November 05, 2013
2 min read

Hypofractionated IMRT did not improve prostate cancer outcomes

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Hypofractionated intensity-modulated radiation therapy did not reduce biochemical or clinical disease failure compared with conventional fractionation in a cohort of patients with prostate cancer, according to study results.

In addition, compromised urinary function worsened after treatment with hypofractionated intensity-modulated radiation therapy (IMRT).

Researchers enrolled 303 men with favorable- to high-risk prostate cancer between 2002 and 2006. Of them, 152 were randomly assigned to conventional fractionation IMRT totaling 76 Gy, administered in 38 fractions of 2.0 Gy. The other 151 patients were assigned to hypofractionated IMRT totaling 70.2 Gy, administered in 26 fractions of 2.7 Gy.

Patients defined as high risk underwent 24 months of androgen deprivation therapy (ADT). Low-risk patients received 4 months of ADT prior to IMRT.

Biochemical and clinical disease failure — defined as local failure and regional or distant metastasis — served as the primary outcome. Toxicity was a secondary endpoint.

Median follow-up was 68.4 months.

Results showed no significant differences in 5-year biochemical or clinical disease failure between conventional fractionation (21.4%; 95% CI, 14.8-28.7) and hypofractionated IMRT (23.3%; 95% CI, 16.4-31).

T category, Gleason score, initial PSA and length of ADT were significantly associated with the primary outcome measure.

Overall, occurrence of gastrointestinal and genitourinary toxicity did not differ between the treatment groups.

Results of a subanalysis indicated that patients who underwent hypofractionated IMRT and who had a baseline International Prostate Symptom Score > 12 were more likely to experience grade ≥2 late genitourinary reactions (P.001).

The advantages of the shorter duration with hypofractionation must be weighed against the efficacy data, W. Robert Lee, MD, of Duke University School of Medicine, wrote in an accompanying editorial.

Three noninferiority trials also are underway to compare moderate hypofractionation with conventional fractionation in patients with prostate cancer. Preliminary results are expected within 3 years, Lee wrote.

“Considering all the information to date, it might not be prudent to move from the current standard of 1.8-2 Gy. There is simply no strong evidence that moderate hypofractionation is superior to conventional fractionation,” Lee wrote. “If, and it is a big if, the noninferiority trials suggest that moderate hypofractionation is no worse than conventional fractionation, then the burden of proof will be met and, for patient convenience and cost reasons, moderate hypofractionation should be the standard of care.”

Disclosure: Researchers report consultant or advisory roles with, as well as honoraria or research funding from, Augmenix, Calypso, GE Healthcare, Philips Healthcare, Siemens Healthcare and Varian Medical Systems.