Aim: To investigate the incidence, patterns and latency of secondary primary cancers (SPCs) among individuals diagnosed with childhood cancer in Australia, up to 40 years after initial diagnosis.
Methods: This retrospective cohort study used de-identified records from the Australian Childhood Cancer Registry (ACCR). Individuals diagnosed with a first primary cancer before 15 years of age between 1 January 1983 and 31 December 2022, were followed for SPCs to 31 December 2023. Information on SPC was obtained by matching with the Australian Cancer Database, which records all primary malignant cancers diagnosed in Australian residents. Patterns and number of SPCs were described, and standardized incidence ratios (SIRs) were used to compare relative risk by type of first and second cancer. Trends over time and latency between first and second primary cancer were assessed descriptively.
Results: Analyses will be finalised in September with the latest ACCR extract. Preliminary analyses using data between 1983-2022 show that among 26,039 children diagnosed with cancer, 747 individuals developed at least one SPC, with 30% diagnosed with second cancer before age 15 years, 45% at 15-29 years, and 24% at 30-49 years. Childhood cancer survivors had increased risk of SPCs than the general population. Risks and latency of SPC diagnosis varied by first cancer type. Among 172 children diagnosed with acute lymphoid leukaemia who developed a SPC, the most common were thyroid carcinoma (24%, 6-24 years after primary), AML (14%, 2 months -12 years after primary) and astrocytoma (12%, 6-27 years after primary). Among 52 children diagnosed with intracranial and intraspinal embryonal tumours who developed a SPC, 42% were diagnosed with a thyroid carcinoma 4-32 years after primary.
Conclusion: Detailed description on subsequent primary cancers among childhood cancer survivors during childhood and adulthood are important for ongoing screening and monitoring for timely detection of subsequent tumours.