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A novel chemoradiation regimen for the treatment of anal cancer is proven to have fewer significant side effects than conventional therapy while remaining just as effective.

The 2-year outcomes for dose-painted intensity-modulated radiation therapy (DP-IMRT) with 5-fluorouracil (5FU) and mitomycin C (MMC) used in the Radiation Therapy Oncology Group (RTOG) trial 0529 were similar to those seen in the 5FU/MMC/conventionally delivered radiation arm of RTOG 9811. The latter regimen is the standard of care for US patients with nonmetastatic squamous cell cancer of the anal canal. However, as RTOG 0529 principal investigator Lisa Kachnic, MD, chair of radiation oncology at Boston University, has stated, the treatment results in long-term disease-free survival but is associated with significant acute toxicity, partially due to the large radiation fields used.

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Conventionally delivered radiation therapy involves two- or three-dimensional fields that treat normal as well as diseased organs. In contrast, IMRT conforms, or “paints,” the radiation dose to the tumor and lymph nodes, sparing healthy surrounding tissue.

An outcomes analysis of 52 patients with stage II or stage III anal cancer who had been treated with IMRT and 5FU/MMC chemotherapy showed overall survival was 86% and 2-year disease-free survival was 77% after a 26.7-month median follow-up period. These rates were comparable to the 2-year overall and disease-free survival rates of 91% and 75%, respectively, seen among the 325 patients who underwent conventional radiation with 5FU/MMC in RTOG 9811.

The difference, however, was in the side effects: The use of IMRT was associated with significantly less grade 3+ gastrointestinal and dermatologic acute toxicity. “Because of the associated acute toxicity sparing, DP-IMRT will be used as the platform, and may allow for radiation dose escalation, in future RTOG anal canal trials,” noted the research group. ONA