The risk of radiation-induced cancer in patients with squamous cell carcinoma of the head and neck and its results of treatment.

The purpose of this study was to determine the incidence and the results of treatment of cancer induced by radiotherapy for early stage (stage I and II) squamous cell carcinoma of the head and neck (SCH). The clinical records of 355 patients with early stage malignant lymphoma of the head and neck region treated by radiotherapy were reviewed, and then the records of 1358 patients with early stage SCH (oral cavity, 956; larynx, 154; oropharynx, 110; maxillary sinus, 86; lip, 20; epipharynx, 17; hypopharynx, 15) who underwent radiotherapy were reviewed. The disease-specific 10-year survival rate of the patients with 355 malignant lymphoma was 61%, and 5 cases of radiation-induced cancer occurred more than 8 years after irradiation. The crude incidence of radiation-induced cancer in the malignant lymphoma patients was 1.4%, and the 10-year probability by the actuarial life table method was 0.8%. The 10-year survival rate of the early stage SCH patients was 71%. The crude incidence of a second cancer in a previously irradiated field after an 8-year latent period (SCI) in the SCH patients was 1.8% (25/1358), and the 10-year probability was 1.6%. 12 SCIs were treated by surgery and 8 of those 12 patients (67%) resulted in success, whereas treatment by radiation resulted in failure in every other case. The risk of SCIs in the SCH group was higher than in the early stage malignant lymphoma group, although the difference was not statistically significant. The possibility of radiation-induced cancer in SCH is small, and the advantage of radiation therapy compares favourably with the risks of other treatments.