Aug. 06--Long-term use of a common class of high-blood-pressure drugs called
calcium-channel blockers may be associated with higher risk of breast cancer in
older women, a new study by the Fred Hutchinson Cancer Research Center has
Researchers interviewed 2,763 women in the Puget Sound area -- two-thirds of
whom had breast cancer -- about the drugs they took for high blood pressure, or
hypertension. Only calcium-channel blockers were found to be associated with
The proportion of women who got breast cancer was double in the group that had
been taking those drugs for 10 or more years. Common calcium-channel blockers
include amlodipine (Norvasc) and diltiazem (Cardizem).
The results were published online Monday by JAMA Internal Medicine.
Despite the correlation, researchers said the study cannot prove a causal link
between the drugs and breast cancer because it was not a randomized trial, and
because past studies have found conflicting results. More research is needed to
establish any definitive link.
"These are some intriguing findings, but we do not think they should change
current clinical practice in any way," said Christopher Li, the study's lead
researcher and an epidemiologist at the Hutch.
Doctors warn that the benefit of taking medication for high blood pressure
outweighs the possible risks raised in the study. High blood pressure can damage
the blood vessels, heart and kidneys, which can lead to stroke, coronary heart
disease and kidney problems.
In the current study, interviewers from the Hutch visited women 55 to 74 years
old in King, Snohomish and Pierce counties between 2000 and 2008. They asked the
women about their medical history, and in many cases transcribed prescription
information straight from pill bottles, cutting down on recall errors.
That the study included only Puget Sound-area women may limit its wider
applicability, experts say.
"The demographics here don't reflect the multicultural America," said Keith
Ferdinand, a cardiologist and board member of the American Society of
Hypertension, who was not involved in the study. He called the results
"provocative," but said plenty of associations in observational studies such as
this one don't pan out in randomized trials.
On the whole, a larger proportion of women in the study were white and wealthy
compared to the general population.
Race can be a factor in choosing blood-pressure medication: Another class of
drugs called beta blockers tend to be less effective when prescribed alone in
African-Americans, who are especially prone to high blood pressure. There are
several different types of hypertension drugs that work through independent
biological mechanisms, and patients are given a combination tailored to their
Calcium-channel blockers are the fourth most commonly prescribed class of
hypertension drugs. Generic versions are available, and nearly 98 million
prescriptions for these drugs were filled in 2010. Calcium-channel blockers also
generally have mild side effects.
The drugs lower blood pressure by relaxing muscles in the blood vessels and
heart. However, calcium widely affects all cells in the body, and the study's
author Li suggested calcium-channel blockers may increase cancer risk because
they prevent programmed cell death of abnormal cells. This has not yet been
proven by research.
Meanwhile, high blood pressure does cause cardiovascular disease, which is the
leading cause of disease for women, over cancer.
"Managing hypertension is very important because of the negative health
effects," Li said. "That is much more important at this point than this very
Sarah Zhang: 206-464-2195 or firstname.lastname@example.org. On twitter @sarahzhang
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