ESTRO 2021 Abstract Book

S1218

ESTRO 2021

and standardized on training assessment.

Conclusion The majority of residents in Europe, are interested in performing BT after they complete their training, but don’t feel confident they will achieve this goal. To address this gap, efforts are needed to develop and implement a formal and comprehensive BT curriculum with easy access to trained instructors. PO-1488 Patient’s opinion on serving as control in the trials within cohort design – results of a survey M. Verweij 1 , M. Burbach 2 , R. Gal 3 , A. May 3 , R. van der Graaf 4 , M. Intven 1 , L. Verkooijen 1 1 University Medical Center Utrecht, Radiation-Oncology, Utrecht, The Netherlands; 2 University Medical Center Groningen, Surgery, Groningen, The Netherlands; 3 Julius Research Center, Epidemiology, Utrecht, The Netherlands; 4 Julius Research Center, Medical Humanities, Utrecht, The Netherlands Purpose or Objective Trials within cohorts (TwiCs) is an efficient study design for evaluating multiple interventions in an oncology setting. TwiCs embeds pragmatic randomized trials within a cohort study. According to the staged-informed consent procedure for TwiCs, patients are asked for broad consent for future randomization upon cohort enrollment. This includes consent for use of medical data for comparative purposes if randomized to the control group of an embedded trial. If randomized to the intervention group, patients are asked to sign a second trial-specific consent. Patients in the control arm of TwiCs receive care as usual and are not explicitly notified that they take part in a clinical trial. In this study the opinion of patients who had served as control in TwiCs was asked, in order to assess the acceptability of the TwiCs design. Materials and Methods A survey was conducted among patients with rectal or breast cancer who were randomized to the control arms of two TwiCs (resp. the RECTAL-BOOST (RB) and UMBRELLA FIT (UF) trials). The survey questioned patient’s opinion of having served as control before and after providing the respective trial results. RB control patients were informed that a boost prior to chemoradiation did not result in a higher probability of pathological complete response. UF control patients were informed that an exercise program 12-18 months after breast cancer treatment resulted in less complaints of fatigue. Results 37 of 49 (76%) RB and 69 of 69 (72%) UF control patients completed the questionnaire. 54% of RB and 70% of UF did not remember providing broad consent for future randomization at median 4 (range: 2-5) resp. 5 (2-8) years after cohort enrollment. Before providing the trial results, 51% of RB and 45% of UF indicated a positive opinion and 43% resp. 46% a neutral opinion on having served as control in a TwiC. 22% of RB and 13% of UF thought positively and 62% resp. 68% neutrally about not receiving a notification when serving as control. After providing the trial results, 57% of RB and 52% of UF indicated a positive opinion and 43% resp. 39% a neutral opinion on having served as control. 19% of RB and 25% of UF thought positively and 65% resp. 60% neutrally about not receiving a notification when serving as control. A reminder during cohort participation for the broad consent provided would have been appreciated by 70% of RB and 59% of UF patients.