In the phase III NRG Oncology/RTOG 0232 trial reported in the Journal of Clinical Oncology, Jeff M. Michalski, MD, MBA, FASTRO, and colleagues found no significant benefit in 5-year freedom from disease progression with the addition of external-beam radiation therapy (EBRT) to brachytherapy in patients with intermediate-risk prostate cancer.
In the U.S. multicenter trial, 579 patients were randomly assigned between June 2003 and February 2012 to receive COMBO treatment—with EBRT at 45 Gy in 25 fractions to the prostate and seminal vesicles followed by a brachytherapy prostate boost at 110 Gy if iodine-125 was used or 100 Gy if 103-Pd was used (n = 287)—or brachytherapy alone at 145 Gy if iodine-125 was used or 125 Gy if 103-Pd was used, delivered only to the prostate (n = 292). Patients had to have cT1c-T2bN0M0 disease, a Gleason score of 2 to 6, and prostate-specific antigen (PSA) of 10 to 20 ng/mL, or a Gleason score of 7 and PSA < 10 ng/mL. The primary endpoint was freedom from disease progression, with events defined as PSA failure, using the American Society for Radiation Oncology (ASTRO) or Phoenix definitions, local failure, distant failure, or any-cause death.
Jeff M. Michalski, MD, MBA, FASTRO
Freedom from disease progression at 5 years using the ASTRO definition for PSA failure was 85.6% (95% confidence interval [CI] = 81.4%–89.7%) in the COMBO group vs 82.7% (95% CI = 78.3%–87.1%) in the brachytherapy group (odds ratio [OR] = 0.80, 95% CI = 0.51–1.26, P = .18). The 5-year rate using the Phoenix definition was 88.0% (95% CI = 84.2%–91.9%) in the COMBO group vs 85.5% (95% CI = 81.3%–89.6%) in the brachytherapy group (OR = 0.80, 95% CI = 0.49–1.30, P = .19).
No significant differences in rates of genitourinary or gastrointestinal acute toxicities were observed between groups. The 5-year cumulative incidence of late genitourinary/gastrointestinal grade ≥ 2 toxicity was 42.8% (95% CI = 37.0%–48.6%) in the COMBO group vs 25.8% (95% CI = 20.9%–31.0%) in the brachytherapy group (P < .0001). The 5-year cumulative incidence for late genitourinary/gastrointestinal grade ≥ 3 toxicity was 8.2% (95% CI = 5.4%–11.8%) in the COMBO group vs 3.8% (95% CI = 2.0%–6.5%) in the brachytherapy group (P = .006).
The investigators concluded, “Compared with brachytherapy, COMBO did not improve freedom from progression for prostate cancer but caused greater toxicity. Brachytherapy alone can be considered as a standard treatment for men with intermediate-risk prostate cancer.”
Dr. Michalski, of the Department of Radiation Oncology, Washington University School of Medicine, St. Louis, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by grants from the National Cancer Institute. For full disclosures of the study authors, visit ascopubs.org.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.