Tumor control probability (TCP) and normal tissue complication probability (NTCP) in head and neck cancer.

Clinical radiobiology is concerned with the relationship between a given radiation dose and the resulting biological effect on tumors and normal tissues, as well as with all confounding factors related to the delivery of radiation (e.g. dose per fraction, overall treatment time, volume of tumor/normal tissue irradiated, concomitant use of chemotherapy) and/or associated with preexisting conditions of the host (e.g. diabetes, hypertension, genetic syndromes) that may influence this relationship. This article briefly reviews few of the concepts associated with the dose-effect relationships in both normal tissues and tumors of the head and neck area and presents an operational way to integrate all these concepts into the routine radiotherapy planning processes.