ESTRO 2021 Abstract Book

S27

ESTRO 2021

Copenhagen, Denmark; 10 Aarhus University Hospital, Department of Experimental Oncology and Department of Oncology, Aarhus, Denmark; 11 Odense University Hospital, Laboratory of Radiation Physics, Odense, Denmark; 12 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark; 13 Princess Margaret Cancer Centre, Department of Medical Oncology, Toronto, Canada; 14 Princess Margaret Cancer Centre, Department of Otolaryngology - Head and Neck Surgery, Toronto, Canada; 15 Princess Margaret Cancer Centre, Department of Biostatistics, Toronto, Canada Purpose or Objective We compare outcomes in two large-scale HPV-positive (HPV+) oropharynx cancer (OPC) cohorts treated with definitive radiotherapy/chemo-radiotherapy (RT/CRT) and contemporary RT techniques and doses. Materials and Methods HPV+ OPC treated with definitive RT/CRT between 2007-2015 in two distinct cohorts were included: one was institutional (C1) representing one of two cancer centers within a population jurisdiction and received 80% of the region’s referrals, and the other nationwide (C2). Tumor-HPV-status was determined according to p16 immunohistochemistry (p16pos>70% tumor cells). Locoregional failure (LRF), distant metastasis (DM), and overall survival (OS) were compared. Multivariable analysis (MVA) with Cox Proportional-Hazards regression was used to calculate adjusted hazard ratio (aHR) with 95% confidence interval (95% CI), adjusting for cohort, age, gender, performance status (PS), smoking pack-years, T- and N-category and chemotherapy. Results Compared to C1 (n=701), C2 (n=1174) comprised more females (24% vs 16%) and heavier smokers (median 15 vs 10 pack-years), more lower T-categories (T1-2: 77% vs 56%), N-categories (N0-N1: 77% vs 66%), and stage groups (stage I: 63% vs 44% (all p<0.001). C1 used standard fractionation CRT in 69% (481) of patients, and 31% (220) received altered fractionation RT-alone. All C2 patients had 6 fractions/week RT; 96% (1129) received Nimorazole (NIM) and 73% (856) weekly Cisplatin. C2 had shorter overall treatment time (p<0.001), lower gross tumor (66-68 vs 70 Gy) and elective neck (50 vs 56 Gy) doses. Median follow-up was 4.8 years. C2 had higher 5-year LRF (13% vs 7%, aHR=0.47 [0.34-0.67]) and OS (85% vs 80%, aHR=1.30 [1.01-1.68]), but similar DM (7% vs 12%, aHR=1.32 [0.95-1.82]). Smoking pack-years (>30) increased risk of LRF (aHR 1.55 [1.05-2.29]) and overall death (aHR 1.86 [1.34-2.59]) but not DM (p=0.31). T- and N-category retained independent prognostic impact for all outcomes, and concurrent chemotherapy significantly improved outcome for the group of patients receiving CRT: LRF (aHR 0.56 [0.39-0.82]), DM (aHR 0.70 [0.50-1.00]) and OS (aHR 0.39 [0.29-0.52]). Conclusion We observed similar and exemplary outcomes for these large population-based cohorts of patients with p16+ OPC treated with primary RT/CRT and contemporary RT techniques and doses. Concurrent chemotherapy was a strong, independent prognostic factor for all endpoints and our findings underscore the need for a very careful approach to de-intensification of treatment for this disease. PH-0052 Do head and neck cancer patients in randomized trials represent the population in daily practice? J. Kaanders 1 , S. van den Bosch 1 , J. Kleijnen 2 1 Radboudumc, Radiation Oncology, Nijmegen, The Netherlands; 2 Maastricht University, School for Public Health and Primary Care (CAPHRI), Maastricht, The Netherlands Purpose or Objective Randomized controlled trials have strict eligibility criteria. If these criteria deviate too much from patient and tumor characteristics in the general population, it can hamper adoption of the new treatment in daily practice. This may be of special relevance in head and neck cancer (HNC) because life style factors of these patients are associated with multiple co-morbidities which may preclude inclusion in clinical trials. This systematic review investigates if head and neck cancer patients in randomized trials are representative for the population in daily practice. Materials and Methods A systematic literature search was performed with the following inclusion criteria: published randomized controlled trials on non-metastasized primary HNC testing a therapeutical intervention to improve oncologic outcome; total sample size ≥100 patients; studies published from 2009 to 2019. Databases searched were: MEDLINE and Epub Ahead of Print; Embase; Cochrane Central Register of Controlled Trials; and ClinicalTrials.gov. Information retrieved from the publications included: 1. HNC subsite; 2. type of intervention; 3. number of study arms; 4. duration of accrual; 5. number of participating centers; 6. number of patients randomized; 7. age and performance status of patients. Outcome measures were age and performance status and average number of patients entered per participating center per year. Publications on nasopharynx cancer were analyzed separately from other HNC. Results The search identified 16,927 publications of which 109 complied with all inclusion criteria comprising 95 clinical trials (14 duplicate publications). Half of the trials included all major head and neck sites and one- third was exclusively for nasopharynx cancers. The experimental intervention was systemic treatment in 54% of the studies and radiotherapy in 26%. Numbers of centers participating in a trial varied from 1 to 367. Median number of patients included was 332 (range 100-1113). Median duration of accrual was 5.4 and 3.8 years for HNC and nasopharynx trials. Median accrual per center per year for HNC and nasopharynx trials was 5.4 and 39.7 patients (table). Mean age of patients randomized was 56 years for HNC and 46 for nasopharynx studies. Mean age of HNC patients in US and Dutch population data bases is 66 years. Of patients in HNC and nasopharynx trials 68% and 80% had a WHO performance score of 0, respectively. Conclusion HNC patients in randomized phase III trials are 10 years younger than the population in daily practice and have a very good performance status. In more than half of the HNC trials the yearly accrual per center was less than 6 patients, suggesting overly restrictive and selective recruitment at some centers. Randomized trials in nasopharynx carcinoma mostly performed in South-East Asia, have faster and less selective accrual. Critical