Ultra-hypofractionated and conventionally fractionated radiotherapy for intermediate- or high-risk prostate cancer (PCa) are associated with similar 5-year rates of failure-free survival, new study findings suggest.

As part of the phase 3 HYPO-RT-PC noninferiority, randomized control trial (RCT), Anders Widmark, MD, Umeå University in Umeå, Sweden, and collaborators randomly assigned 1200 men with intermediate- or high-risk PCa to received conventional fractionation (78 Gy in 39 fractions, 5 days per week for 8 weeks; 602 patients) or ultra-hypofractionation (42.7 Gy in 7 fractions, 3 days per week for 2.5 weeks; 598 patients). The median follow-up time was 5 years.

The estimated 5-year rate of failure-free (biochemical or clinical) survival was 84% in both treatment arms, Dr Widmark’s team reported in The Lancet.

The investigators observed no significant differences between the groups in grade 2 or worse urinary or bowel late toxicity at any point after radiotherapy, except for a significant increase in urinary toxicity in the ultra-hypofractionation group compared with the conventional fractionation group at the 1-year follow-up (6% vs 2%).

“The outcomes of the HYPO-RT-PC trial are specifically relevant for patients with intermediate-risk disease because there were few high-risk patients in the trial,” the investigators wrote. “Our results support the use of image-guided ultra-hypofractionated radiotherapy for prostate cancer.”

The new study, which is the first randomized trial comparing ultra-hypofractionation to conventional hypofractionation in men with intermediate- or high-risk PCa, confirms the findings of cohort studies suggesting that extreme hypofractionation leads to promising progression-free survival and acceptable morbidity, the authors wrote. “There is now enough evidence from several large trials to suggest that conventional fractionation for intermediate-risk prostate cancer can be considered unconventional.”

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Hypofractionation will benefit patients by shortening treatment time and the health care system by lowering treatment costs, according to Dr Widmark and his team. “However, sophisticated image guidance of treatment is probably a prerequisite. The same conclusion is not valid for high-risk patients owing to a lack of studies and, perhaps, a different biology.”

In an accompanying editorial, Charles Catton, MD, of the University of Toronto, and Himu Lukka, MD, of McMaster University in Hamilton, Ontario, commented that the new study “provides the strongest data to date supporting the use of ultra-hypofractionation for intermediate-risk prostate cancer.”

They added, however: “It would be prudent to await longer follow-up and additional data from ongoing large RCTs evaluating ultra-hypofractionation regimens (PACE-NCT01584258 and GU005-NCT03367702) before this approach is considered the new external beam radiotherapy standard in treating intermediate-risk prostate cancer.”

Reference

Widmark A, Gunnlaugsson A, Beckman L, et al. Ultra-hypofractionated versus conventionally fractionated radiotherapy for prostate cancer: 5-year outcomes of the HYPO-RT-PC randomised, non-inferiority, phase 3 trial. Lancet. 2019;394:385-395. 10.1016/S0140-6736(19)31131-6

Catton C, Lukka H. The evolution of fractionated prostate cancer radiotherapy. Lancet. 2019;394:361-362. doi: 10.1016/S0140-6736(19)31338-8