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Background: Adaptive radiotherapy (ART) can counteract the changes in initial dose distribution caused by volume change of target volumes during radiotherapy in patients with oropharyngeal cancer (OPC). The time-consuming nature and high costs of ART highlight the need for identification of suitable patients to make implementation of ART in clinical practice possible. Diffusion weighted MRI (DW-MRI), a functional imaging technique allows quantification of the water diffusion by the apparent diffusion coefficient (ADC), which inversely reflects the tissue cellularity. Aim: The aim of this research was to investigate if DW-MRI ADC values can help in selecting OPC patients that will need replanning during their treatment. Methods: Patients who received radiotherapy (RT) for OPC at university hospitals Leuven were analyzed retrospectively. Primary tumor volume was delineated on gadolinium-enhanced T1-weighted MRI, which was registered to the planning CT, and were validated by a radiation-oncologist with experience in HNC: this was done twice, once before treatment started (week 0) and once during treatment (week 4). Open-source Pyradiomics software was used by experienced radiologist to extract mean and median ADC values of both MRIs. Delta (Δ) ADC was calculated using the formula: Δ ADC = ADC mean (MRI week 0) – ADC mean (MRI week 4). Patient, tumor and treatment characteristics were obtained from the electronic patient record system KWS. Follow-up period started from diagnosis until 3 years after diagnosis. All statistical tests were performed using TIBCO Statistica software (version 14) with statistical significance defined as p < 0,05. Results: 108 patients were included. The studied population was predominant male (85,19%) with a mean age of 60,8 years and a mean initial primary tumor volume of 25,32 cc. Mean 3-year overall survival (OS) and locoregional control (LRC) was 886,00 days and 788,89 days respectively. 32,41% died within 3 years after start of treatment. 23,15% of patients suffered from recurrent disease within 3 years after start of treatment. High treatment ADC values were correlated with higher LRC. Both high mean and median ADC values during treatment were correlated with a greater volume decrease of the primary tumor during RT (p = 0,020860 and p = 0,027487 respectively). No significant differences were found between the pretreatment DW-MRI parameters and volumetric change during treatment. Conclusion: Based on this analysis, pretreatment DW-MRI cannot be used to distinguish between patients who would benefit from ART and who would not. There is a significant difference with treatment ADC values that is repeatedly confirmed. Further investigations are necessary to investigate if DW-MRI during treatment could play a role in identifying patients for ART.

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Objective: In this retrospective study we aimed to analyze oncological outcomes after treatment for oropharyngeal squamous cell carcinoma and to evaluate patient- and disease-related prognostic factors for outcome. Material and Methods: In 440 patients with oropharyngeal squamous cell carcinoma treated in the University Hospital of Leuven, the data submitted to the Belgian Cancer Registry were downloaded again and overall survival, disease-free survival and disease-specific survival were calculated. Univariable and multivariable analysis were used to identify possible prognostic factors for oncologic outcomes. Results: Five-year overall survival (OS), disease-free survival (DFS) and disease-specific survival (DSS) estimates were 45.69%, 41.35% and 85.56% respectively. Several patient and disease-related characteristics affect survival outcome in individuals diagnosed with oropharyngeal squamous cell carcinoma. Conclusions: Higher clinical T-stage is an independent negative prognostic factors for overall survival and disease-free survival. Active tobacco abuse was found to be the only independent prognostic factor that negatively affects all endpoints in patients with oropharyngeal squamous cell carcinoma.