected to improve the outcome, especially in local advanced LAOSCC (UICC stages III–IVB). As standardized diagnostics but also increased heterogeneity in treatment applied so far have not been demonstrated to improve outcome in LAOSCC, a retrospective study was initiated. Methods: As MDTB was introduced into clinical routine in 2007, 316 LAOSCC patients treated during 1991-2017 in our hospital were stratified into cohort 1 treated before (n=104) and cohort 2 since 2007 (n=212). Clinical characteristics, diagnostic procedures and treatment modality of patients were compared using Chi-square tests and outcome analyzed applying Kaplan-Meier plots and log-rank tests as well as Cox proportional hazard regression. Propensity scores (PS) were used to elucidate predictors for impaired distant metastasis-free survival (DMFS) in PS-matched patients. Results: Most patient characteristics and treatment modalities applied showed insignificant alteration. Surgical treatment included significantly more often resection of the primary tumor plus neck dissection, tracheostomy and percutaneous endoscopic gastrostomy tube use. Cisplatin-based chemo-radiotherapy was the most frequent. Only insignificant improved disease- (DFS), progression- (PFS) and event-free (EFS) as well as tumor-specific (TSS) and overall survival (OS) were found after 2006 as local (LC) and locoregional control (LRC) were significantly improved but DMFS significantly impaired. Cox regression applied to PS-matched patients elucidated N3, belonging to cohort 2 and cisplatin-based chemo-radiotherapy as independent predictors for shortened DMFS. The along chemo-radiotherapy increased dexamethasone use in cohort 2 correlates with increased DM. Conclusions: Despite standardized diagnostic procedures, decision-making considering clear indications and improved therapy algorithms leading to improved LC and LRC, shortened DMFS hypothetically linked to increased dexamethasone use had a detrimental effect on TSS and OS.

Background: About five to 10% of cancers in the head and neck region are neck squamous cell carcinoma of unknown primary (NSCCUP). Their diagnosis and treatment are challenging given the risk of missing occult tumors and potential relapse. Recently, we described human papillomavirus (HPV)-related NSCCUP-patients (NSCCUP-P) as a subgroup with superior survival. However, standardized diagnostic workup, novel diagnostic procedures, decision-making in the multidisciplinary tumor board (MDTB) and multimodal therapy including surgery and post-operative radio-chemotherapy (PORCT) may also improve survival. Methods: For assessing the impact of standardized diagnostic processes simultaneously established with the MDTB on outcome, we split our sample of 115 NSCCUP-P into two cohorts treated with curative intent from 1988 to 2006 (cohort 1; n = 53) and 2007 to 2018 (cohort 2; n = 62). We compared diagnostic processes and utilized treatment modalities applying Chi-square tests, and outcome by Kaplan–Meier plots and Cox regression. Results: In cohort 2, the standardized processes (regular use of [18F]-FDG-PET-CT imaging followed by examination under anesthesia, EUA, bilateral tonsillectomy and neck dissection, ND, at least of the affected site) improved detection of primaries (P = 0.026) mostly located in the oropharynx (P = 0.001). From 66.0 to 87.1% increased ND frequency (P = 0.007) increased the detection of extracapsular extension of neck nodes (ECE+) forcing risk factor-adapted treatment by increased utilization of cisplatin-based PORCT that improved 5-years progression-free and overall survival from 60.4 and 45.3 to 67.7% (P = 0.411) and 66.1% (P = 0.025). Conclusions: Standardized diagnostic workup followed by ND and risk-factor adapted therapy improves survival of NSCCUP-P.

Neben Zigarettenrauchen und chronischem Alkoholkonsum scheinen genetische Faktoren bei der Entstehung und im Verlauf der Kopf-Hals-Karzinom Erkrankung bedeutsam zu sein. Genvariationen in den Enzymen, die zigarettenrauch-assoziierte Karzinogene (Glutathion-S-Transferase, GST, Cytochrom P450, CYP) metabolisieren, sowie Genvariationen in immunregulierenden Zytokinen (Tumor-Nekrose-Faktor) könnten Grund dieser Beeinflussung sein. Ziel dieser Studie war es, genetische Wirtsfaktoren zu identifizieren, die das Erkrankungsrisiko und das Tumorverhalten bzw. den Krankheitsverlauf von Plattenepithelkarzinomen im oberen Aerodigestivtrakt beeinflussen. Wir beschreiben den Zusammenhang zwischen Genotypen an GSTM1, M3, T1, P1, CYP2D6, 1A1, 2E1 und TNF Mikrosatelliten-Genorten und der Krankheitsentstehung sowie Tumorcharakteristika wie der initialen Tumorgröße, der Halslymphknotenmetastasierung, dem histologischen Differenzierungsgrad des Tumorgewebes und dem rezidivfreien Überleben bei 465 Patienten. Die Genotypen wurden aus der Leukozyten-DNA mittels PCR in Kombination mit Restriktionsenzymverdauungen und Elektrophoresetechniken identifiziert. Sowohl bei den Genvariationen in den entgiftenden Enzymen als auch bei den TNF Mikrosatelliten-Polymorphismen konnten Risikogenotypen festgestellt werden. Die Beeinflussung des Krankheitsverlaufs war teilweise deutlicher ausgeprägt, als die Beeinflussung der Krankheitsentstehung. Patienten mit Mehrfachkarzinomen wiesen die stärkste Anhäufung von Risikogenotypen auf. In dieser Studie konnte erstmals gezeigt werden, daß individuelle Genotypkonstellationen die Entstehung und das Verhalten von Plattenepithelkarzinomen im oberen Aerodigestivtrakt beeinflussen. / Cigarette smoking and alcohol consumption are the main risk factors for the development of head and neck cancer. Additionally, genetic factors seem to be influential. Gene variations in detoxifying enzymes such as glutathione S-transferase (GST) and cytochrome P450 (CYP) and variations in immune regulating proteins like tumor necrosis factor (TNF) are candidate genes. Accordingly, we have examined, in 465 patients with squamous cell carcinoma (SCC) of the head and neck, associations between GSTM1, GSTT1, GSTM3, GSTP1, CYP2D6, CYP1A1, CYP2E1 genotypes and TNF microsatellite polymorphisms and cancer susceptibility, outcome parameters like tumor extension, histological grade, and presence of lymph nodes, and tumor recurrence. Genotypes were determined by PCR; logistic regression and a step-wise model were used to investigate the influence of the individual genes. Individual genotypes in the detoxifying enzymes and TNF were associated with altered cancer risk. The influence on tumor behavior was partially stronger. Patients suffering multiple head and neck cancer showed the highest cumulation of risk mediating genotypes. The data demonstrate site-dependent associations between GST, CYP and TNF genotypes and tumor susceptibility, tumor extension, differentiation, and lymph node involvement, and tumor recurrence in SCC of the head and neck.

Plattenepithelkarzinome der Kopf-Hals-Region sind durch einen aggressiven Krankheitsverlauf mit häufigem Auftreten von Lokalrezidiven und Zweitkarzinomen gekennzeichnet. Molekulare Veränderungen des Tumorrandes und der Tumor benachbarten Gewebe könnten in Ergänzung zur Histopathologie eine kurative chirurgische Tumorextirpation bestätigen. Wir untersuchten die Telomeraseaktivität in verschiedenen Entfernungen vom Tumorzentrum um ihre Verwendung als molekularen Marker zu prüfen. Wir untersuchten 80 kryokonservierte Gewebeschnitte von 40 Patienten mit einem Plattenepithelkarzinom im Kopf-Hals-Bereich, davon 33 karzinomfreie Tumorrandgewebe. 50% der 20 karzinomhaltigen Gewebe, 28 % der karzinomfreien Tumorrandgewebe und 35 % der tumorfernen Proben waren telomerasepositiv. Der Vergleich ergab keinen statistisch signifikanten Unterschied. Es konnte keine sichere Korrelation zwischen der Telomeraseaktivität in den untersuchten Geweben mit dem weiteren Krankheitsverlauf gefunden werden, allerdings zeigte die Telomerasepositivität in karzinomfreien Tumorrändern die Tendenz, mit einer besseren Prognose zu korrespondieren. Unsere Befunde sollten an einer größeren und homogeneren Patientengruppe überprüft werden. / Squamous cell carcinomas of the head-neck region are characterised by an aggressive course of disease and a strong tendency to loco-regional recurrence and second primary tumours. As a complement to histopathology, molecular changes of tumour marginal and tumor distant tissue may confirm curative surgical tumour extirpation. We tested telomerase activity at different distances to the tumour centre of squamous cell carcinomas to consider the use for molecular marker. We examined 80 cryo-conserved tissue samples from 40 patients with a squamous cell carcinoma of the head-neck region, among them 33 carcinoma-free margin tissues. 50 % of the carcinoma centres, 28 % of the carcinoma-free margin tissues and 35% of the tumour distant samples were telomerase-positive. The comparison showed no statistically significant difference. We have found no reliable correlation between telomerase activity in the carcinoma-free margin tissues and the further course of disease, but telomerase positivity in carcinoma-free tumour margins tended to correlate with a better prognosis. Confirmation of the results in a larger and more homogeneous patient group is needed.

Introduction: Le gène O6-méthylguanine-ADN méthyltransferase (MGMT) code pour une enzyme spécifique réparatrice de l’ADN qui protège les cellules de la toxicité des agents alkylants. Ainsi, l’activité du MGMT est un mécanisme majeur de résistance aux agents alkylants. Il a été démontré qu’une diminution de l’expression du gène MGMT par une hyperméthylation du promoteur résulte en une amélioration de la survie chez les patients avec certains types de tumeurs qui sont traitées avec des agents chimiothérapeuthique alkylants. Objectifs: Déterminer la prévalence de la méthylation du gène MGMT chez des patients avec des cancers épidermoïdes localement avancés de la sphère ORL traités avec chimioradiothérapie et évaluer l’impact de cette méthylation sur la survie. Méthodes: Sur 428 patients consécutifs, traités avec chimioradiothérapie à notre institution et suivis pour un période médiane de 37 mois, 199 spécimens chirurgicaux paraffinés ont été récupérés. L’ADN était extrait et modifié par le traitement au bisulfite. Une réaction en chaîne de la polymérase, spécifique à la méthylation était entreprise pour évaluer l’état de méthylation du promoteur du gène du MGMT. Les résultats de laboratoire étaient corrélés avec la réponse clinique. L’analyse statistique était exécutée à l’aide du test de Fisher pour les données catégoriques et à l’aide des courbes de Kaplan-Meier pour les échecs au traitement. Résultats : Des 199 extraits d’ADN initiaux, 173 (87%) étaient modifiés au bisulfite avec succès. Des ces spécimens modifiés, 71 (41%) ont démontré une hyperméthylation du MGMT. Pour les cas de méthylation et nonméthylation du MGMT, les caractéristiques des patients n’étaient pas significativement différentes. Les taux de réponse étaient 71 et 73% (p=NS) respectivement. Le contrôle locorégional était respectivement 87 et 77% (p=0.26), la survie sans maladie était 80 et 60% (p=0.38), la survie sans métastase à distance était 92 et 78% (p=0.08) et la survie globale était 64 et 62% (p=0.99) à 3 ans. Conclusions : L’état de méthylation du MGMT est fortement prévalent (41%) et semble avoir un possible impact bénéfique sur la survie quand la chimioradiothérapie est administrée aux patients avec des stades avancés de cancers tête et cou. / Background: The O6-methylguanine-DNA methyltransferase (MGMT) gene encodes a specific DNA repair enzyme that protects cells from toxicity of alkylating agents. Thus, MGMT activity is a major mechanism of resistance to alkylating drugs. It has been shown that decreased MGMT gene expression by promoter hypermethylation results in improved survival in patients with certain types of tumors that are treated with alkylating chemotherapeutic agents. Objectives: To determine the prevalence of MGMT methylation in patients with locally advanced Head and Neck Squamous Cell Carcinoma (HNSCC) treated with chemoradiation therapy and to evaluate the impact of this methylation on survival. Methods: Out of 428 consecutive patients treated with chemoradiation therapy at our institution and followed for a median of 37 months, 199 paraffin embedded biopsy or surgical specimens were retrieved. DNA was extracted and subjected to bisulfite treatment. A methylation specific PCR (MSP) was conducted to assess the methylation status of the MGMT gene promoter. Laboratory data was correlated with clinical response. Statistical analysis was performed using Fisher’s test for categorical data and Kaplan-Meier’s curves and logrank statistics for failure times. Results: From the initial 199 DNA extracts, 173 (87%) were successfully modified with bisulfite. Out of these, 71 (41%) demonstrated hypermethylation of MGMT. For MGMT methylated cases and nonmethylated cases, patients characteristics were not significantly different. Response rates were 71 and 73% (p=NS), respectively. Local control rate (LCR) was respectively 87 and 77% (p=0.26), Disease-free survival (DFS) was 80 and 60% (p=0.38), distant metastasis free survival (DMFS) was 92 and 78% (p=0.08) and overall survival (OS) was 64 and 62% (p=0.99) at 3 years respectively. Conclusions: MGMT methylation status is highly prevalent (41%) and seems to have a possible beneficial impact on survival when chemoradiation therapy is given to patients with advanced stage HNSCC.