UNLABELLED - Hypothetically, any site in a radiation portal has potential for late malignant transformation. Secondary malignant neoplasms may occur after almost any index cancer has been treated with radiation and/or chemotherapy. The incidence of secondary malignant neoplasms, histopathology, time delay, radiation dose, cytotoxic agents, age and type of initial malignancy, and outcome all negatively impact cancer survivors. We highlight the new concept of multifocality, defined as greater than two noncontiguous second malignant neoplasms that develop in a prior radiation port. We identified 48 patients with postradiation sarcomas from three prospectively collected databases. Fifteen of these patients (31%) had evidence of multifocal postradiation sarcomas. Five of 10 women had multifocal postradiation sarcomas after breast-conserving surgery for carcinoma. The longer the time interval between the index cancer and post-radiation sarcoma, the greater the likelihood of multifocal malignant transformation occurring.
LEVEL OF EVIDENCE - Therapeutic study, level III.