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Heart Drugs Affect Breast Cancer Risk: Good and Bad
The first observational study of long-term antihypertensive use and breast cancer risk has found that calcium-channel blockers are associated with a more than 2-fold increased risk and that angiotensin-converting-enzyme (ACE) inhibitors are associated with a reduced risk.
These findings come from a study published online August 5 in JAMA Internal Medicine.
Women who had taken calcium-channel blockers for 10 years or more had more than double the usual risk for invasive ductal breast carcinoma (IDC) (odds ratio [OR], 2.4) and for invasive lobular breast carcinoma (ILC) (OR, 2.6). The researchers also observed a possible association between the long-term use of ACE inhibitors and reduced risks for both IDC (OR, 0.7) and ILC (OR, 0.6), although the risk estimate for IDC was within the limits of chance.
No Changes in Clinical Practice Recommended Yet
This first study relates to long-term antihypertensive use. It was an observational study, not a clinical trial. We can suggest an association, but we cannot infer any causal relation at this point,” lead author Christopher Li, MD, PhD, from the Fred Hutchinson Cancer Research Center in Seattle, told Medscape Medical News.
The antihypertensives included ACE inhibitors, angiotensin-receptor blockers, beta blockers, calcium-channel blockers, diuretics, and combination antihypertensive preparations, regardless of indication.
Calcium-channel blockers are among the most frequently prescribed medications in the United States; they accounted for nearly 98 million of the more than 678 million prescriptions filled in 2010.
Subjects who had used antihypertensives for 6 months or longer and were still using them were classified as current users, subjects who had used them for 6 months but were no longer using them were classified as former users, and subjects who had used them for less than 6 months were classified as short-term users.
In the regression analyses, potential confounders included age, county of residence, other commonly used medications, comorbid conditions (cardiovascular disease, diabetes, hyperlipidemia, depression), alcohol use, and estrogen-receptor status.
Increased Risk After 10 Years
Dr. Li told Medscape Medical News that they were surprised by the magnitude of the risk associated with calcium-channel blockers and by the decrease associated with ACE inhibitors.
The mechanism behind the apparent calcium-channel blocker effect is not known, Dr. Li explained, but some researchers suspect that these drugs might increase cancer risk by inhibiting apoptosis.
If the 2- to 3-fold increase in risk found in this study is confirmed, long-term calcium-channel blocker use would take its place as one of the major modifiable risk factors for breast cancer. Thus it is important that efforts be made to replicate the findings.
JAMA Intern Med. Published online August 5, 2013. Abstract, Commentary
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