Metformin Use Linked to Reduced Blood Cancer Risk, Study Finds

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A new study from Denmark has found that people taking the type 2 diabetes drug metformin are less likely to develop a myeloproliferative neoplasm (MPN) - a rare type of blood cancer that can develop into acute leukemia.

The study is published in Blood Advances.

Metformin: An old drug up to new tricks?

Metformin is a drug that has been used for decades to help treat and manage type 2 diabetes. It works by boosting the effects of insulin, the hormone that controls blood sugar.

However, numerous studies have found that the benefits of metformin may extend beyond diabetes, for conditions such as gum disease, muscle atrophy and long COVID. There is also evidence that metformin may help to promote healthy aging.

Furthermore, metformin may also impact cancer development; a meta-analysis of 166 studies found associations between metformin use and reduced risk of developing gastrointestinal, breast and urologic cancers.

"Our team was interested in understanding what other effects we see with commonly prescribed treatments like metformin," explained the study's senior author, Dr. Anne Stidsholt Roug, chief physician at Aarhus University Hospital and clinical associate professor at Aalborg University Hospital in Denmark.

Roug and colleagues investigated the possibility of an association between metformin use and reduced risk of MPN. These are a rare type of blood cancer in which the bone marrow overproduces blood cells - red and white blood cells as well as platelets - potentially leading to bleeding problems, organ damage and risks of stroke or heart attack.

"The anti-inflammatory effect of metformin interested us, as MPNs are very inflammatory diseases," Roug added. "This is the first study to investigate the association between metformin use and risk of MPN."

Association with reduced blood cancer risk

The researchers utilized data from Danish health registries to compare 3,816 cases of MPN against over 19,000 controls who did not have MPN.

They found that 8.2% of the non-MPN control group had taken metformin, compared to 7% of people in the MPN group. Additionally, 2% of the controls had taken metformin for longer than 5 years, compared to 1.1% in the MPN group. The protective effect of metformin was still observed in all MPN subtypes after adjusting for potential confounding factors.

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"We were surprised by the magnitude of the association we saw in the data," explained Dr. Daniel Tuyet Kristensen, a PhD student at Aalborg University Hospital and the lead author of the study. "We saw the strongest effect in people who had taken metformin for more than five years as compared to those who had taken the treatment for less than a year."

Further investigation needed

This makes clinical sense, Kristensen explains, as MPNs - like other cancers - develop over many years. However, the study was limited by its registry-based retrospective design and by being unable to account for lifestyle factors that influence cancer risk such as smoking, obesity and diet.

Roug noted that while the study couldn't determine the exact mechanisms underpinning the potential protective effect of metformin against MPN, additional studies may be able to delve deeper. Roug and the team are now aiming to identify other similar trends in MPN and acute leukemia in population-level data.

Reference: Kristensen DT, Øvlisen AK, Jakobsen LHK, et al. Metformin use and risk of myeloproliferative neoplasms - a Danish population-based case-control study. Blood Advances. 2024. doi: 10.1182/bloodadvances.2023012266

This article is a rework of a press release issued by the American Society of Hematology. Material has been edited for length and content.