Women who take calcium channel blockers for more than 10 years to treat hypertension are at greater risk of developing breast cancer, according to a study published today in JAMA Internal Medicine.
Most individuals who begin hypertension treatment must take it for the rest of their lives. To better understand how such long-term exposure may affect women’s health, a team of researchers from the Fred Hutchinson Cancer Research Center in Seattle conducted a population-based case-control study of women in the Seattle area aged 55 to 74 years.
The study included 880 women with invasive ductal breast cancer, 1027 with invasive lobular breast cancer, and 856 controls without cancer. Women who used calcium channel blockers for 10 years or more had a higher risk of ductal breast cancer (odds ratio [OR], 2.4; 95% CI, 1.2-4.9) and a higher risk of lobular breast cancer (OR, 2.6; 95% CI, 1.3-5.3). Taking calcium channel blockers for shorter time periods or taking another class of antihypertensive drug was not associated with having a higher breast cancer risk.
Christopher I. Li, MD, PhD, lead author and head of the Translational Research Program at Fred Hutchinson, discussed the findings with news@JAMA.
news@JAMA: What led you to look for a relationship between antihypertensives and breast cancer?
Dr Li: This is a question we’ve been interested in for some time. Several years ago, a colleague published a small study that found a relationship with calcium channel blockers. So we designed a longer-term study. Calcium channel blockers have only become more widely used over the past few decades, so this is the first time we’ve been able to look at long-term use.
news@JAMA: What do you make of the conflicting results from your study and others?
Dr Li: This is really the only one looking at long-term use. Similar to the other groups’ studies, we found no risk with short-term use. Women may need to take them for a long time to have this effect.
news@JAMA: Did you find any reason for concern with other classes of antihypertensives?
Dr Li: No, we didn’t see an increased risk with any other antihypertensives.
news@JAMA: Is there a plausible mechanism to explain this association?
Dr Li: At this point, it’s speculative. There is no confirmed biological mechanism. One potential explanation is that the body regulates apoptosis [cell death] by opening and closing calcium channels. During the process, calcium channels open up, and an influx of calcium causes the cell to become dysregulated, burst, and die. That is how the body weeds out bad cells. There is a hypothesis that taking calcium channel blockers creates an environment that allows cancer cells to thrive, but that is very speculative.
news@JAMA: What additional research is needed?
Dr Li: We need to see if this result is replicated in other populations, starting by looking at data from other studies or administrative data.
news@JAMA: What should physicians or women know about your findings?
Dr Li: I think the main thing is these are intriguing results. It’s a somewhat unexpected finding. I don’t think it should change current management of hypertension. Women shouldn’t read too much into it or change anything they are doing right now.