Hypofractionation is non-inferior to conventional fractionation (redux)

It seems that several major randomized clinical trials of hypofractionation — fewer EBRT treatments at higher dose rates each — have all matured at the same time. While the recent Fox Chase trial focused on patients with intermediate- and high-risk, RTOG 0415 only included men with low-risk prostate cancer.

Between 2006 and 2009, 1,115 low-risk patients at about 300 sites in the US and Canada were randomly assigned to either hypofractionation or conventional fractionation:

  • Hypofractionation: 70 Gy in 28 fractions (2.5 Gy per fraction)
  • Conventional fractionation: 73.8 Gy in 41 fractions (1.8 Gy per fraction)
  • The hypofractionated biologically effective dose is 15 percent higher.

Lee et al. report that, after a median follow-up of 5.9 years:

  • 7-year disease-free survival (DFS) was 76 percent for conventional RT, and 82 percent for hypofractionated RT.
  • Late grade 3 urinary toxicity was 2.6 percent for conventional RT, 4.1 percent for hypofractionated RT, and were not significantly different.
  • Late grade 3 rectal toxicity was 2.3 percent for conventional RT, 3.5 percent for hypofractionated RT, and were not significantly different.

This gives us Level 1 evidence that hypofractionated radiation is not inferior to conventionally fractionated radiation in either oncological outcomes or toxicity in low-risk patients.

Taken together with the CHHiP trial and the Fox Chase trial, it will be hard to justify the added expense of a longer course of primary radiation therapy in any patient. Of course, this does not at all speak to whether even hypofractionated radiation is superior to active surveillance or to SBRT in low-risk patients. Only time will tell if it is practice changing. Radiation oncologists who bill per treatment will naturally be resistant, while insurance companies may encourage hypofractionation.

Editorial note: This commentary was written for The “New” Prostate Cancer InfoLink by Allen Edel.

One Response

  1. For those who have been diagnosed with low-risk prostate cancer (and who are reluctant to undertake active surveillance for some reason) and may be considering IMRT, the full text of this article is now available on line.

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