There is no conclusive evidence that HRT significantly increases the risk of breast cancer. There just isn’t! But there’s the perception that there’s conclusive evidence, and therein lies the problem.
In Estrogen Matters, authors Avrum Bluming, MD, and Carol Tavris, PhD, explain in great detail why there’s a widespread belief—even by doctors—that HRT increases the risk.
While I don’t want to get deep into the science, I will highlight a few things that could help you quickly grasp where things went wrong. First, there’s that 2002 Women’s Health Initiative (WHI) study—the one we’ve mentioned in posts about estrogen and cognition, heart health, and bone health. That study found that women randomly assigned to take estrogen and progestin had a 26 percent increase in risk. That sounds big but, in the words of the report itself, that means it “almost reached a nominal statistical significance.” It may have been almost statistically significant, but the fact remained that it was not statistically significant.
The media latched onto the “26 percent increase” (it made for a compelling headline) but didn’t mention that 26 percent was not statistically significant. If a result isn’t statistically significant, that means it could have arisen randomly. Still, the WHI halted the study, everyone panicked, and the prescription rate for HRT fell by 50 percent.
To put the risk of HRT in perspective, the authors bring up other “risk factors” associated with the development of breast cancer. “The relative risks in almost all cases are very low, and the use of HRT is virtually the lowest, being less risky than eating fish or grapefruit, using antibiotics, or being a flight attendant.”
The second thing I want to highlight is that the WHI updated its study in 2006 and it found no increased risk of breast cancer. None. The entire reason that the study had been halted had vanished. “This news,” the authors wryly note, “did not make headlines.” No wonder so many women and their doctors and even professional associations still believe there’s incontrovertible proof that HRT increases the risk of breast cancer.
One final note: Even if you’ve had breast cancer, don’t automatically rule out HRT. There have been meta-analyses (comparing data from multiple studies) that show women who began HRT three to five years after their diagnoses and remained on it for an average of three years had a 10 percent decrease in chance of recurrence. Talk to your doctor!