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The aim of this study was to evaluate the outcomes and toxicities of local re-irradiation with stereotactic body radiation therapy (SBRT) in patients with local recurrence of prostate cancer after curative radiotherapy.

Twenty patients were treated with SBRT between December 2010 and March 2020. All patients had clinical/radiological local relapse in the prostate and no distant metastasis. Fourteen patients (70%) received 30 Gy in 5 fractions/3w, 3 (15%) received 25 Gy in 5 fractions/3w, 2 (10%) received 23 Gy in single fraction and 1 (5%) 37.5 Gy in 5 fractions/3w. All patients underwent image-guided radiotherapy (IGRT) using cone-beam computed tomography (CBCT) system as daily pre-treatment imaging. Seven out of 20 patients (35%) received also hormonal deprivation therapy. Toxicity was evaluated using the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer Criteria. Biochemical control was assessed according to the Phoenix definition (NADIR + 2 ng ml (-1)).

Median follow-up was 36 months (range 2-85 months). Median age was 78 years (range 65-89 years), median pre-SBRT prostate specific antigen (PSA) was 3.3 ng ml (range 0.24-18.3 ng/ml). The median planning target volume (PTV) was 65 cm3 (range 8-148.7 cm3). The median overall survival (OS) was 57 months (95% i.c. 23.5-90.8) and the actuarial 2-year and 5-year OS was 89% and 40% respectively. Two-year and 5-year Biochemical free survival (BFS) was 55% and 47%, respectively. Local control (LC) at 2-year and 5-year was 73% and 62%, respectively. Disease free survival (DFS) at 2-year and 5-year was 67% and 57%, respectively. Median BFS, LC and DFS were not reached. Six patients (30%) experienced grade 1-2 acute urinary toxicities. Grade 1-2 late urinary toxicities were reported in 13 patients (65%).

SBRT re-irradiation for locally recurrent prostate cancer offers a satisfactory tumor control and shows a low toxicity profile.