Women who take a common type of medication to control their blood pressure are not at increased risk of developing breast cancer due to the drug, according to new study by researchers at the Intermountain Medical Center Heart Institute in Murray, Utah.

Researchers analysed the records of more than 3,700 women who had no history of breast cancer, and who had long-term use of calcium channel blocker medications to control their blood pressure.

Researchers found only a minimal increase in risk in one study and a 50 percent reduced risk in a second, leading them to recommend the continued use of these important medications to help prevent heart attack and stroke.

Findings from the Intermountain Medical Center Heart Institute study were presented at the 2014 American Heart Association Scientific in Chicago on the 19th of November.

Calcium channel blockers are commonly used to help prevent calcium from entering cells of the heart and blood vessel walls, resulting in lower blood pressure.

"We found no robust data that calcium channel blocker medications increase a person's risk of breast cancer," said Jeffery L. Anderson, MD, a cardiologist and researcher at the Intermountain Medical Center Heart Institute.

"Given the important role calcium channel blocker medications play in treating heart conditions, we think it's premature to discontinue their use. At this point we recommend that patients continue taking these medications to treat their hypertension."

The Intermountain Heart Institute study was in response to a similar study released last year by the Fred Hutchinson Cancer Research Center in Seattle.

That study suggested that the odds of getting breast cancer was 2.5 times higher for women who take calcium channel blocker medications.

Results of the Intermountain study indicated small to no increased risk.

The Intermountain Medical Center Heart Institute study carefully examined data collected from more than 3,700 women ages 50 to 70 with no history of breast cancer in two Intermountain Healthcare databases.

For each group, researchers compared women who were prescribed calcium channel blocker medications to similar women who weren't prescribed the medications.

In their review of a general population medical records database, researchers found the odds of breast cancer to be 1.6 times higher by using calcium channel blockers, which was significant, but much smaller than reported by the Seattle group.

But, in contrast, in the data collected from patients treated in the Intermountain Cardiac Catheterization Laboratory, a reverse relationship was found – a 50 percent reduction in risk of developing breast cancer for women who took the calcium channel blockers.

The contrasting results found in these two independent analyses led researchers at the Intermountain Medical Center Heart Institute to conclude that it is likely not the medication that caused the changes in breast cancer risk but other factors (e.g., selection biases).

The study was led by Jeffrey Anderson, MD, and Uyen Lam, MD, from the Intermountain Medical Center Heart Institute and the Internal Medicine Residency Program at the University of Utah School of Medicine.

The Intermountain Medical Center Heart Institute study and the Fred Hutchinson study were both analyses of existing patient data and not clinical trials.

Both studies recommend further research. 

Source: Intermountain Medical Center