medwireNews: The 8-year results from the phase 3 CHHiP trial have confirmed the noninferiority of moderately hypofractionated radiotherapy delivering 60 Gy in 20 fractions to the conventional regimen for the control of localized prostate cancer.
However, the noninferiority of a hypofractionation schedule delivering 57 Gy in 19 fractions could not be established.
Both findings align with the previously reported 5-year outcomes, said presenter David Dearnaley (Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, UK) at the 2020 Genitourinary Cancers Symposium in San Francisco, California, USA.
Explaining the rationale for the longer follow-up, which was a median of 9.3 years for the current analysis, he said: “Moderate hypofractionation is now an international standard of care but with patients remaining at risk of recurrence for many years, information on long-term outcomes is important.”
Among the 3216 trial participants – all of whom had node-negative, T1b–T3a localized disease – the rate of biochemical or clinical failure-free survival at 8 years was 83.7% for the men who were randomly assigned to receive the 60 Gy regimen, 78.5% for those given the 57 Gy regimen, and 80.6% for those who received the conventional regimen of 74 Gy in 37 fractions.
The hazard ratio (HR) for biochemical or clinical failure for the comparison of the 60 Gy to the conventional schedule was 0.85 and the 90% confidence interval was within the prespecified limit of 1.21, which confirmed the noninferiority of the hypofractionated regimen.
But for the 57 Gy schedule, the HR was 1.17 and the upper boundary of the confidence interval exceeded the prespecified value and therefore noninferiority could not be established.
Dearnaley also presented an update to an exploratory analysis by age, which showed similar findings among men aged younger than 75 years to the overall cohort, but pointed to better biochemical or clinical failure-free survival among older patients with the 57 Gy schedule versus the control. In this latter group, the 8-year rates were 86.7%, 81.6%, and 77.1% with the 60 Gy, 57 Gy, and conventional regimen, respectively.
Therefore, “hypofractionated radiotherapy using 57 Gy continues to be an option” in this older age group, he commented.
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2020 Genitourinary Cancers Symposium; San Francisco, California, USA: 13–15 February