Can we avoid dose escalation for intermediate-risk prostate cancer in the setting of short-course neoadjuvant androgen deprivation?

Thomas P Shakespeare,1,2 Shea W Wilcox,1 Noel J Aherne1,2 1Department of Radiation Oncology, North Coast Cancer Institute, 2Faculty of Medicine, Rural Clinical School, The University of New South Wales, Coffs Harbour, New South Wales, Australia Background: Both dose-escalated external beam radiotherapy (DE-EBRT) and androgen deprivation therapy (ADT) improve the outcomes in patients with intermediate-risk prostate cancer. Despite this, there are only few reports evaluating DE-EBRT for patients with intermediate-risk prostate cancer receiving neoadjuvant ADT, and virtually no studies investigating dose escalation >74Gy in this setting. We aimed to determine whether DE-EBRT >74Gy improved the outcomes for patients with intermediate-risk prostate cancer who received neoadjuvant ADT. Findings: In our institution, patients with intermediate-risk prostate cancer were treated with neoadjuvant ADT and DE-EBRT, with doses sequentially increasing from 74Gy to 76Gy and then to 78Gy between 2006 and 2012. We identified 435 patients treated with DE-EBRT and ADT, with a median follow-up of 70months. For the 74Gy, 76Gy, and 78Gy groups, five-year biochemical disease-free survival rates were 95.0%, 97.8%, and 95.3%, respectively; metastasis-free survival rates were 99.1%, 100.0%, and 98.6%, respectively; and prostate cancer-specific survival rate was 100% for all three dose levels. There was no significant benefit for dose escalation either on univariate or multivariate analysis for any outcome. Conclusion: There was no benefit for DE-EBRT >74Gy in our cohort of intermediate-risk prostate cancer patients treated with neoadjuvant ADT. Given the higher risks of toxicity associated with dose escalation, it may be feasible to omit dose escalation in this group of patients. Randomized studies evaluating dose de-escalation should be considered. Keywords: radiotherapy, IMRT, dose, dose escalation, dose de-escalation, androgen deprivation therapy, prostate cancer