To perform a propensity-score matched analysis comparing SBRT boost and HDR boost for localized prostate cancer.
A single-institution retrospective chart review was conducted of men treated with pelvic external beam radiotherapy (EBRT) and SBRT boost (21Gy/19Gy in 2 fractions) to the prostate for prostate cancer.
A cohort treated at the same institution with high-dose rate (HDR) brachytherapy boost (19Gy in 2 fractions) was compared. Propensity-score (PS) matching and multivariable Cox regression were used for analysis. Outcomes were biochemical-recurrence-freedom (BCRF) and metastasis-freedom (MF).
131 men were treated with SBRT boost and 101 with HDR boost with median follow-up of 73.4 and 186.0 months, respectively. 68.8% of men had high-risk and 26.0% had unfavorable-intermediate disease, and 94.3% received androgen deprivation therapy (ADT). Five- and 10-year unadjusted BCRF was 88.8%/85.3% for SBRT and 91.8%/74.6% for HDR boost (Log-Rank P=0.3), and 5- and 10-year unadjusted MF was 91.7%/84.3% for SBRT and 95.8%/82.0% for HDR (Log-Rank P=0.8). After adjusting for covariates, there was no statistically significant difference in BCRF (HR 0.81, 95% confidence interval [CI] 0.37-1.79, P=0.6) or MF (HR 1.07, 95% CI 0.44-2.57, P=0.9) between SBRT and HDR boost. Similarly, after PS matching, there was no statistically significant difference between SBRT and HDR (BCRF: HR 0.66, 0.27-1.62, P=0.4; MF: HR 0.84, 0.31-2.26, P=0.7). Grade 3+ genitourinary and gastrointestinal toxicity in the SBRT cohort were 4.6% and 1.5%, and 3.0% and 0.0% in the HDR cohorts (P=0.4, Fisher test).
SBRT boost plus pelvic EBRT for prostate cancer resulted in similar BCRF and MF to HDR boost in this single institution, PS matched retrospective analysis. Toxicity was modest. Prospective evaluation of SBRT boost for the treatment of unfavorable-intermediate and high-risk prostate cancer is warranted.
International journal of radiation oncology, biology, physics. 2020 Dec 29 [Epub ahead of print]
William C Chen, Yun Li, Ann Lazar, Aysu Altan, Martina Descovich, Tomi Nano, Benjamin Ziemer, Atchar Sudhyadhom, Adam Cunha, Horatio Thomas, Alexander Gottschalk, I-Chow Hsu, Mack Roach
Department of Radiation Oncology, University of California San Francisco, California 94143., Division of Oral Epidemiology and Dental Public Health, University of California San Francisco, California 94143; Division of Biostatistics, University of California San Francisco, California 94143., Department of Radiation Oncology, University of California San Francisco, California 94143. Electronic address: .