Maud Jaccard1, Thomas Zilli2, Angèle Dubouloz3, Lluís Escude4, Sandra Jorcano4, Nadine Linthout5, Samuel Bral5, Wilko Verbakel6, Anna Bruynzeel6, Mikko Björkqvist7, Heikki Minn8, Lev Tsvang9, Zvi Symon9, Joana Lencart10, Angelo Oliveira11, Zeynep Ozen12, Ufuk Abacioglu12, Juan María Pérez-Moreno13, Carmen Rubio13, Michel Rouzaud3, Raymond Miralbell14. 1. Radiation Oncology, University Hospital of Geneva, Geneva, Switzerland. Electronic address: maud.jaccard@hcuge.ch. 2. Radiation Oncology, University Hospital of Geneva, Geneva, Switzerland; Faculty of Medicine, Geneva University, Geneva, Switzerland. 3. Radiation Oncology, University Hospital of Geneva, Geneva, Switzerland. 4. Radiation Oncology, Teknon Oncologic Institute, Barcelona, Spain. 5. Onze-Lieve-Vrouwziekenhuis, Aalst, Belgium. 6. Radiation Oncology Amsterdam UMC, Amsterdam, the Netherlands. 7. Department of Oncology and Radiotherapy, Turku University Hospital, Turku, Finland; Department of Medical Physics, Division of Medical Imaging, Turku University Hospital, Turku, Finland. 8. Department of Oncology and Radiotherapy, Turku University Hospital, Turku, Finland. 9. Sheba Medical Center, Ramat Gan, Israel. 10. Faculty of Medicine, Geneva University, Geneva, Switzerland. 11. Portuguese Institut of Oncology, Porto, Portugal. 12. Neolife Medical Center, Istanbul, Turkey. 13. Hospital Universitario Sanchinarro, Madrid, Spain. 14. Radiation Oncology, University Hospital of Geneva, Geneva, Switzerland; Faculty of Medicine, Geneva University, Geneva, Switzerland; Radiation Oncology, Teknon Oncologic Institute, Barcelona, Spain.
Abstract
PURPOSE: To present the radiation therapy quality assurance results from a prospective multicenter phase 2 randomized trial of short versus protracted urethra-sparing stereotactic body radiation therapy (SBRT) for localized prostate cancer. METHODS AND MATERIALS: Between 2012 and 2015, 165 patients with prostate cancer from 9 centers were randomized and treated with SBRT delivered either every other day (arm A, n = 82) or once a week (arm B, n = 83); 36.25 Gy in 5 fractions were prescribed to the prostate with (n = 92) or without (n = 73) inclusion of the seminal vesicles (SV), and the urethra planning-risk volume received 32.5 Gy. Patients were treated either with volumetric modulated arc therapy (VMAT; n = 112) or with intensity modulated radiation therapy (IMRT; n = 53). Deviations from protocol dose constraints, planning target volume (PTV) homogeneity index, PTV Dice similarity coefficient, and number of monitor units for each treatment plan were retrospectively analyzed. Dosimetric results of VMAT versus IMRT and treatment plans with versus without inclusion of SV were compared. RESULTS: At least 1 major protocol deviation occurred in 51 patients (31%), whereas none was observed in 41. Protocol violations were more frequent in the IMRT group (P < .001). Furthermore, the use of VMAT yielded better dosimetric results than IMRT for urethra planning-risk volume D98% (31.1 vs 30.8 Gy, P < .0001), PTV D2% (37.9 vs 38.7 Gy, P < .0001), homogeneity index (0.09 vs 0.10, P < .0001), Dice similarity coefficient (0.83 vs 0.80, P < .0001), and bladder wall V50% (24.5% vs 33.5%, P = .0001). To achieve its goals volumetric modulated arc therapy required fewer monitor units than IMRT (2275 vs 3378, P <.0001). The inclusion of SV in the PTV negatively affected the rectal wall V90% (9.1% vs 10.4%, P = .0003) and V80% (13.2% vs 15.7%, P = .0003). CONCLUSIONS: Protocol deviations with potential impact on tumor control or toxicity occurred in 31% of patients in this prospective clinical trial. Protocol deviations were more frequent with IMRT. Prospective radiation therapy quality assurance protocols should be strongly recommended for SBRT trials to minimize potential protocol deviations.
RCT Entities:
PURPOSE: To present the radiation therapy quality assurance results from a prospective multicenter phase 2 randomized trial of short versus protracted urethra-sparing stereotactic body radiation therapy (SBRT) for localized prostate cancer. METHODS AND MATERIALS: Between 2012 and 2015, 165 patients with prostate cancer from 9 centers were randomized and treated with SBRT delivered either every other day (arm A, n = 82) or once a week (arm B, n = 83); 36.25 Gy in 5 fractions were prescribed to the prostate with (n = 92) or without (n = 73) inclusion of the seminal vesicles (SV), and the urethra planning-risk volume received 32.5 Gy. Patients were treated either with volumetric modulated arc therapy (VMAT; n = 112) or with intensity modulated radiation therapy (IMRT; n = 53). Deviations from protocol dose constraints, planning target volume (PTV) homogeneity index, PTV Dice similarity coefficient, and number of monitor units for each treatment plan were retrospectively analyzed. Dosimetric results of VMAT versus IMRT and treatment plans with versus without inclusion of SV were compared. RESULTS: At least 1 major protocol deviation occurred in 51 patients (31%), whereas none was observed in 41. Protocol violations were more frequent in the IMRT group (P < .001). Furthermore, the use of VMAT yielded better dosimetric results than IMRT for urethra planning-risk volume D98% (31.1 vs 30.8 Gy, P < .0001), PTV D2% (37.9 vs 38.7 Gy, P < .0001), homogeneity index (0.09 vs 0.10, P < .0001), Dice similarity coefficient (0.83 vs 0.80, P < .0001), and bladder wall V50% (24.5% vs 33.5%, P = .0001). To achieve its goals volumetric modulated arc therapy required fewer monitor units than IMRT (2275 vs 3378, P <.0001). The inclusion of SV in the PTV negatively affected the rectal wall V90% (9.1% vs 10.4%, P = .0003) and V80% (13.2% vs 15.7%, P = .0003). CONCLUSIONS: Protocol deviations with potential impact on tumor control or toxicity occurred in 31% of patients in this prospective clinical trial. Protocol deviations were more frequent with IMRT. Prospective radiation therapy quality assurance protocols should be strongly recommended for SBRT trials to minimize potential protocol deviations.