A hypofractionated high-dose intensity-modulated radiotherapy (IMRT) schedule consisting of 60 Gy over 20 fractions showed improved efficacy compared with 57 Gy over 19 fractions and was non-inferior to 74 Gy over 37 fractions with a similar low level of acute and delayed normal tissue damage, a study presented at the 2016 Genitourinary Cancers Symposium has shown.1

For the phase 3 CHHiP trial, researchers sought to explore the dose response relationship for two 3 Gy hypofractionated IMRT schedules for the treatment of T1b-3a N0 localized prostate cancer.

Researchers enrolled 3216 men with localized disease and randomly assigned them 1:1:1 to receive hypofractionated schedules of 60 Gy in 20 fractions or 57 Gy in 19 fractions, or conventional RT consisting of 74 Gy in 37 fractions. Of those, 15% had low-risk disease, 73% had intermediate-risk, and 12% had high-risk disease.

Results showed that at a median follow-up of 5.2 years, the 5-year progression-free survival rate was 88.3% (95% CI, 86.0 – 90.2) with 74 Gy, 90.6% (95% CI, 88.5 – 92.3) with 60 Gy, and 85.9% (95% CI, 83.4 – 88.0) with 57 Gy. Hazard ratios were 0.83 (90% CI, 0.68 – 1.03) for 60 Gy compared with 70 Gy, and 1.20 (90% CI, 0.99 – 1.45) for 57 Gy compared with 74 Gy.

Researchers observed significantly more progression events with the 57 Gy schedule compared with the 60 Gy schedule (HR, 1.44; 90% CI, 1.18 – 1.75; P = .003).

In regard to safety, there was no significant difference in gastrointestinal or genitourinary toxicity between the hypofractionated RT schedules. At 2 years, there was no statistically significant difference between the rates of genitourinary (P = .34) or gastrointestinal (P = .10) toxicities between the 3 arms.

Reference

  1. Dearnaley DP, Syndikus I, Mossop H, et al. Comparison of hypofractionated high-dose intensity-modulated radiotherapy schedules for prostate cancer: results from the phase III randomized CHHiP trial (CRUK/06/016). J Clin Oncol. 2016; 34 (suppl 2S; abstr 2).