The financial impact of cancer medicines on health systems is not well known. We describe temporal trends in expenditure on cancer medicines within the single-payer health system of Ontario, Canada, and the extent of clinical benefit these treatments offer.

In this cross-sectional study, we identified cancer medicines and expenditures from formularies and costing databases (the New Drug Funding Program, Ontario Drug Benefit Program, and The High-Cost Therapy Funding Program) during 10 consecutive years (April 1, 2012, to March 31, 2022) in Ontario, Canada. For intravenous medicines, we applied the European Society for Medical Oncology Magnitude of Clinical Benefit Scale (ESMO-MCBS) to identify expenditures associated with substantial clinical benefit. We also identified treatments associated with improved overall survival or quality of life.

69 intravenous and 98 oral or injectable medicines were funded during 2012–22. Annual expenditure on cancer medicines increased by approximately 15% per year during 2012–22; the increase was more rapid in the most recent 4 years. Total expenditure on cancer medicines in the 2021–22 financial year was CA$1·7 billion. Immune checkpoint inhibitors were the single biggest expense by class ($284 million), representing 17% of the entire cancer medicine annual budget. Drugs with the highest individual costs were lenalidomide ($178 million) and pembrolizumab ($163 million), each accounting for around 10% of the entire budget. 29 (76%) of 38 indications eligible for ESMO-MCBS scoring met the threshold for substantial clinical benefit. Eight (21%) indications had no randomised trial evidence of improved overall survival, and only four (11%) were associated with improved QOL. $346 million (67% of the expenditure on intravenous cancer medicines) was spent on drugs that improved median overall survival by more than 6 months, $82 million (16%) was spent on medicines with overall survival gains of 3–6 months, and $32 million (6%) was spent on medicines with overall survival gains of less than 3 months. $53 million (10%) was spent on medicines with no established improvement in overall survival.

Costs of cancer medicines to the Canadian health system are increasing rapidly. Most funded indications met thresholds for substantial clinical benefit and two-thirds of the expenditure were for medicines that improve survival by more than 6 months. Whether this cost trajectory can be maintained in a sustainable, equitable, high-quality health system is unclear. Efforts are needed to ensure the price of medicines with substantial benefit is affordable and funding of treatments with very modest benefit might need to be re-assessed, particularly when alternative supportive and palliative therapies are available.

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