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Time‐dose relationships and brachytherapy in radiation oncology of head and neck cancer

The time-dose relationship plays a critical role in the optimization of radiation therapy for tumors at any site. The recognition that altered fractionation schemes can be used to increase total delivered dose with similar delayed effects has prompted many new studies. These studies have shown improved local control for some stages and sites of head and neck cancer. The discovery that accelerated repopulation of clonogenic cells can occur clinically has led to the design and implementation of new approaches for radiation delivery. The advent of high dose rate afterloading techniques for brachytherapy also has an impact on the total delivery of definitive doses and will require investigation of high dose rate relative to low dose rate implant techniques. Finally, combining altered fractionation radiotherapy and chemotherapy to extend nonsurgical treatment to its radical limits must be investigated for safety and efficacy.