2ND MALIGNANT NEOPLASMS AFTER CANCER IN CHILDHOOD OR ADOLESCENCE

Objective-To assess the relative risk of developing a second malignant neoplasm in people with a diagnosis of cancer in childhood and adoles cence. Design-Register based follow up study. Setting-Populations of N ordic countries. Subjects-30 880 people under the age of 20 with a fir st malignant neoplasm diagnosed during the period 1943-87. Main outcom e measures-Relative and attributable risks of second malignant neoplas ms by type of first cancer, age at first diagnosis, calendar period, s ex, and country. Expected figures were based on the appropriate nation al incidence rates for cancer. Results-247 cases of second malignant n eoplasms were observed in 238 patients, yielding a relative risk for c ancer of 3-6 (95% confidence interval 3.1 to 4.1). The risk changed si gnificantly from 2.6 in people first diagnosed during the 1940s and 19 50s to 6.9 among cohort members included in the late 1970s and 1980s. Increases were observed for most types of cancer. Highest levels of th e relative risk were seen during the 10 years immediately after first malignant diagnosis. The incidence of second malignant neoplasms attri butable to the first cancer and associated treatments, however, showed a consistent rise throughout the 45 years of follow up. Conclusion-Th e estimated risks for a second malignant neoplasm were significantly l ower than those found in most large hospital based studies but compati ble with the results from a similar population based study in the Unit ed Kingdom. Extent of risk and cancer pattern were similar among the N ordic countries and are believed to be representative for a large part of the European population.