Lung cancer risk may decrease in diabetic non-smokers through metformin

Metformin, a drug used to treat type 2 diabetes, may lower the risk of lung cancer in non-smokers with diabetes, a study suggests.
Researcher Lori Sakoda and colleagues at the Kaiser Permanente Division of Research in Oakland, California, studied metformin to see if it could prevent cancer.
They conducted a retrospective cohort study of 47,351 patients with diabetes aged 40 or older between 1994 and 1996, and all completed a health-related survey.
Information on their diabetes medication was collected from pharmacy records, with 46 per cent of the participants filling two or more prescriptions of metformin within a six-month period.
747 participants were diagnosed with lung cancer during 15 years of follow-up. 80 were non-smokers and 203 were current smokers.
The use of metformin was not associated with an overall lower lung cancer risk, but the reduced risk was 43 per cent among non-smoker diabetics, with the risk appearing to continually decrease with longer use.
There was a 52 per cent reduced risk of lung cancer for non-smokers using metformin for five years or over, but this was not a statistically significant finding.
“Metformin use was not associated with lung cancer risk when we looked at all patients with diabetes. However, our results suggest that risk might differ by smoking history, with metformin decreasing risk among non-smokers and increasing risk among current smokers,” concluded Sakoda.