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 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% higher.
Lee at al. report after a median follow up of 5.9 years:
- · 7-year disease-free survival (DFS) was 76% for conventional RT, and 82% for hypofractionated RT.
- · Late grade 3 urinary toxicity was 2.6% for conventional RT, 4.1% for hypofractionated RT, and were not significantly different.
- · Late grade 3 rectal toxicity was 2.3% for conventional RT, 3.5% 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.