Second primaries in children with central nervous system tumors.

Among 670 children diagnosed with central nervous system tumors before age 20 and recorded in the Connecticut Tumor Registry, nine had a second neoplasm as well. From known age-specific and year-specific cancer incidence figures for Connecticut, the expected number of second neoplasms for the series of 670 is 0.99; therefore the relative risk is 9.1 (95% confidence limits: 4.0, 17.3). Three patients developed two central nervous system tumors, while 0.16 were expected, giving a relative risk of 19 (95% confidence limits: 3.8, 55). Six patients developed two neoplasms in childhood, versus 0.66 expected; the relative risk of this event is 9.1 (95% confidence limits: 3.3, 20). In four cases of lapse in time between the diagnosis of the first and second tumor, the first tumor had been treated with radiation. Five cancers occurred in parents or siblings of these nine patients, versus 0.91 expected; the relative risk is 5.5 (95% confidence limits: 1.2, 10.0). Three of these relatives had leukemia, while only 0.04 cases were expected (relative risk = 75). We conclude that not only is a child with CNS cancer at increased risk for other cancers, but such a child with two cancers is often part of a familial cluster with increased risk of cancer.