Blood Pressure Medication Ups Breast Cancer Risk

Certain medications used to lower blood pressure may be increasing the risk of breast cancer, a new study reported.

Researchers found that women taking calcium channel blockers for about a decade are twice as likely to be diagnosed with breast cancer when compared to those who don't take the drug.

About 678 million prescriptions were filled for high blood pressure drugs in 2010, making them the most-prescribed drugs in the U.S, the study said.

Some 67 million or 1 out of every 3 American adults has high blood pressure and about 36 million don't have it under control, according to data from Centers for Disease Control and prevention (CDC) report .

The study results aren't conclusive enough to change the way the drugs are prescribed though.

"While this is an intriguing finding, much more work still needs to be done," While we appreciate that these results may cause concern for women currently using these medications, we do not think that they should change current clinical practice because they require confirmation and because of the importance of managing hypertension effectively," said  Christopher Li, head of the Translational Research Program at the Fred Hutchinson Cancer Research Center in Seattle, and lead author of the study told Bloomberg.com via email.

Calcium channel blockers lower blood pressure by keeping calcium from entering cells of the blood vessels in the heart. This leads to the vessels relaxing, which further causes a drop in blood pressure. The use of these drugs has been linked with few cases of liver disease and certain mild, reversible cases of hepatic injury.

The present study included women between ages 55 and 74.  In the study group, 880 women had invasive ductal breast cancer while 1,027 had invasive lobular breast cancer and 856 had no cancer. Researchers then used the data to assess breast cancer risk and the participants' history of blood pressure and medication use.

They found that women who were taking calcium channel blockers for more than 10 years had over two times higher risk of developing breast cancer than women who weren't taking the drugs.

They also found no association between other high-blood pressure medications such as diuretics, β-blockers and angiotensin II antagonists and breast cancer.

"While some studies have suggested a positive association between calcium-channel blocker use and breast cancer risk, this is the first study to observe that long-term current use of calcium-channel blockers in particular are associated with breast cancer risk. Additional research is needed to confirm this finding and to evaluate potential underlying biological mechanisms," the study concluded.

The study is published in the journal JAMA Internal Medicine.