Treatment outcomes of prostate cancer patients with Gleason score 8–10 treated with definitive radiotherapy: TROD 09-001 multi-institutional study [Behandlungsergebnisse von mit definitiver Strahlentherapie behandelten Prostatakrebspatienten mit einem Gleason-Score von 8–10: TROD 09-001 Multizenterstudie]

###EgeUn###Purpose: To validate the clinical outcomes and prognostic factors in prostate cancer (PCa) patients with Gleason score (GS) 8–10 disease treated with external beam radiotherapy (EBRT)?+ androgen deprivation therapy (ADT) in the modern era. Methods: Institutional databases of biopsy proven 641 patients with GS 8–10 PCa treated between 2000 and 2015 were collected from 11 institutions. In this multi-institutional Turkish Radiation Oncology Group study, a standard database sheet was sent to each institution for patient enrollment. The inclusion criteria were, T1–T3N0M0 disease according to AJCC (American Joint Committee on Cancer) 2010 Staging System, no prior diagnosis of malignancy, at least 70?Gy total irradiation dose to prostate?± seminal vesicles delivered with either three-dimensional conformal RT or intensity-modulated RT and patients receiving ADT. Results: The median follow-up time was 5.9 years (range 0.4–18.2 years); 5-year overall survival (OS), biochemical relapse-free survival (BRFS) and distant metastases-free survival (DMFS) rates were 88%, 78%, and 79%, respectively. Higher RT doses (?78?Gy) and longer ADT duration (?2 years) were significant predictors for improved DMFS, whereas advanced stage was a negative prognosticator for DMFS in patients with GS 9–10. Conclusions: Our results validated the fact that oncologic outcomes after radical EBRT significantly differ in men with GS 8 versus those with GS 9–10 prostate cancer. We found that EBRT dose was important predictive factor regardless of ADT period. Patients receiving ‘non-optimal treatment’ (RT doses <78?Gy and ADT period