The Efficacy and Safety of Conventional and Hypofractionated High-Dose Radiation Therapy for Prostate Cancer in an Elderly Population: A Subgroup Analysis of the CHHiP Trial

Abstract

Outcome data on radiation therapy for prostate cancer in an elderly population are sparse. The CHHiP (Conventional or Hypofractionated High Dose Intensity Modulated Radiotherapy in Prostate Cancer) trial provides a large, prospectively collected, contemporary dataset in which to explore outcomes by age. CHHiP participants received 3 to 6months of androgen deprivation therapy and were randomly assigned (1:1:1) to receive 74Gy in 37 fractions (conventional fractionation), 60Gy in 20 fractions, or 57Gy in 19 fractions. Toxicity was assessed using clinician-reported outcome (CRO) and patient-reported outcome questionnaires. Participants were categorized as aged < 75years or ≥ 75years. Outcomes were compared by age group. Of 3216 patients, 491 (15%) were aged≥75years. There was no difference in biochemical or clinical failure rates between the groups aged < 75years and ≥ 75years for any of the fractionation schedules. In the group aged ≥ 75years, biochemical or clinical failure-free rates favored hypofractionation, and at 5years, they were 84.7% for 74Gy, 91% for 60Gy, and 87.7% for 57Gy. The incidence of CRO (grade 3) acute bowel toxicity was 2% in both age groups.The incidence of grade 3 acute bladder toxicity was 8% in patients aged<75years and 7% in those aged≥75years.The 5-year cumulative incidence of CRO grade≥2 late bowel side effects was similar in both age groups.However, in the group aged≥75years, there was a suggestion of a higher cumulative incidence of bowel bother (small or greater) with 60Gy compared with 74Gy and 57Gy. Patient-reported bladder bother was slightly higher in the group aged ≥ 75years than the group aged < 75years, and there was a suggestion of a lower cumulative incidence of bladder bother with 57Gy compared with 74Gy and 60Gy in patients aged ≥ 75years, which was not evident in those aged < 75years. Hypofractionated radiation therapy appears to be well tolerated and effective in men aged ≥ 75years. The 57-Gy schedule has potential advantages in that it may moderate long-term side effects without compromising treatment efficacy in this group.