A single-center study of 100 consecutive patients with localized prostate cancer treated with stereotactic body radiotherapy

BACKGROUND Radiotherapy is an increasingly preferred treatment option for localized prostate cancer, and stereotactic body radiation therapy (SBRT) a relatively established modality of therapeutic irradiation. The present study analyzes the toxicity and biochemical efficacy of SBRT in 100 consecutive prostate cancer patients treated with CyberKnife Robotic Radiosurgery System. METHODS One hundred patients were treated with SBRT at the Radiation Oncology department of San Bortolo Hospital, Vicenza, Italy. All patients included in this IRB-approved protocol-driven prospective study had biopsy-proven prostate cancer. Risk category was low in 41, intermediate in 42, and high in 17 patients. The patients were treated with CyberKnife-SBRT (CK-SBRT), the prescription dose was 35 Gy in five fractions, corresponding to 92 Gy in 2-Gy fractions (α/β =1.5 Gy); 29 patients also received androgen deprivation therapy (ADT). RESULTS Median follow-up was 36 months (range, 6-76 months). Acute Grade 2 genitourinary and gastrointestinal toxicity occurred in respectively 12% and 18% of the patients; there were no Grade 3 or higher acute toxicities. Late Grade 1, 2, and 3 genitourinary toxicities occurred in 4%, 3%, and 1% of the patients, respectively; late Grade 1 gastrointestinal toxicity occurred in two patients and Grade 2 toxicity in one patient; no late gastrointestinal toxicities of grade 3 or 4 were observed. Median PSA nadir was 0.45 ng/ml at 36 months for all patients. In the SBRT-monotherapy group, the median PSA nadir at 36 months was 0.62 ng/ml; in the ADT-SBRT group, it was 0.18 ng/ml. Four patients had clinical recurrence: one local, two lymph nodes, and one to the bone. Ninety-six patients had no evidence of biochemical or clinical recurrence. A benign PSA bounce of median 1.08 ng/ml occurred in 12% of the 71 SBRT monotherapy patients at a mean 23 months (range, 18-30 months). CONCLUSIONS In this study CK-SBRT has provided promising outcomes in localized prostate cancer with good PSA response, minimal toxicity and patient inconvenience.