As reported in the Journal of Clinical Oncology by W. Robert Lee, MD, MS, and colleagues, a 12-year analysis of the phase III NRG Oncology RTOG 0415 trial has shown continued noninferiority in terms of disease-free survival with hypofractionated radiotherapy vs conventionally fractionated radiotherapy in patients with low-risk prostate cancer.
A prior report from the trial—a median follow-up of 5.8 years—showed noninferiority of hypofractionated radiotherapy vs conventionally fractionated radiotherapy.
W. Robert Lee, MD, MS
Study Details
In the noninferiority trial, 1,092 patients were randomly assigned to receive hypofractionated radiotherapy with 70 Gy in 28 fractions (n = 550) or conventionally fractionated radiotherapy with 73.8 Gy in 41 fractions. Radiotherapy was delivered as 3D or intensity-modulated treatment, with the latter used in 79% of patients. Androgen-deprivation therapy was not permitted. The primary endpoint of the trial was disease-free survival.
Key Findings
Median follow-up in the current analysis was 12.8 years. Disease-free survival rates at 12 years were 61.8% (95% confidence interval [CI] = 57.2%–66.0%) in the hypofractionated radiotherapy group vs 56.1% (95% CI = 51.5%–60.5%) in the conventionally fractionated radiotherapy group (hazard ratio [HR] = 0.85, 95% CI = 0.71–1.03), confirming noninferiority of hypofractionated radiotherapy (P < .001 for noninferiority).
The 12-year cumulative incidence of biochemical failure was 9.9% (95% CI = 7.5%–12.6%) in the hypofractionated radiotherapy group vs 17.0% (95% CI = 13.8%–20.5%) in the conventionally fractionated radiotherapy group (HR = 0.55, 95% CI = 0.39–0.78).
Overall survival at 12 years was 69.9% (95% CI = 65.5%-73.9%) in the hypofractionated radiotherapy group vs 68.7% (95% CI = 64.3%–72.7%) in the conventionally fractionated radiotherapy group.
Overall, late grade ≥ 3 gastrointestinal adverse events occurred in 4.4% of the hypofractionated radiotherapy group vs 3.2% of the conventionally fractionated radiotherapy group (relative risk [RR] = 1.39, 95% CI = 0.75–2.55). Late grade ≥ 3 genitourinary adverse events occurred in 4.2% of the hypofractionated radiotherapy group vs 3.4% of the conventionally fractionated radiotherapy group (RR = 1.26, 95% CI = 0.69–2.30).
The investigators concluded, “Long-term disease-free survival is noninferior with hypofractionated radiotherapy compared with conventionally fractionated radiotherapy. Biochemical failure is less with hypofractionated radiotherapy. No significant differences in late grade ≥ 3 gastrointestinal/genitourinary adverse events were observed between assignments.”
Dr. Lee, of Duke University Medical Center, 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.
