Shorter radiotherapy duration feasible in high-risk prostate cancer

A 5-week course of hypofractionated radiation therapy induced similar mortality and recurrence rates as a conventional 8-week course, according to findings presented at the 2022 ASTRO Annual Meeting.1,2

In the multicenter, randomized phase 3 trial (NCT01444820), researchers assessed 329 patients who received a conventional duration of radiation therapy (76 Gy in 38 daily sessions over approximately 8 weeks) or a shorter, 5-week duration of radiation therapy (68 Gy in 25 daily sessions over 5 weeks). All patients also received long-term androgen deprivation therapy (ADT) prior to, during, and after radiation therapy, as well as pelvic lymph node radiation.

Seven-year outcomes showed an overall survival rate of 81.7% and a prostate cancer-specific mortality rate of 94.9% in the 5-week treatment group in comparison to 82% and 96.4%, respectively, for those receiving 8 weeks of radiation.

The authors of the phase 3 trial also noted similar biochemical recurrence rates (87.4% in the accelerated treatment group vs. 85.1% in the 8-week treatment group) and distant metastatic recurrence rates (91.5% for those who had 5 weeks of radiation vs. 91.8% in the 8-week treatment group).

“I think this trial will pave the way for patients with high-risk prostate cancer to be treated in 5 weeks instead of 8 weeks. Many of these patients are still offered 8 weeks of radiation therapy, but our trial found no benefit to the extra three weeks,” lead study author Tamim M. Niazi, MD, an associate professor of Oncology at McGill University in Montreal, stated in a news release.

Noting that the radiological properties of prostate cancer cells are particularly sensitive to modifications in the fraction size of radiation treatment, 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.

Niazi said 8 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.

Potential next steps for this research, according to Niazi, include exploring “ultra-hypofractionation” in patients with favorable high-risk disease by further reducing the number of fractions; intensifying hormone therapy in patients with very high-risk disease; and improving patient selection for more or less aggressive treatment through the use of genetic biomarkers.

References

1. Shortened course of radiation therapy safe and effective for men with high-risk prostate cancer. Published online October 23, 2022. https://bit.ly/3FYbhN3

2. Niazi TM, Nabid A, Malagon T et al. Conventional vs. Hypofractionated, Radiotherapy for High-Risk Prostate Cancer: 7-Year Outcomes of the Randomized, Non-Inferiority, Phase 3 PCS5 Trial. Int J Radiat Oncol Biol Phys.114(3). doi:10.1016/j.ijrobp.2022.07.2323