Second neoplasms after treatment of childhood cancer in Slovenia. 
The number of long time survivors of childhood cancer treatment is constantly increasing over the last decades as a result of advances in diagnosis and treatment.  The occurrence of second neoplasms is one of most serious late effects observed in cancer survivors.  The risk of secondary neoplasm was studied in a cohort of 1,577 patients treated for childhood cancer registered in the Cancer Registry of Slovenia (CRS) between 1961 and 2000.  The time at risk was defined from the date of diagnosis of first malignancy to the time of death or the end of the study.  The most frequent primary malignancies were: acute leukemia 28.5%, central nervous system (CNS) tumors 21.3%, and lymphomas 16.6%.  Median observation time was 7.8 years.  Forty-eight patients developed second neoplasms.  CNS tumors, acute leukemias, and thyroid carcinoma were most frequent second neoplasms.  The cumulative risk for second neoplasm in the entire cohort was 0.06% at 5 years, 5.1% at 15 years, and 12.6% at 25 years after diagnosis of first cancer.  The overall survival after second neoplasm was 65% 10 years after the diagnosis of second neoplasm.  Patients after treatment of childhood cancer are at special risk for subsequent neoplasms and long-term follow-up is mandatory.