Disease Control Outcomes of Stereotactic Body Radiation Therapy or Moderate Hypo - Fractionation for Prostate Cancer: Real - World Experience at Two Canadian Centers.

Introduction: Advantages of using stereotactic body radiation therapy to treat prostate cancer include short treatment times, decreased costs, and limited toxicity. Randomized trial outcomes comparing 5 - fraction stereotactic body radiation therapy to conventionally fractionated radiotherapy or hypo - fractionated radiation therapy are pending. Methods: Patients with low - or intermediate - risk prostate cancer treated with stereotactic body radiation therapy alone (35 - 40 Gy in 5 fractions) or hypo - fractionated radiation therapy alone (60 - 62 Gy in 20 fractions) in the period of July 2010 and June 2020. The biochemical relapse - free survival, PSA nadir, interval time to PSA nadir, time to biochemical recurrence (2 ng/ml above PSA nadir) and overall survival were reviewed. Outcomes between treatment groups were compared after propensity - matching by patient baseline characteristics. Kaplan - Meier curves were used to assess biochemical relapse - free survival and overall survival. Results: We identified 205 and 513 patients with low or intermediate - risk prostate cancer who were treated with stereotactic body radiation therapy or hypo - fractionation, respectively. Intermediate - risk category composed 81% and 95% of the stereotactic body radiation therapy and hypo - fractionated radiation therapy cohorts, respectively. After a median follow up of 58.6 months for the stereotactic body radiation therapy cohort and 45.0 months for the hypo - fractionated cohort, biochemical relapse - free survival and overall survival were not significantly different between treatment groups. The 5 - year biochemical relapse - free survival rates were 92.1% and 93.6% and overall survival rates were 96.4% and 95.0% for the stereotactic body radiation therapy and hypo - fractionated cohorts, respectively, after propensity - matching. Stereotactic body radiation therapy resulted in a significantly lower PSA nadir (0.18 ng/ml) compared to hypo - fractionated radiation therapy (0.48 ng/ml) in patients with low - risk prostate cancer. Mean time to biochemical recurrence was not different between treatment groups. Conclusions: Stereotactic body radiation therapy is an effective treatment option for low and intermediate - risk prostate cancer with encouraging biochemical relapse - free survival and overall survival rates comparable with hypo - fractionated radiation therapy. [ABSTRACT FROM AUTHOR]