Management of Cancer of the Head and Neck
Radiotherapy: General Guidelines

Many patients with early stage cancers of the head and neck can be adequately treated with radiation therapy as the sole modality. In the more advanced stages, combinations of radiation therapy with surgery or chemotherapy, or both, are necessary. During irradiation, trillions of "particles" of ionizing radiation interact with trillions of bases in the DNA of the cancer cells, causing DNA damage that leads to cell death. Therefore, the goal in radiation therapy is to deliver as high a dose of radiation to the target volume in as short a time as possible without causing unacceptable damage to the surrounding normal structures. To this end, various methods of delivering ionizing radiation (such as photons, electrons and brachytherapy) must be available to the radiation oncologist, to be employed as appropriate depending upon the clinical situation and the anatomical constraints.

Initial evaluation of the patient by the radiation oncologist requires a detailed head and neck examination, including fiberoptic endoscopy, to assess the extent of the cancer in the head and neck region. In addition, a detailed dental evaluation is necessary to determine the patient's initial suitability for irradiation, and to assess the risk of dental complications that may arise following irradiation. Review of systems and a detailed physical examination is necessary because patients usually require radiation therapy for several weeks and many also require concomitant chemotherapy. Patients requiring brachytherapy must be able to tolerate general or local anesthesia; they must be evaluated as any other pre-surgical patients. Systemic metastases must be ruled out by appropriate methods.

Treatment planning for radiation therapy is a complex process that requires, first of all, that the diagnosis of cancer be histopathologically proven. Next, a fluoroscopic simulation and/or computed tomographic ("virtual") simulation is performed, with the incorporation of fiducial markers that provide a frame of reference for the radiographic images that are fed into the treatment planning computer. In the case of brachytherapy, prior to simulation the radioactive seeds (permanent implants) or the non-radioactive "afterloading" applicators (temporary implants) must be placed in or near the cancer (this may be done in the operating room at the time of surgical extirpation of the tumor - tumor bed implant). In the case of external beam irradiation, prior to simulation an immobilizing device is made to ensure that the patient is always in the same position during simulation and treatment.

The radiation oncologist then draws on the radiographic images the target volumes (all the areas that are known to contain - or suspected of containing - cancer cells) as well as all the critical structures that must be protected to a greater or lesser degree from irradiation. In determining the target volume, he/she must synthesize all the information from the history and the physical examination, the imaging studies, the surgical findings and the pathological findings.

The radiation oncologist also determines the doses and techniques to be employed. The radiation physicist or dosimetrist then calculates the detailed radiation distribution in the body, producing isodose maps and dose-volume histograms. The radiation oncologist and physicist then interactively fine-tune ("optimize") these until they agree upon the best plan for that particular patient. In the case of external beam irradiation, customized shielding blocks are then prepared to shield the critical structures, either using an alloy (manually) or multi-leaf collimators (digitally). In the case of complex or unusual plans it is advisable to perform a verification in-vitro by doing a dry run, using a "phantom" instead of the patient.

Prior to delivering the first external beam treatment, the patient is positioned as if for treatment but radiographic "portal" images are obtained (on-line or off-line) to double check that the parameters are correct. Such images are repeated periodically throughout the course of treatment. Increasingly, in-vivo dose measurements are being performed to supplement the portal images.

In the case of afterloading brachytherapy the non-radioactive applicators are loaded with radioactive material, either manually with low dose-rate sources or by remote-controlled high dose-rate sources. The former requires several days of radioactive quarantine for the patient. The latter only takes a few minutes each day, which greatly facilitates the nursing care of the postoperative patient.

Acute toxicity during radiation therapy usually involves the skin and the mucous membranes. The patient is closely observed and supportive care is provided such as mouth and skin care, dental hygiene, with antibiotics and antifungals as necessary. Patients also receiving chemotherapy must be monitored for chemotherapy-related toxicity such as hemopoietic effects.

The most common chronic effect after irradiation of all of the major salivary glands is xerostomia, which in some patients may be relieved by pilocarpine. It is not clear at present whether amifostine is useful in preventing chronic xerostomia. Transposition of one submandibular gland out of the radiation field prior to irradiation is being explored to decrease chronic xerostomia. Hypothyroidism may occur after irradiation of the lower neck, particularly among patients who have undergone partial thyroidectomy. Lifelong good dental care including fluoride prophylaxis is very important for preventing osteoradionecrosis. Avoiding tobacco and alcohol, and nutritional counseling are not only important for the quality of life of patients with head and neck cancers but may also decrease the incidence of new cancers.