Salvage stereotactic body radiotherapy for local prostate cancer recurrence after radiotherapy: a retrospective multicentre study of the GETUG

BACKGROUND: and purpose: To assess the efficacy and safety of salvage stereotactic body radiotherapy (SBRT) in patients with biopsy-proven local prostate cancer recurrence after radiotherapy. METHODS AND MATERIALS: Between April 2010 and January 2017, 100 patients were included in 7 centers. Disease extension was assessed by pelvic multiparametric magnetic resonance imaging and choline positron emission tomography in 87% and 94% of patients, respectively. The median time interval between the two treatments was 7.5 years (range, 2-18). Median PSA at recurrence was 4.3 ng/mL (range, 2-38). Median SBRT dose was 36 Gy (range, 25-36.25) in 6 fractions (range, 5-6), every other day. Thirty-four percent of patients were treated by androgen deprivation therapy for a median duration of 12 months. Toxicity was assessed according to CTCAE v.4.03. RESULTS: Median follow-up was 29.3 months (range, 4-91). Second biochemical recurrence-free survival rate at 3 years was 55% [95% CI: 42%-66%]. The initial D'Amico group, time interval after first radiotherapy and SBRT dose were prognostic factors of biochemical recurrence-free survival in multivariate analysis (p=0.09, p=0.025, p=0.018, respectively). No patient developed acute gastro-intestinal (GI) toxicity of grade > 1; acute genito-urinary (GU) toxicity of grade 2 and 3 were 8% and 1%, respectively. The actuarial 3-year grade ≥2 GU and GI toxicity was 20.8% (95% CI: 13%-29%) and 1% (95% CI: 0.1%-5.1%), respectively. One patient presented a neuritis of grade 3. CONCLUSION: With a short follow up, this study shows that salvage SBRT allows for encouraging control and acceptable toxicity. Further prospective studies are necessary to confirm these preliminary results and to determine late toxicity.