[Second cancer. Risk of a second malignant neoplasm in persons with cancer in childhood and adolescence].

Cancer treatments in early life have in previous studies been associated in with high risks of developing a second malignant neoplasm. This study reports on the relative and attributable risks of second malignant neoplasms among 30,880 people under the age of 20, who had been identified in the files of any of the five Nordic cancer registers, 1943-1987. Overall, 247 cases of second malignant neoplasms were observed in 238 patients, yielding a relative risk for cancer of 3.6 (95% confidence interval 3.1-4.1). The risk changed significantly from 2.6 in people first diagnosed during the 1940s and 1950s to 6.9 among cohort members included in the late 1970s and 1980s. Highest levels of the relative risk were seen during the ten years immediately after first malignant diagnosis. The incidence of second malignant neoplasms attributable to the first cancer and associated treatments, however, showed a consistent rise throughout the 45 years of follow up. It was concluded that the estimated risks for second malignant neoplasms were significantly lower than those found in most large hospital based studies but compatible with the results from a similar population based study in the United Kingdom. Extent of risk and cancer pattern were similar among the Nordic countries and are believed to be representative for a large part of the European population.