Incidence of second malignant neoplasms in children: results of an international study.

The incidence of second malignant neoplasms (SMNs) in children was estimated from data provided by ten paediatric oncology centres. During 1950-70 nearly 15 000 new patients were seen at these institutions. With follow-up through 1979, 113 eligible cases of SMN were reported. To estimate the number of person-years at risk, a common set of survival distributions, specific for tumour type and calendar period, was applied to the patient entry data at each institution. The annual incidence of SMNs 5-15 years after diagnosis of first tumour was found to be 188/100 000; this represents an approximate ten-fold increase over the age-adjusted expected rate of cancer in the general population. The corresponding incidence during the first 5 years was 85/100 000/year, a seven-fold increase in risk. The estimated cumulative probability of SMN reached 3.3% at 20 years.