Three-Arm Trial Suggests Middle Ground for Hypofractionation RT for Prostate Cancer

A large three-arm trial found that one hypofractionation radiotherapy (RT) regimen was non-inferior to conventional RT for mostly intermediate-risk prostate cancer patients, while a second hypofractionation approach did not reach that endpoint. Results were presented at the 2016 American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium, held January 7–9 in San Francisco (abstract 2).

The CHHiP trial randomized 3,216 patients who had previously received hormone therapy to one of three groups: conventional RT totaling 74 Gy delivered as 37 fractions over 7.4 weeks; hypofractionated RT totaling 60 Gy delivered in 20 fractions over 4 weeks; or hypofractionated RT totaling 57 Gy delivered in 19 fractions over 3.8 weeks. Results of the trial were presented by David P. Dearnaley, MD, of the Royal Marsden and Institute of Cancer Research in the United Kingdom.

The patients had a median age of 69 years. Most of the patients (73%) were intermediate-risk; 12% were high-risk, and 15% were low-risk. Most patients had a clinical stage of T1 (36%) or T2 (55%), and the median pre-hormone prostate-specific antigen (PSA) level was 10 ng/mL.

The 5-year control rates were 88.3% for the conventional RT group (control), 90.6% with the 60-Gy regimen, and 85.9% for the 57-Gy group. Compared with the control, the 60-Gy group had a hazard ratio (HR) of 0.84 (90% confidence interval [CI], 0.68–1.03; P = .004), which met the prespecified criteria for non-inferiority. The 57-Gy group, however, had an HR of 1.20 (90% CI, 0.99–1.46; P = .96), which did not meet that endpoint.

The 60-Gy group also fared better in a direct comparison with the 57-Gy group. The HR for 57 Gy vs 60 Gy was 1.44 (95% CI, 1.13–1.82; P = .003), meaning 57 Gy was statistically inferior to 60 Gy.

With regard to toxicity, there was some difference in late bowel effects, with 57 Gy performing better than 60 Gy, though neither was statistically different from the control group. This was similar for late bladder effects as well. With regard to sexual toxicities, there were no differences between the three groups.

“We believe that modest hypofractionation using 60 Gy and 20 fractions, delivered with high-quality radiotherapy techniques, can now be recommended as a new standard of care” in this patient population, Dearnaley concluded.

The discussant for the session, Daniel Hamstra, MD, PhD, of the Texas Center for Proton Therapy in Irving, Texas, wondered whether implementation of these and other similar findings will move quickly or not. He noted that uptake of hypofractionation for breast cancer, for which research is 5 to 10 years ahead of prostate cancer, has been relatively slow in the United States. “It will be intriguing to see whether or not this type of modest hypofractionation takes off,” he said.