MedWire News: Three-year rates of freedom from biochemical failure (FFBF) achieved after hypofractionated radiotherapy (HFR) for prostate cancer are significantly better than those obtained after conventional fractionation radiotherapy (CFR), report researchers.
By contrast, and despite the authors' hypothesis that the incidence of late toxicity would decrease after HFR, toxicity rates were found to be equivalent for the two treatment types.
Giorgio Arcangeli (Regina Elena Cancer Institute, Rome, Italy) and colleagues explain that, for elderly patients and those who live at a distance from radiotherapy centers, "a reduced number of higher-dose fractions to a biologically equivalent total dose (hypofractionation) should be less distressing."
They add that HFR "should also result in reduced treatment costs and shorter waiting periods for patients who need to initiate radiotherapy as soon as possible."
The researchers investigated whether an HFR regimen designed to be equivalent to a CFR regimen with regards to tumor control, would reduce late toxicity without decreasing FFBF.
A total of 168 patients with high-risk (biopsy Gleason score 8-10, pre-treatment prostate-specific antigen [iPSA] level >20 ng/ml, or the presence of at least two of the following: iPSA 11-20 ng/ml, T stage 2c or higher, or Gleason score 7) were randomly assigned to receive HFR (n=83) or CRT (85).
After a median follow-up of 35 and 32 months for the HFR and CFR groups, respectively, the researchers found no significant difference in gastrointestinal or genitourinary complication rates.
Three-year incidence rates of late complications (Grade 2 or higher on the Late Effects in Normal Tissues Subjective, Objective, Management, and Analytic scale) in the HFR and CFR groups were 17% and 14%, respectively, for gastrointestinal, and 16% and 11%, respectively, for genitourinary complications.
Overall, 24 (14%) patients experienced biochemical failure - defined as a PSA level 2 ng/ml above the nadir - with more in the CFR group than in the HFR group, at 16 (19%) versus 8 (10%).
Correspondingly, FFBF rates were significantly different for patients treated with HFR versus CFR, with 3-year actuarial FFBF rates of 87% and 79%, and 4-year rates of 82% and 60%, respectively.
Multivariate analysis revealed that HFR resulted in an approximately 70% reduction in the risk for biochemical failure, and the hazard ratio for this increased by 2.2% for each 1 ng/ml increment in iPSA.
"The significant improvement of biochemical response observed with hypofractionation supports the radiobiological assumptions of the high sensitivity of prostate tumors to large dose fractions," Arcangeli et al conclude in the International Journal of Radiation Oncology Biology Physics.
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