Head and neck cancers Radiation Therapy

Radiotherapy plays an integral role in the treatment of most head and neck cancers. Used as the sole modality for the treatment of select early-stage disease (T1 and T2), it gives comparable results to a surgical resection, often with less morbidity. For tumors arising in the larynx, it may be preferred to surgery because it maintains organ function. For intermediate sized lesions, it is used as an adjuvant to surgery in order to improve locoregional control.

When used as an adjuvant, it is important that there be good communication between the surgeon and the radiation oncologist in order to avoid inadvertent delays that can compromise outcome. For example, Vikram and colleagues have noted that the rate of locoregional tumor recurrence was greater if there was more than a 6-week delay between surgery and the initiation of adjuvant radiotherapy. The adverse impact of a delay in beginning treatment has been confirmed by Mackillop and colleagues, who found an approximate 10% lowering of local control in patients with advanced tonsillar carcinoma per month of delay in beginning radiotherapy. For advanced inoperable lesions and for tumors arising in certain sites such as the nasopharynx, radiation therapy may be the only potentially curative modality. Its effectiveness has been increased by the concomitant use of chemotherapy and by using more optimal treatment fractionation schemas (discussed below).

Ionizing radiation (high-energy photons, electrons, neutrons, protons, and other charged particles) interacts with matter in subtle ways and should not be thought of as simply a form of cautery. Tumors and normal tissues can vary dramatically in their ability to repair the cellular damage caused by ionizing radiation. This makes it possible to use treatments such as chemotherapy and hyperthermia to reduce the repair capability of tumors and to design fractionation schemes that effectively widen the therapeutic window between tumor control and normal tissue damage.
HNSCCs are generally characterized as being "moderately radiosensitive," meaning that fairly large amounts of radiation must be delivered in order to achieve a high probability of tumor control. Fortunately, the required doses are within the tolerance range of most tissues in the head and neck.

The effectiveness of a given dose of radiation depends upon how it is given. Over the past 30 years, various "standard" treatment regimens have evolved to treat head and neck cancer. In the United States the traditional "curative" treatment regimen consists of giving 180 to 200 cGy once a day for 5 days a week to a total dose of 6,500 to 7,400 cGy; in England and Canada, higher daily doses of 220 to 250 cGy are given once a day for 5 days a week to a total dose of 5,000 to 5,500 cGy. These two schemas have evolved empirically, and a review of the literature seems to indicate that they provide comparable tumor control with the main debate relating to differences in complications. Various altered fractionation regimens have been compared to the standard regimens in clinical trials and some of these appear to be evolving into new "standards."