The Role of Radiation Therapy With 5-Fluorouracil in Anal Cancer.

The most commonly used initial treatment of primary epidermoid cancer of the anal canal is radiation combined with concurrent 5-fluorouracil (5-FU) and mitomycin. Randomized trials have shown that these drugs, when combined with split-course or moderate-dose radiation, are superior to the same doses of radiation delivered without drugs. In another trial, the addition of mitomycin to 5-FU resulted in a better outcome thand when 5-FU alone was combined with radiation. Studies are in progress to evaluate treatment with radiation plus 5-FU and cisplatin; this combination has also produced high rates of tumor response in preliminary studies. The optimal schedules and doses of 5-FU to combine with radiation are not known-common usage favors 96- or 120-hour infustions of 5-FU at a dose of 750 to 1,000 mg/m(2)/24 hours, generally administered as one or two courses concurrently with conventional once-daily fractionated radiation. It is unclear whether 5-FU in these combinations is acting as a cytotoxic agent, a radiosensitizer, or both. Despite these uncertainties, empiric clinical studies have led to the development of effective treatment regimens that allow conservation of anorectal function in the majority of patients with anal cancer.