(50) Effect of Low-Dose Aspirin on The Primary Prevention of Colorectal Cancer in Patients with Type 2 Diabetes Taking Metformin

Saturday, August 27, 2022

8:00 AM – 6:00 PM CEST

Location: Hall C

Publication Number: 724

Presenting Author(s)

Jessica Shami
– University of Hong Kong, Hong Kong, Hong Kong

Co-Author(s)

Vincent KC Yan
– Centre for Safe Medication Practice and Research, Department of Pharmacology and Pharmacy, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China, Hong Kong
Yue WEI
– The University of Hong Kong, The University of Hong Kong, Hong Kong, Hong Kong
Ian Wong
– Professor, Centre for Safe Medication Practice and Research, Department of Pharmacology and Pharmacy, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China, Hong Kong
Esther W Chan
– Centre for Safe Medication Practice and Research, Department of Pharmacology and Pharmacy, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China, Hong Kong

Background: Low-dose aspirin has been associated with a reduced risk of colorectal cancer (CRC). While metformin has been suspected to lower the risk of some types of cancer including CRC. Whether there is an additional protective effect with their concurrent use in adults with type 2 diabetes mellitus (T2DM) is unclear.

Objectives: To evaluate the association between low-dose aspirin and the risk of CRC and overall cancer in patients with T2DM taking metformin.

Methods: A multiple-database new-user cohort study of patients with T2DM taking metformin between January 1, 2007 and December 31, 2010 (Clinical Data Analysis and Reporting System [CDARS], Hong Kong) and January 1, 2007 and December 31, 2016 (The Health Improvement Network [THIN], UK). The primary outcome was incident CRC identified using International Classification of Diseases, 9th revision codes in CDARS and Read codes in THIN. Patients were followed from index date of prescription until the earliest occurrence of an outcome of interest, an incident diagnosis of any cancer, death, or until December 31 2019. Concurrent users of low-dose aspirin and metformin (exposure group) were propensity-score matched to metformin only users (control group) at a 1:1 ratio to minimize baseline differences. Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI). Pooled hazard ratio was estimated using a random effect model.

Results: After propensity-score matching, 57,534 patients (16,276 CDARS and 41,258 THIN) with T2DM taking metformin were included in the analysis. The median (IQR) follow-up was 9.3 (6.5-10.7) years in CDARS and 3.2 (1.1-5.8) years in THIN. The concurrent use of low-dose aspirin and metformin was not associated with a lower risk of CRC compared to metformin only in CDARS (HR = 0.83, 95% CI = 0.67-1.04), THIN (HR = 0.99, 95% CI = 0.75-1.29) and in the pooled results (HR = 0.89, 95% CI 0.75-1.05, I2 = 0%).

Conclusions: Concurrent use of low-dose aspirin and metformin was not associated with a lower risk of CRC compared to metformin use in patients with T2DM. Our study does not support the routine use of low-dose aspirin for CRC prevention in individuals with T2DM taking metformin.