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Can metformin prevent cancer relative to sulfonylureas? A target trial emulation accounting for competing risks and
Shenbo Xu1, Bang Zheng1, Bowen Su1
1Institute for Data, Systems, and Society, Massachusetts Institute of Technology, Cambridge, MA 02142, United States.
Abstract:
There is mounting interest in the possibility that metformin, indicated for glycemic control in type 2 diabetes, has a range of additional beneficial effects. Randomized trials have shown that metformin prevents adverse cardiovascular events, and metformin use has also been associated with reduced cognitive decline and cancer incidence. In this paper, we dig more deeply into whether metformin prevents cancer by emulating target randomized trials comparing metformin to sulfonylureas as first-line diabetes therapy using data from the Clinical Practice Research Datalink, a UK primary-care database (1987-2018). We included 93 353 individuals with diabetes, no prior cancer diagnosis, no chronic kidney disease, and no prior diabetes therapy who initiated use of metformin (n = 79 489) or a sulfonylurea (n = 13 864). In our cohort, the estimated overlap-weighted additive separable direct effect of metformin compared with sulfonylureas on cancer risk at 6 years was -1 percentage point (95% CI, -2.2 to 0.1), which is consistent with metformin's providing no direct protection against cancer incidence or substantial protection. The analysis faced 2 methodological challenges: (1) poor overlap and (2) precancer death as a competing risk. To address these issues while minimizing nuisance model misspecification, we develop and apply double/debiased machine learning estimators of overlap-weighted separable effects in addition to more traditional effect estimates. This article is part of a Special Collection on Pharmacoepidemiology.
Insights
Metformin, a type 2 diabetes drug, was studied for cancer prevention. The research found no significant direct protection against cancer incidence when compared to sulfonylureas, suggesting limited benefit for cancer risk reduction.
Area of Science:
- Pharmacoepidemiology
- Diabetes Mellitus Research
- Oncology
Background:
- Metformin is a primary treatment for type 2 diabetes.
- Emerging evidence suggests metformin may offer benefits beyond glycemic control, including cardiovascular protection, reduced cognitive decline, and lower cancer incidence.
- The potential anti-cancer effects of metformin warrant further investigation.
Purpose of the Study:
- To investigate whether metformin prevents cancer by emulating target randomized trials.
- To compare the cancer risk associated with metformin versus sulfonylureas as first-line diabetes therapy.
- To address methodological challenges in pharmacoepidemiological studies, including poor data overlap and competing risks.
Main Methods:
- Utilized data from the Clinical Practice Research Datalink (UK primary-care database, 1987-2018).
- Included 93,353 individuals with diabetes, no prior cancer, no chronic kidney disease, and no prior diabetes therapy.
- Emulated target randomized trials comparing metformin (n=79,489) to sulfonylureas (n=13,864) using double/debiased machine learning estimators for overlap-weighted separable effects.
Main Results:
- The estimated effect of metformin compared to sulfonylureas on cancer risk at 6 years was -1 percentage point (95% CI, -2.2 to 0.1).
- This result is consistent with metformin providing no direct protection or only substantial protection against cancer incidence.
- Methodological challenges included poor overlap and precancer death as a competing risk, addressed by advanced statistical methods.
Conclusions:
- Metformin, when compared to sulfonylureas as a first-line diabetes therapy, did not demonstrate a significant direct protective effect against cancer incidence in this cohort.
- The findings suggest that the potential benefits of metformin may not extend to direct cancer prevention.
- Advanced statistical methods were employed to overcome limitations in observational data for pharmacoepidemiological research.
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