Second malignant tumors after cancer in childhood.

Studies were made of the development of second malignant tumors in children treated at the Sidney Farber Cancer Institute. In 1973 a retrospective analysis identified second cancers in 15 of 410 patients who survived a childhood cancer. During the period 5-24 years after diagnosis of the first cancer, the cumulative probability of developing a new cancer was 12%. This frequency was approximately 20-fold higher than the expected rate for the general population. Prospective study of the series since 1973 has identified a second primary cancer in five additional patients. The majority of second cancers were in the field of prior radiotherapy, and were attributable to the oncogenic effect of radiation. Genetic susceptibility factors were identified in individual patients.