Real-world evidence for the postmarket surveillance of cancer medicines: opportunities and challenges using Australia's population-based cancer registries.

Spending on cancer medicines has increased rapidly worldwide, driven by the introduction of immunotherapy and targeted therapy. Australia exemplifies this trend, with cancer medicines representing one of the largest and fastest-growing areas of expenditure for Australia's public medicines funder, the Pharmaceutical Benefits Scheme. While this growth reflects therapeutic innovation and expanded clinical use, it has intensified concerns around the real-world safety, effectiveness, and value of novel therapies once adopted into routine care. Randomised clinical trials remain essential for regulatory approval but often provide limited insight into outcomes in broader, more heterogeneous populations, particularly as many therapies enter practice via accelerated pathways based on surrogate endpoints. Population-based cancer registries offer an important resource for postmarket surveillance when linked with national administrative datasets such as dispensing and hospitalisations records. However, limitations in registries' timeliness, disease stage ascertainment, biomarker and genomic data capture, and information on recurrence and progression constrain their current utility. This perspective examines the Australian population-based cancer registry landscape, highlighting its strengths, untapped potential, and critical gaps. We outline priority enhancements required to realise a robust, whole-of-population cancer medicine surveillance system that can inform clinical practice, policy, and sustainable health care decision making.