[Second primary malignant neoplasm following radiation therapy of head and neck cancers].

This retrospective analysis reports the results of radiotherapy in 8272 patients with cancer who were treated at Tokyo Women's Medical College between 1966 and 1984. One thousand one hundred and four cases were irradiated for head and neck tumor during this period. Twenty-nine of the total number of patients (0.35%) were found to have second primary malignant neoplasms following radiotherapy according to the criteria of radiation-induced or related cancers. Twenty of these were head and neck tumors with an incidence of 1.81% among all head and neck cancer patients. If recurrence of highly suspected cases was excluded, the incidence of radiation-induced or -related cancer was 0.18% among all malignancies and 0.63% among all head and neck tumors. Cases of multiple primary malignant neoplasm have been increasing in number and second cancer following radiotherapy has gradually become a big problem. However, the mechanisms of cancer etiology on which radiation and many other factors have an influence are not clear at this time, as there are many risks to human life. It is important not to underestimate the value of radiotherapy in cancer treatment today.