Androgen deprivation therapy plus high-dose external beam radiotherapy for oligometastatic prostate cancer with fewer than five regional and/or distant metastases

Abstract

Background: Patients with oligometastatic prostate cancer may experience substantial survival. A metastasis-directed strategy combining androgen deprivation (AD) with high-dose external beam radiotherapy (RT) to isolated regional or distant lesions may be offered to these patients; outcomes of this approach are reported here. Material and methods: From 2003 to 2010, 50 patients with prostate cancer were diagnosed with synchronous (n = 7) or metachronous (n = 43) oligometastases (OM). Among patients with relapse, recurrence occurred after radical prostatectomy in 33 patients and after curative RT, with or without AD, in 10 patients. Median age at diagnosis was 63 years (range, 48-82). At diagnosis or relapse, all patients underwent bone scan and 18F-choline or 11C-acetate PET-CT, showing regional and/or distant nodal metastases in 33 patients and bone and/or visceral metastases in 17 patients. The median delivered effective dose was 64 Gy. All but one patient received neoadjuvant and concomitant AD. Results: After a median follow-up of 31 months (range, 9-89), the 3-year biochemical relapse-free survival (bRFS), clinical failure-free survival, and overall survival rates were 54.5%, 58.6%, and 92%, respectively. No grade 3 toxicity was observed. Improved bRFS was significantly associated with the number of OM: 3-year bRFS was 66.5% for patients with 1 OM versus 36.4% for patients with >1 OM (p = 0.031). A normalised total dose (NTD; 2 Gy/fraction, alpha/beta = 2 Gy) above 64 Gy was also correlated with better 3-year bRFS than lower doses: 65% versus 41.8%, respectively (p = 0.005). On multivariate analysis, only NTD >64 Gy retained statistical significance (HR 0.37, 95% CI 0.15-0.93). Conclusion: Patients with oligometastatic prostate cancer may be successfully treated with short-course AD and high-dose irradiation to metastatic lesions. Higher dose improves bRFS. This strategy may hypothetically prolong the failure-free interval between consecutive AD courses.