Hypofractionated RT in Low-Risk Prostate Cancer Produces Similar Results

Hypofractionated radiation therapy appears to lead to similar efficacy and safety as a standard radiation therapy regimen for men with low-risk prostate cancer. The results of the phase III Radiation Therapy Oncology Group (RTOG) 0415 study comparing the two types of regimens were presented at the 57th Annual Meeting of the American Society for Radiation Oncology (ASTRO), held October 18–21 in San Antonio, Texas (LBA 6).

After a median of 5.9 years, the analysis showed that hypofractionated and conventional radiation therapy had similar disease-free survival. The estimated 7-year disease-free survival rates were 76% and 82% in the conventional and hypofractionated radiation therapy study arms, respectively.

The RTOG trial randomized 1,105 men with low-risk prostate cancer to receive either conventional radiation therapy with 73.8 Gy in 41 fractions given over 8.2 weeks or the shorter course therapy of 70 Gy in 28 fractions given over 5.6 weeks.

“This is the first large-scale, randomized study demonstrating the value of a shorter course of radiation therapy for low-risk prostate cancer patients,” said Howard M. Sandler, MD, MS, FASTRO, co-author of the study and professor and chair of the department of radiation oncology at Cedars-Sinai Medical Center, in a statement. “The results are not surprising, however, given that studies on the effects of hypofractionated radiation therapy in patients with early-stage breast cancer, which is similar to early-stage prostate cancer, have demonstrated similar outcomes,” added Sandler.

Patients had a median age of 65 and a median pretreatment prostate-specific antigen (PSA) score of 5.4 ng/mL. Men studied had clinical stage T1–2a disease, a Gleason score of 6 or less and PSA score of less than 10.

Both biochemical recurrence, as measured by PSA score, and overall survival in the hypofractionated arm were non-inferior to the standard radiation therapy arm (hazard ratios of 0.77 and 0.95, respectively).

Rates of grade 3 late side effects were similar among the two treatment arms. In patients receiving conventional radiation therapy, 3% had gastrointestinal side effects compared with 5% in the hypofractionated arm. Genital or urinary side effects were similar between the two arms as well-5% in the conventional arm compared with 6% in the hypofractionated arm.