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Altered fractionation for head and neck cancer.

A conventional course of radiation for squamous cell carcinoma in the United States is generally 70 Gy in 7 weeks, with a once-daily dose of 1.8 to 2 Gy. This schedule has a modest success rate in curing head and neck cancer. The past several decades have seen numerous investigations into altering this schedule to optimize the results of radiation. Two approaches, founded on radiobiologic principles and clinical observations, have been tested with overlap between both concepts. Hyperfractionation is based on the ability to deliver radiotherapy in small fractions and increased total doses, while not adding to late toxicity. Accelerated fractionation is based on the observations that radiation injury causes accelerated tumor clonogen repopulation and that shortening the overall treatment time helps overcome this phenomenon. Both approaches have been shown to result in modest gains when tested in randomized trials, culminating with the completion of a Radiation Therapy Oncology Group trial (RTOG 9003). This randomized trial of more than 1,000 patients addressed various fractionation schedules proposed to improve results for head and neck cancer patients treated with radiation.