Metformin use reduces risk of oesophageal squamous cell carcinoma

Use of metformin provides a protective benefit against the development of oesophageal squamous cell carcinoma (ESCC), a recent study has shown.

This nationwide population-based prospective cohort study conducted from 2005 through 2015 involved a total of 8.4 million participants and identified 411,603 (5 percent) metformin users. The authors compared metformin users with 10 times as many frequency nonusers (4,116,030) matched by age and sex.

Metformin use was treated as a time-varying variable. Hazard ratios (HR) with 95 percent confidence intervals (CI) for ESCC were calculated using multivariable cause-specific proportional hazards model, adjusted for age, sex, calendar year, residence area, tobacco smoking, alcohol overconsumption and use of nonsteroidal anti-inflammatory drugs or statins.

The incidence rate of ESCC was lower among metformin users compared with nonusers (3.5 vs 5.3 per 100,000 person-years). Overall, metformin users had a lower risk of ESCC than nonusers (HR, 0.68, 95 percent CI, 0.54–0.85). This decrease in risk was more noticeable among new users (HR, 0.44, 95 percent CI, 0.28–0.64) and older participants (aged 60–69 years; HR, 0.45, 95 percent CI, 0.31–0.66).

In contrast, another study with <10 years of follow-up suggested that metformin use may not prevent gastric adenocarcinoma. [Br J Cancer 2019;121:877-882]

“Oesophageal cancer is a highly fatal malignant neoplasm, with two aetiologically different histological types,” the authors said. “A large prospective study is expected to elucidate the specific risk of the 90-percent subtype of oesophageal cancer, ESCC, with metformin therapy.”