September 12, 2012
1 min read

Metformin not associated with a decreased risk for lung cancer in patients with type 2 diabetes

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Previous observational studies have linked metformin with a decreased risk for lung cancer in patients with type 2 diabetes. After further examination, researchers have found that metformin is not related to a decreased risk for lung cancer in this patient population, and past findings could be biased or due to chance.

The latest study, conducted by Brielan B. Smiechowski, MSc, from the Centre for Clinical Epidemiology, Lady Davis Institute, Jewish General Hospital in Montreal, Quebec, and colleagues included a cohort of 115,923 patients (55.2% men; mean age 64) who were new users of oral hypoglycemic agents (OHAs). Patients were obtained using the U.K. General Practice Research Database (GPRD).

According to the researchers, a nested case-control analysis was completed where patients with lung cancer at follow-up were matched with up to 10 control patients. Additional models were used to estimate adjusted rates and confounders, including smoking.

At the start of the cohort study, median HbA1c levels were 8.2%, and 67.4% of patients received metformin alone, 29.6% received sulfonylureas alone, 1.3% received other OHAs alone, and 1.7% were taking a combination of at least two OHAs, researchers wrote.

After a mean follow-up of 5.6 years, researchers found 1,061 patients were diagnosed with lung cancer (RR=2.0; 95% CI, 1.9-2.1).

Baseline characteristics, including duration of diabetes before cohort entry, HbA1c, BMI and NSAID ever-use, were similar among cases and controls.

“As expected, the prevalence of smoking was higher in case subjects than in matched control subjects (85.2% vs. 60.0%, respectively). Furthermore, case subjects were more likely than control subjects to have had a history of chronic obstructive pulmonary disease, to have a history of asthma, to have used alcohol excessively, and to have ever used aspirin and statins,” the researchers wrote.

Overall, they reported that the use of metformin was not associated with a decreased rate of lung cancer among patients with type 2 diabetes (adjusted RR = 0.94; 95% CI, 0.76-1.17). Additionally, secondary analyses revealed that there was no dose-response in the number of metformin prescriptions received, cumulative duration and cumulative dose, and all adjusted RRs were near null, they wrote.

The researchers suggest further studies to examine metformin as an indicated therapy for oncology.

Disclosure: The researchers report no relevant financial disclosures.