Second Malignant Neoplasms in Childhood Cancer Survivors Treated in a Tertiary Paediatric Oncology Centre

: One of the most feared complications of childhood cancer treatment is second malignant neoplasms (SMNs). This study evaluates the incidence, risk factors and outcomes of SMNs in a tertiary paediatric oncology centre in Singapore. : A retrospective review was conducted on patients diagnosed with childhood cancer under age 21 and treated at the National University Hospital, Singapore, from January 1990 to 15 April 2012. Case records of patients with SMNs were reviewed. : We identified 1124 cases of childhood cancers with a median follow-up of 3.49 (0 to 24.06) years. The most common primary malignancies were leukaemia (47.1%), central nervous system tumours (11.7%) and lymphoma (9.8%). Fifteen cases developed SMNs, most commonly acute myeloid leukaemia/myelodysplastic syndrome (n = 7). Median interval between the first and second malignancy was 3.41 (0.24 to 18.30) years. Overall 20-year cumulative incidence of SMNs was 5.3% (95% CI, 0.2% to 10.4%). The 15-year cumulative incidence of SMNs following acute lymphoblastic leukaemia was 4.4% (95% CI, 0% to 8.9%), significantly lower than the risk after osteosarcoma of 14.2% (95% CI, 0.7% to 27.7%) within 5 years (