Adherence to contouring and treatment planning requirements within a multicentric trial -results of the quality assurance of the SAKK 09/10 trial.

To evaluate the results of the radiation therapy (RT) quality assurance (QA) program of the phase III randomized "XXXX-Anonymized for Review" trial in biochemically recurrent prostate cancer (PC) patients after prostatectomy.

Within the "XXXX-Anonymized for Review" trial testing 64Gy versus 70Gy salvage RT, a central collection of treatment plans were performed, which were thoroughly reviewed by a dedicated medical physicist and radiation oncologist. Adherence to the treatment protocol and specifically to the European Organization for the Research and Treatment of Cancer (EORTC) guidelines for target volume definition (classified as deviation observed yes vs. no) and its potential correlation with acute and late toxicity (Common Terminology Criteria for Adverse Events (CTCAE) v4.0) and freedom from biochemical progression (FFBP) were investigated.

The treatment plans of 344 patients treated between February 2011 and April 2014 depicted important deviations to the EORTC guidelines and to the recommendations per trial protocol. For example, in up to half of the cases, the delineated structures deviated from the protocol (e.g., prostate bed (PB) in 48.8%, rectal wall (RW) in 41%). In addition, variations in clinical (CTV) - and planning target volume (PTV) occurred frequently (e.g., CTV and PTV deviations in up to 42.4% and 25.9%, respectively). The detected deviations showed a significant association with a lower risk of grade ≥ 2 gastrointestinal (GI) acute toxicity when CTV not overlapped RW vs. CTV overlapping RW, (OR 0.43; CI [0.22, 0.85]; p= 0.014), and a higher rate of grade ≥ 2 late genitourinary (GU) toxicity in case of the CTV overlapped with RW, (OR 2.58; CI [1.17, 5.72]; p= 0.019). A marginally significant lower risk of grade ≥ 2 late GU toxicity in patients when PB not overlapping RW versus overlapping RW was observed (OR 0.51; CI [0.25, 1.03]; p= 0.06). In addition, a marginally significant decrease of FFBP in patients with PTV not including surgical clips as potential markers of the limits of the prostate bed, (HR 1.44; CI [0.96, 2.17]; p= 0.07) was observed.

Despite a thorough QA program, the central review of a phase-III trial showed limited adherence to treatment protocol recommendations which was associated with a higher risk of toxicity by means of acute or late GI or GU toxicity and showed a trend towards worse FFBP. Data from this QA review may help refine future QA programs and prostate bed delineation guidelines.

International journal of radiation oncology, biology, physics. 2022 Jan 03 [Epub ahead of print]

Marcus Beck, Manfred Sassowsky, Sämi Schär, EtienneMatthias MathierHalter, Daniel R Zwahlen, Tobias Hölscher, Winfried Arnold, Bülent Polat, Guido Hildebrandt, Arndt-Christian Müller, Paul M Putora, Alexandros Papachristofilou, Stefanie Hayoz, Corinne Schär, Qiyu Li, Marcin Sumila, Kathrin Zaugg, Matthias Guckenberger, Piet Ost, Davide G Bosetti, Christiane Reuter, Silvia Gomez, Kaouthar Khanfir, Daniel M Aebersold, Pirus Ghadjar, Alan Dal Pra, Swiss Group for Clinical Cancer Research (SAKK)

Department of Radiation Oncology, Charité Universitätsmedizin Berlin, Germany. Electronic address: ., Department of Radiation Oncology, Inselspital, Bern University Hospital and University of Bern, Switzerland., SAKK Coordinating Center, Bern, Switzerland., University Hospital Tübingen, Germany., Department of Radiation Oncology, Kantonsspital Graubünden, Chur, Switzerland now at Kantonsspital Winterthur, Switzerland., Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Germany., Department of Radiation Oncology, Kantonsspital Luzern, Switzerland., Department of Radiation Oncology, University of Würzburg, Germany., Department of Radiation Oncology, University Hospital Rostock, Germany., Department of Radiation Oncology, Inselspital, Bern University Hospital and University of Bern, Switzerland; Department of Radiation Oncology, Kantonsspital St. Gallen, Switzerland., Department of Radiation Oncology, University Hospital Basel, Switzerland., SAKK Coordinating Center, Bern, Switzerland. Electronic address: ., Department of Radiation Oncology, Hirslanden Hospital Group, Zürich, Switzerland., Department of Radiation Oncology, Inselspital, Bern University Hospital and University of Bern, Switzerland; Department of Radiation Oncology, Stadtspital Triemli, Zürich, Switzerland., Department of Radiation Oncology, University Hospital Zürich, Switzerland., Department of Radiation Oncology, Ghent University Hospital, Belgium., Istituto Oncologico della Svizzera Italiana, Bellinzona, Switzerland., Department of Radiation Oncology, Kantonsspital Münsterlingen, Switzerland., RadiationOncologyCenter KSA-KSB, Aarau, Switzerland., Department of Radiation Oncology, Hôpital Valais, Sion, Switzerland., Department of Radiation Oncology, Charité Universitätsmedizin Berlin, Germany; Department of Radiation Oncology, Inselspital, Bern University Hospital and University of Bern, Switzerland., Department of Radiation Oncology, Inselspital, Bern University Hospital and University of Bern, Switzerland; Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, FL, USA.

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