Health system leaders and policymakers attended a Cancer Research UK (CRUK) event to get an insight into the UK National Screening Committee (UK NSC) position on the use of surrogate outcomes in cancer screening trials.
The CRUK Early Diagnosis Event Series session raised awareness of the UK National Screening Committee’s (UK NSC) newly published position statement on surrogate outcomes in cancer screening trials.
The event was chaired by UK NSC Chair Prof Sir Mike Richards and speakers included Prof Anne Mackie (UK NSC Director of Screening), Dr Sarah Batson (Assistant Professor at University of Warwick), Dr Tasmin Sommerfield (Scottish Director of Screening), and Dr Lisa Douet (National Institute for Health and Care Research (NIHR) Scientific Advisor).
Read the CRUK summary report of the event: Understanding surrogate outcomes in cancer screening trials: implications for screening policy and practice.
Why alternative indicators of screening effectiveness would be helpfulThe UK NSC only recommends a screening programme if evidence shows that its benefits would outweigh any harms.
The gold-standard measure of effectiveness for any cancer screening programme is achieving a reduction in deaths from that cancer. However, it can take many years or even decades to collect the cancer-specific mortality data required from large trials.
Academics have therefore been looking for alternative measurements or indicators of screening effectiveness. These outcomes act as a ‘surrogate’ for the desired outcome of mortality reduction before that long-term data is available.
To date, the most promising surrogate outcomes proposed for cancer screening trials have included:
a fall in the number or proportion of cancers detected at a later stage a rise in the number or proportion of cancers detected at an earlier stage a rise in cancer detection ratesHowever, the evidence is not yet strong enough for surrogate outcomes to replace cancer mortality as the definitive measure of the overall benefit of screening.
This is because finding more cancers at an earlier stage does not necessarily mean fewer people will die from cancer. Additional cancers detected may be very slow-growing or may never cause harm during a person's lifetime. In addition, what is considered a ‘late-stage’ cancer varies between cancer types, and the link between surrogate outcomes and cancer mortality is not the same for all cancers.
Implications and next stepsThe CRUK event provided an overview of the UK NSC’s position statement on surrogate outcomes and explored its implications for health system leaders and policymakers.
Overall, the session reinforced the committee’s view that surrogate outcomes can inform screening research, evaluation and policy discussions, but cannot yet replace cancer-specific mortality as the main measure of cancer screening benefit.
Attendees heard that while a reduction in late-stage disease is encouraging as a surrogate outcome, it is not yet sufficient to demonstrate the benefit of screening.
Participants explored how health systems can try to make evidence-informed decisions in the face of uncertainty. They also discussed the use of in-service evaluations (ISEs) as an important approach to generating evidence in real-world settings.
The summary report concludes with actions and next steps for policy makers and researchers to consider when shaping the future of cancer screening.
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seen at 14:35, 1 October in UK National Screening Committee.