Estimating overall survival in people receiving PBS-listed cancer medicines in Australian clinical practice

Page last updated: 18 August 2023


Cost-effectiveness analyses underpin decisions to subsidise health technologies in many health jurisdictions globally and quantifying the benefits of new treatments, such as estimating overall survival (OS) associated with treatment, is a key component of these analyses. OS is a commonly reported metric that measures the period of time from a specific start point (often cancer diagnosis or treatment initiation) until the date of death or the end of follow-up for a cohort. The advantage of OS as a clinical trial outcome is that it represents an unequivocal endpoint that can be assessed with 100% accuracy both for its occurrence and timing, provided the number of patients with incomplete follow-up times is not substantial. Median OS—the amount of time by which 50% of the cohort have died and, necessarily, 50% survive beyond—with a corresponding 95% confidence interval or interquartile range is often reported to characterise survival in patients treated for cancer.

Sponsor submissions for health technology reimbursement typically rely on estimates derived from clinical trials. However, these estimates often differ substantially from real-world OS estimates. These differences have implications for the ongoing cost-effectiveness of these medicines or technologies post-subsidy.

In September 2021, the Department of Health and Aged Care contracted the Medicines Intelligence Centre for Research Excellence (MI-CRE) to complete a two-stage research project to:

‘Investigate how OS estimated in patients taking certain Pharmaceutical Benefits Scheme (PBS)-listed cancer medicines in Australia compares to the OS of patients taking the same medicines reported in the pivotal trials included in sponsor submissions to the Pharmaceutical Benefits Advisory Committee (PBAC).’

The first stage of this project was to develop a comprehensive research protocol and methodology to conduct a similar study to Green et al. (2021)1 using PBS data initially, and ultimately linked health data available in Australia. The second stage of the project was to conduct the analysis in a pilot medicine and review the results for applicability and comparability with the pivotal trial results.

The Department received the final report of the Protocol in October 2022. The Protocol details the MI-CRE’s advice to the PBAC, focusing on medicines indicated for advanced solid cancers, i.e. metastatic and locally advanced indications without curative intent. The Protocol is provided in DOCX and PDF format below. Committee-in-confidence information in the Protocol has been redacted.

[1] Green AK, Curry M, Trivedi N, Bach PB, Mailankody S. Assessment of Outcomes Associated With the Use of Newly Approved Oncology Drugs in Medicare Beneficiaries. JAMA Netw Open. 2021;4(2): e210030. doi:10.1001/jamanetworkopen.2021.0030.

PBAC consideration of the Protocol

The Protocol was provided to the PBAC for consideration in May 2023.

The PBAC advised that overall, the Protocol was informing regarding the methods that are considered ‘best-practice’ when using PBS data to derive estimates of the survival outcomes attributed to specific cancer medicines. The PBAC considered that the methods detailed in the Protocol may help inform other health technology assessment (HTA) research by contributing to the robust analysis of OS using PBS data linked to other clinical data in the future.

The PBAC was supportive of further exploration into how this research could be extended to other cancer medicines and/or different medicine classes.

The PBAC Minutes for this item are available below. Parts of the PBAC Minutes have been redacted due to ‘committee-in-confidence’ information.