The effect of dose‐escalation radiotherapy with simultaneous‐integrated‐boost on the use of short‐term androgen deprivation therapy in patients with intermediate risk prostate cancer

Abstract Purpose To compare the biochemical failure (FFBF) and prostate cancer specific survival (PCSS) rates of patients with intermediate‐risk prostate cancer (IR‐PC) who were treated with 6 months of androgen deprivation therapy (ADT) with 78 Gy to the prostate, those treated with ADT and focal boost (FB) of 86 Gy to intraprostatic lesion (IPL) using the simultaneous‐integrated boost (SIB) technique, and those treated with SIB alone. Materials and Methods A retrospective analysis of 320 IR‐PC patients treated between January 2012 and April 2021 was performed. Patients were divided into three groups based on their treatment arm: 78 + ADT (109 patients, 34.1%), 78/86 (102 patients, 31.8%), and 78/86 + ADT. Univariable and multivariable analyses were used to determine prognostic factors for FFBF and PCSS. Results Median follow‐up was 8.8 years. The 8‐year FFBF and PCSS rates were 88.6% and 99.0%. Patients who received ADT had significantly higher pretreatment PSA levels and clinical tumor stage. Disease progression occurred in 45 patients (7.3%) at a median of 41.9 months after definitive radiotherapy (RT). Younger age, positive core biopsy (PCB) ≥ 50%, and the absence of ADT were all independent predictors of poor FFBF in multivariate analysis, whereas patients with PCB < 50% who were also given ADT had better PCSS. Patients treated with 78/86 Gy alone had worse FFBF than those treated with 78 Gy and ADT (Hazard ratio HR = 3.39 95% CI = 1.46–7.88; p = 0.005), as well as than those treated with 78/86 Gy and ADT (HR = 3.21 95% CI = 1.23–6.46; p = 0.009). However, FB to IPL has no effect on PCSS in multivariable analysis. There was no significant difference between treatment groups in terms of acute and late Grade ≥2 genitourinary or gastrointestinal toxicity. Conclusions Our findings demonstrated that patients who received 78/86 alone did worse than patients who received ADT with either 78 or 78/86 Gy. However, because IR‐PC patients are so diverse, additional prospective trials are needed to validate our findings.