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The aim of this mono-institutional retrospective 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.

Thirty patients were enrolled in this study. All patients presented clinical and radiological local relapse in the prostate and no distant metastasis diagnosed with multi-parametric magnetic resonance and Choline PET-TC. All of them were treated with SBRT between December 2010 and May 2022. Twenty four patients (80%) received 30 Gy in 5 fractions/3w, 3 (10%) received 25 Gy in 5 fractions/3w, 2 (7%) received 23 Gy in single fraction and 1 (3%) received 27.5 Gy in five fractions/3w. All patients underwent image-guided radiotherapy (IGRT) using cone-beam computed tomography (CBCT) system as daily pre-treatment imaging. Twelve out of 30 patients (40%) 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 actuarial follow-up was 36.7 months (95% CI 21.07-52.32, range 1.6 – 85.3). Median age was 78 years (range 66-89 years), median pre-SBRT prostate specific antigen (PSA) was 3.79 ng ml (range 0.05-20 ng/ml). The median planning target volume (PTV) was 63 cm3 (range 9-149 cm3). Five and 10-year overall survival (OS) from primary diagnosis were 96.7% and 83.2%, respectively. Median, 1 and 3-year OS from re-irradiation were 63.7 months (95% IC 54.27-73.12), 96.7% and 80.7%, respectively. One and 3-year biochemical free survival (BFS) were 82.1% and 43.7%, respectively. One and 3-year local control (LC) were 92.3% and 58.1%, respectively. One and 3-year disease free survival (DFS) were 85.7% and 44.9%, respectively. One and 3-year metastasis free survival (MFS) were 96.2% and 73.6%, respectively. Median LC and MFS were not reached.  Eight patients (27%) experienced grade 1-2 acute urinary toxicities . Grade 1-2 late urinary toxicities were reported in 10 patients (33%). Three patients (10%) experienced grade 1-2 acute gastrointestinal toxicities . Three patients (10%) experienced grade 1-2 late gastrointestinal toxicities.

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