Multiple primary malignant neoplasms in breast cancer patients in Israel.

The data of an epidemiologic study of multiple primary malignant neoplasms in breast cancer patients in Israel are presented. During the 18-year period of the study 12,302 cases of breast carcinoma were diagnosed, and, of these, 984 patients (8%) had multiple primary malignant tumors. Forty-seven of these patients developed two multiple primary cancers. A significantly higher than expected incidence of second primary cancers occurred at the following five sites: the opposite breast, salivary glands, uterine corpus, ovary, and thyroid. Cancers of the stomach and gallbladder were fewer than expected. Treatment of the breast cancer by irradiation was associated with an increased risk of subsequent cancers of lung and hematopoietic system. The prognosis was mainly influenced by the site and malignancy of the second primary cancer. The incidence of multiple primary malignancies justifies a high level of alertness to this possibility in the follow-up of breast cancer patients.