Retrospective Analysis of Clinical Outcomes of Stereotactic Body Radiation Therapy for Localized Prostate Cancer at an Asian Cancer Specialist Centre

INTRODUCTION: The current treatment options for localized prostate cancer are radical prostatectomy and external beam radiotherapy (EBRT) with stereotactic body radiation therapy (SBRT) gaining interest as a treatment option compared to standard fractionation radiation therapy. This present study is a retrospective study evaluating the correlations between the biochemical efficacy, and treatment toxicity in SBRT for localized prostate cancer. METHODS: All organ-confined prostate cancer patients treated with SBRT from 2010 to 2018, at Beacon Hospital, Malaysia were included in this study. Patient demographics, dosimetric parameters, and disease information were retrospectively collected. The primary endpoint was biochemical recurrence-free survival assessed using the Phoenix definition (Nadir + 2 ng/mL). Toxicity outcomes were scored using the Radiation Therapy Oncology Group scale. RESULTS: Fourty-nine patients who met the inclusion criteria (5 low-, 13 intermediate- and 31 high-risk according to the D’amico Risk Classification) received SBRT. The most common dose regime was 34-35Gy in 5 fractions (n=18). Other dose regimes were 24Gy in 3 fractions and 25-33Gy in 5 fractions. Median follow-up was 45.4 months. The median pre-treatment prostate-specific antigen (PSA) was 11.22 ng/mL, which decreased to a median PSA of 0.1 ng/mL by 2 years post-treatment. Out of the 49 cases, only 1 case of biochemical recurrence occurred, yielding a 3- and 5-year overall survival of 100%, and a 3- and 5- year biochemical recurrence-free rate of 100% and 95.2%. Acute grade III urinary toxicities occurred in 1 (2%); whereas acute grade I urinary and rectal toxicities were seen in 22 (44.9%) and 7 (14.3%) patients respectively. Grade I and grade III late rectal toxicities occurred in 3 and 1 patients respectively, while 3 and 1 patient reported late grade I and III urethral stricture respectively. CONCLUSION: SBRT for clinically-localized and locally advanced prostate cancer provided promising outcomes with low toxicity and good biochemical control.