Diabetes drug metformin may cut breast cancer risk in older women

June 11, 2012 By Barbara Bronson Gray, HealthDay Reporter
Diabetes drug metformin may cut breast cancer risk in older women
But evidence isn't strong enough yet to change clinical practice, experts note.

(HealthDay) -- A widely prescribed drug, metformin, may lower the risk of invasive breast cancer in postmenopausal women with diabetes, a new study indicates.

The research, published online June 11 in the Journal of Clinical Oncology, echoes other recent studies that have suggested the may help cut the chances of prostate, pancreatic, liver and , as well as certain forms of melanoma.

The researchers found that the incidence of was 25 percent lower in women with diabetes who were taking than it was in women who weren't taking the .

Approximately 25.8 million people in the United States have diabetes, according to the U.S. . Between 90 percent and 95 percent of these cases are , in which the body's ability to make and use insulin deteriorates.

"Type 2 diabetes is a disease of ," said study co-author Dr. Rowan Chlebowski, a medical oncologist with the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, in Torrance, Calif.

Insulin is a hormone that helps regulate the level of glucose (sugar) in the body. With type 2 diabetes, the body manufactures larger quantities of insulin to maintain normal levels of glucose in the blood.

Metformin, commonly used to treat type 2 diabetes, increases and improves the control of blood sugar. "It makes the insulin you have more effective," Chlebowski explained. The drug, approved in the United Kingdom in 1958 and in Canada in 1972, was introduced in the United States in 1994.

The new research looked at relationships among diabetes, metformin use and breast cancer among over 68,000 women between 50 and 79 years old in the national Women's Health Initiative project. In this group, 3,401 had diabetes and 3,273 invasive breast cancers were diagnosed during the study.

Because of the design of the Women's Health Initiative trials, detailed information was available for this large and diverse population in many areas, including breast cancer risk factors, baseline mammograms, clinical breast exams and verification of breast cancers when they occurred. Researchers were also able to know which participants had diabetes -- along with their use of diabetes medication.

The trials excluded women who had already had breast cancer. Women who had developed diabetes before adulthood (suggesting they were type 1 diabetics) were also excluded from the study.

How can a drug that treats people with high blood sugar play a role in reducing breast ? Chlebowski suggested that metformin "may inhibit the master regulator of the cell, 'mTOR,' changing critical pathways involved in cancer."

The mTOR pathway is affected by a wide range of cellular signals, including growth factors, hormones such as insulin, nutrients including glucose and amino acids, cellular energy levels and stress. A key cell pathway associated with mTOR is critically involved in cell reproduction and survival.

Chlebowski and other experts cautioned against looking to metformin as a cancer prevention drug just yet.

"It's too soon to change clinical practice," said Jennifer Ligibel, a medical oncologist in the Women's Cancer Program at the Dana-Farber Cancer Institute in Boston. "While a number of other studies have suggested metformin has a role in preventing breast cancer and its recurrence, I would not recommend women take metformin for breast cancer prevention based on the data we have now."

As to the question of whether metformin could ever be used more broadly beyond diabetic patients to reduce the risk of breast cancer, Chlebowski said the answer is unclear and more studies are necessary to further analyze the linkage.

While the study uncovered an association between metformin use and lower risk in diabetic postmenopausal women, it did not prove a cause-and-effect relationship.

The U.S. Food and Drug Administration has issued warnings about metformin in recent years. It requires product inserts for physicians and patients to say that the drug has been associated with increased cardiovascular risks, including heart attack and stroke, and lactic acidosis, which causes fatigue, muscle pain, difficulty breathing and other symptoms. The FDA also stipulates that the drug literature include a warning that the drug should only be used by patients with type 2 who cannot control their blood sugar with lifestyle or other medications.

Explore further: Metformin may have dual effect in breast cancer

More information: The U.S. National Library of Medicine has more on type 2 diabetes.


Related Stories

Metformin may have dual effect in breast cancer

May 9, 2012
(HealthDay) -- For women without diabetes and with operable breast cancer, administration of metformin prior to surgery does not significantly affect the proliferative marker Ki-67 overall, but drug effects are observed according ...

Diabetes and obesity increase risk for breast cancer development

December 7, 2011
Having diabetes or being obese after age 60 significantly increases the risk for developing breast cancer, a Swedish study has revealed. Data also showed that high blood lipids were less common in patients when diagnosed ...

Diabetes drug metformin shows promise in reducing risk of cancer

November 23, 2011
An inexpensive drug that treats Type-2 diabetes has been shown to prevent a number of natural and man-made chemicals from stimulating the growth of breast cancer cells, according to a newly published study by a Michigan State ...

Recommended for you

How cancer metastasis happens: Researchers reveal a key mechanism

January 18, 2018
Cancer metastasis, the migration of cells from a primary tumor to form distant tumors in the body, can be triggered by a chronic leakage of DNA within tumor cells, according to a team led by Weill Cornell Medicine and Memorial ...

Modular gene enhancer promotes leukemia and regulates effectiveness of chemotherapy

January 18, 2018
Every day, billions of new blood cells are generated in the bone marrow. The gene Myc is known to play an important role in this process, and is also known to play a role in cancer. Scientists from the German Cancer Research ...

These foods may up your odds for colon cancer

January 18, 2018
(HealthDay)—Chowing down on red meat, white bread and sugar-laden drinks might increase your long-term risk of colon cancer, a new study suggests.

The pill lowers ovarian cancer risk, even for smokers

January 18, 2018
(HealthDay)—It's known that use of the birth control pill is tied to lower odds for ovarian cancer, but new research shows the benefit extends to smokers or women who are obese.

Researchers develop swallowable test to detect pre-cancerous Barrett's esophagus

January 17, 2018
Investigators at Case Western Reserve University School of Medicine and University Hospitals Cleveland Medical Center have developed a simple, swallowable test for early detection of Barrett's esophagus that offers promise ...

Scientists zoom in to watch DNA code being read

January 17, 2018
Scientists have unveiled incredible images of how the DNA code is read and interpreted—revealing new detail about one of the fundamental processes of life.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.