Dose escalation for prostate stereotactic ablative radiotherapy (SABR): Late outcomes from two prospective clinical trials

Publication date: Available online 24 March 2018
Source:Radiotherapy and Oncology
Author(s): Yasir Alayed, Patrick Cheung, Geordi Pang, Alexandre Mamedov, Laura D'Alimonte, Andrea Deabreu, Kristina Commisso, Angela Commisso, Liang Zhang, Harvey C. Quon, Hima Bindu Musunuru, Joelle Helou, D. Andrew Loblaw
PurposeOptimal prostate SABR dose-fractionation is unknown. This study compares long-term outcomes from two prospective trials.MethodsStudy1 patients had low-risk PCa and received 35 Gy/5. Study2 patients had low/intermediate-risk PCa and received 40 Gy/5. Biochemical failure (BF) was defined as nadir + 2.Results114 patients were included (study1, n = 84; study2, n = 30). Median follow-up was 9.6 years and 6.9 years. Median nPSA was 0.4 and 0.1 ng/ml. Nine patients had BF (8 in study1, 1 in study2); two were managed with ADT and four had local salvage. The BF rate was 2.5% and 12.8% at 5 and 10 years for study1 and 3.3% at 5 years for study 2. BF probability was 0% if PSA <0.4 at 4 years, and 20.5% at 10 years if PSA ≥0.4 (p = 0.02). Nine patients died, none of PCa. No patient has metastases or castrate-resistance. At 10 years, OS and CSS were 90.4% (p = 0.25) and 100%.ConclusionsDose-escalated prostate SABR was associated with lower nPSAs but no difference in BF, OS, CSS or MFS. PSA <0.4 at 4 years was a predictor of biochemical control. Half of patients with BF were successfully salvaged. Given that this is a favorable-risk cohort, longer follow-up will be needed to see if the lower nPSA translates into lower BF rates.



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