Linac-based SBRT as a feasible salvage option for local recurrences in previously irradiated prostate cancer

The optimal management of prostate cancer (PC) recurrences after definitive or postoperative radiotherapy (RT) is still controversial. The aim of the present retrospective study was to report the preliminary clinical results and toxicity of a mono-institutional series of patients re-irradiated with linac-based SBRT in recurrent prostate cancer. Inclusion criteria were previous definitive or adjuvant/salvage RT, evidence of biochemical recurrence and radiological detection of local relapse (Magnetic Resonance Imaging or PSMA/choline-Positron Emission Tomography), and IPSS <10. Toxicity was assessed according to Common Terminology Criteria for Adverse Events v4.0. Between 12/2014 and 12/2019, 24 patients with median age 75 years (65–89) underwent re-RT for PC recurrence. Median follow-up was 21 months (2–68). The recurrences occurred in 13 cases within the prostate and in 11 cases within the prostate bed. All patients were treated with SBRT to a median total dose of 30 Gy (25–36 Gy) in 5–6 fractions, and simultaneous androgen deprivation therapy was administered in 4 patients. Acute toxicity was G1 in 8.3% and G2 in 12.5% for genitourinary (GU), no acute gastrointestinal (GI) toxicity occurred. Concerning late side effects, 19.7% of patients were found to have ≥G2 GU toxicity, including one G3 urethral stenosis. Only one case of G1 late GI toxicity occurred and no ≥G2. The 2‑year overall survival was 95%. The 1‑ and 2‑year biochemical relapse-free survival (BRFS) and progression-free survival (PFS) rates were 80 and 54.9%, respectively. Despite of the heterogeneity of the sample, linac-based SBRT as a salvage treatment in previously irradiated locally recurrent PC patients seems to be a safe and feasible treatment option. Long-term data are pending.