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Metformin use and survival after colorectal cancer: A population-based cohort study


Mc Menamin Ú, Murray L, Hughes C, Cardwell C

Departments / Institutions

Centre for Public Health, Queen’s University Belfast

Publication Date

Autumn 2015


Preclinical evidence suggests that metformin could delay cancer progression. Previous epidemiological studies however have been limited by small sample sizes and certain time-related biases. This study aimed to investigate whether colorectal cancer patients with type 2 diabetes who were exposed to metformin had reduced cancer-specific mortality.


We conducted a retrospective cohort study of 1,197 colorectal cancer patients diagnosed from 1998 to 2009
(identified from English cancer registries) with type 2 diabetes (based upon Clinical Practice Research Datalink, CPRD, prescription and diagnosis records). In this cohort 382 colorectal cancer-specific deaths occurred up to 2012 from the Office of National Statistics (ONS) mortality data. Metformin use was identified from CPRD prescriptions. Using time-dependent Cox regression models, unadjusted and adjusted hazard ratios (HR) and 95% CIs were calculated for the association between postdiagnostic exposure to metformin and colorectal cancer-specific mortality.


Overall, there was no evidence of an association between metformin use and cancer-specific death before or after adjustment for potential confounders (adjusted HR 1.06, 95% CI 0.80, 1.40). In addition, after adjustment for confounders, there was also no evidence of associations between other diabetic medications and cancer-specific mortality including sulfonylureas (HR 1.14, 95% CI 0.86, 1.51), insulin use (HR 1.35, 95% CI 0.95, 1.93) or other anti-diabetic medications including thiazolidinediones (HR 0.73, 95% CI 0.46, 1.14). Similar associations were observed by duration of use and for all-cause mortality.


This population-based study, the largest to date, does not support a protective association between metformin and survival in colorectal cancer patients.

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