Study Suggests Shorter Duration of Radiation Therapy is Effective for High-Risk Prostate Cancer

In what is reportedly the first study to reveal benefits of hypofractionated radiation therapy for men with high-risk prostate cancer, new research demonstrated that five weeks of radiation therapy had similar mortality and recurrence rates as the traditional eight-week duration of radiation treatment.

For the multicenter, randomized trial, researchers assessed 329 patients who received a conventional duration of radiation therapy (76 Gy in 38 daily sessions) or a shorter, five-week duration of radiation therapy (68 Gy in 25 daily sessions). All patients in the study also received long-term androgen deprivation therapy (ADT) prior to, during and after radiation therapy as well as pelvic lymph node radiation, according to the study.

Seven-year outcomes showed an overall survival rate of 81.7 percent and a prostate cancer-specific mortality rate of 94.9 percent in the five-week treatment group in comparison to 82 percent and 96.4 percent, respectively, for those receiving eight weeks of radiation, according to the researchers, who recently presented their findings at the American Society for Radiation Oncology (ASTRO) Annual Meeting in San Antonio, Texas.

The authors of the phase III trial also noted similar biochemical recurrence rates (87.4 percent in the accelerated treatment group vs. 85.1 percent in the eight-week treatment group) and distant metastatic recurrence rates (91.5 percent for those who had five weeks of radiation vs. 91.8 percent in the eight-week treatment group).

“I think this trial will pave the way for patients with high-risk prostate cancer to be treated in five weeks instead of eight weeks. Many of these patients are still offered eight weeks of radiation therapy, but our trial found no benefit to the extra three weeks,” noted lead study author Tamim M. Niazi, M.D., an associate professor of oncology at McGill University in Montreal.

Noting that the radiological properties of prostate cancer cells are particularly sensitive to modifications in the fraction size of radiation treatment, Dr. Niazi said the goal of the study was to assess whether a moderate increase in daily radiation treatment could achieve similar control of prostate cancer as conventional fractionation but over a shorter duration of treatment.

In regard to short-term and long-term genitourinary and gastrointestinal toxicities, Niazi and colleagues said there were no significant differences between the two treatment groups, and no grade 4 toxicities in either group.

Dr. Niazi said eight weeks of radiation therapy should still be reserved for those with inflammatory bowel disease, patients who had remote pelvic radiation therapy for other indications and patients who had prior focal therapy prostate treatment.