Second malignant tumors after elective end of therapy for a first cancer in childhood: a multicenter study in Italy.

To evaluate the incidence of second malignant tumors in a cohort of subjects previously treated for childhood cancer, we analyzed data from the Off-Therapy Registry (OTR) of the Italian Association of Pediatric Hematology/Oncology, which collects information on children treated for Hodgkin's disease, non-Hodgkin's lymphoma, Wilms' tumor, acute lymphoblastic leukemia (ALL) and acute non-lymphatic leukemia and who had been removed from treatment in the absence of clinical signs of disease, i.e. the off-therapy stage. Second malignant tumors (SMT), diagnosed before December 31, 1988, were identified through a special enquiry to the 36 institutions cooperating in the registry. Observed cases were compared to expected numbers estimated from age- and sex-specific incidence rates derived from the Cancer Registry of the Province of Varese. In a total of 3,310 study subjects, 27 SMTs have been registered. The Cumulative Risk (CR) of SMT was 2.9% 15 years after the end of treatment and the Standard Incidence Ratio (SIR) was 10.8. The ALL sub-cohort had the highest risk of SMT (SIR 13.6) and 9 cases of CNS tumor occurred in this group (SIR 58.9). All 9 had received prophylactic cranial radiotherapy (CRT) and 5 had been treated on one protocol, characterized by low-dose intrathecal methotrexate (IT MTX) given monthly for 2 years after CRT. The Off-Therapy Registry has unique criteria for inclusion; direct comparisons with similar studies are therefore somewhat problematic. However, our data suggest that the risk of SMT in childhood ALL cancer survivors may be greater than previously reported, and that CNS tumors are the most common SMT in this group. The administration schedule of IT MTX may be an important risk factor.