Subsequent neoplasms in childhood cancer survivors.

Objectives: The aim of the study was to characterize subsequent neoplasm (SN) (malignant (SMN), benign (BSNs), and non-melanoma skin cancer (NMSC)) treated previously for a childhood solid malignant tumor at the Department of Pediatric Hematology and Oncology, Motol University Hospital, Prague. Method: We evaluated a cohort of 4059 childhood cancer survivors treated between 1975 and 2018. Results: From 4059 survivors, 170 (4.3 %) developed at least one SMN - 193 SMNs in 170 survivors, 21 of them (0.5 % of all survivors) had two or more SMNs and 34 of them (0.8 %) had one SMN and one or more BSNs. Mortality for an SMN was 38.2 % i.e. 1.6 % of all survivors. The most frequent SMNs were thyroid carcinoma (37, 19.2 %), tumors of the central nervous system (25, 13.0 %), soft tissue sarcoma (23, 11.9 %), breast carcinoma (19, 9.8 %), and leukemia (11, 5.7 %). Genetic syndromes were present in 25 patients with SMNs (14.7 %) and in 16 patients with only BSNs (13.4 %). SMNs usually developed in second decade or later after finishing of therapy. We observed some not well known risk factors of SNs e.g. spinal irradiation or(131-)I metaiodobenzylguanidine radiotherapy in 2 cases of secondary thyroid cancer, cyclophosphamide therapy in all 8 cases of secondary urinary bladder sarcoma or 4 from 7 SNMSC developed SMN. Conclusions: We confirmed data from previous studies of SNs and observed some not so well known risk factors. Our results and the literature show that the incidence of SMNs is 3-10 % of survivors and is associated with high mortality.