Background/Objectives: To describe the incidence and outcomes of childhood renal malignancies in Australia using whole‐country population data from the Australian Childhood Cancer Registry (ACCR). To describe the occurrence of second primary malignancy (SPM) in children treated for renal cancers.

Design/Methods: All children (0‐14 years) diagnosed with renal malignancies from 1983‐2014 inclusive were identified in the ACCR. Demographic, tumour characteristic, incidence, mortality and treatment data were extracted from the Registry. Cause‐specific (CS) and event‐free (EFS) survival up to 20 years from diagnosis were estimated using the cohort method. Adjusted excess mortality hazard ratios (HR) were calculated using a multivariate flexible parametric survival model. Cumulative incidence, standardised incidence ratios (SIR), absolute excess risk (AER), and mortality relating to SPMs were calculated.

Results: There were 1,007 children diagnosed with renal malignancies between 1983‐2014 (91% nephroblastoma), generating an annual age‐standardised incidence rate of 8 per million children. This incidence did not change over the study period. Cause‐specific survival was 89% and 88% at 5 and 20 years, respectively. Five‐year EFS was 82%. Five‐year CS did not change over the study period. Five‐year CS was highest in nephroblastoma (91%) and poorest for rhabdoid renal tumours (36%, HR=8.2 in comparison to nephroblastoma, p<0.001). All deaths from rhabdoid tumours occurred within 12 months of diagnosis. Of patients achieving remission, 15% relapsed and subsequent 5‐year CS was 49%. Ten children were diagnosed with a SPM (cumulative incidence at 20 years = 2.8%), giving a SIR of 3.05, AER 5.1/10,000 person‐years. Half of those with a SPM died within 5 years of second diagnosis.

Conclusions: Children treated for renal malignancies in Australia have excellent long‐term survival, unchanged since 1983. SPMs are uncommon following treatment for childhood renal cancer, but carry a poor prognosis. Relapse carries a similarly poor prognosis. These data are comparable to registry outcomes in similarly developed nations.