Modulation of dose intensity in aerodigestive tract cancers: strategies to reduce toxicity.

Advances in diagnostic and therapeutic radiology and a better understanding of cell biology are being applied in practical ways to modulate treatment morbidity. Conformal radiotherapy targets the cancer precisely and can be combined with new systemically administered radiosensitizers. The successes of conventional chemoradiation programs support continued study of newer ways to deliver systemic radiosensitizing chemotherapy. However, chemoradiation creates a narrower therapeutic window compared to irradiation alone and increased treatment intensity, even with conformal chemoradiation techniques, can potentially result in frequent complications, detrimental treatment delays, and decreased quality of life. Treatment schedules employing a "best tolerated time" modelfor systemic administration of radiosensitizing chemotherapy, based on the concept of chronotolerance, offer attractive ways to address the challenging problem of normal tissue toxicity associated with conformal chemoradiation. This approach may be beneficial in the elderly and those medically unfit to tolerate traditional dose-intense combined-modality schedules. Further evaluation of this concept is warranted, based on existing data.