Hormone-modulating breast cancer treatments (HMTs) like tamoxifen and aromatase inhibitors (AIs) could reduce a patient’s risk of developing dementia or Alzheimer’s later in life.
Tamoxifen is a selective estrogen receptor modulator (SERM) that’s often prescribed after surgery or other breast cancer treatment to prevent the cancer from coming back. It is only prescribed for hormone-receptor-positive breast cancer, or to reduce breast cancer risk in women who have a high risk of developing the disease but haven’t yet gotten it.
Like tamoxifen, AIs are also only effective against hormone-receptor-positive breast cancers. They block an enzyme called aromatase, which is responsible for turning the hormone androgen into estrogen. By stopping this enzyme and reducing estrogen production, any hormone-fueled cancer cells will find it difficult to grow. AIs can’t stop the ovaries from producing estrogen, so this treatment is primarily used in postmenopausal women.
Both types of treatment seem to reduce the risk of developing neurodegenerative disease (NDD).
“The fact that breast cancer is the second most common cancer in women (after skin cancer) and that women are disproportionately affected by AD [Alzheimer’s disease] and related dementia provides us with an opportunity to reduce the global disease burden of NDDs,” wrote the study’s authors.
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The study was published in JAMA Network Open. Researchers looked at data from a Humana insurance claims database that primarily contained patients who lived in the southeastern United States. They looked at the data of 57,843 breast cancer patients who were at least 45 years old over a period of ten years, from January 1, 2007, to March 31, 2017.
Of the 57,843 total patients, 18,126 patients (31.3%) had undergone HMT, including tamoxifen, raloxifene, nonsteroidal AIs (anastrozole or letrozole), or a steroidal AI (exemestane), and 39,717 patients did not undergo HMT. The HMT group had an average age of 76.2 and the non-HMT group had an average age of 76.8 years.
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Patients who received HMT were significantly less likely to be diagnosed with a neurodegenerative disease like dementia. They had a 12.5% chance, while the non-HMT group had a 14.3% chance.
Researchers found that the percentage of those with Alzheimers disease was 4.9% in the HMT group, compared to 6.0% in the non-HMT group. The HMT group also had a lower risk of dementia, with 10.4% being diagnosed with dementia versus 11.8% in the non-HMT group. The mean follow-up time was five and a half years.
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While HMTs like tamoxifen and AIs caused the greatest reductions in NDDs, a SERM called raloxifene did not offer any protection.
“The protection associated with the SERMs was exclusively due to tamoxifen and not to raloxifene,” the study’s authors wrote. “This finding might explain why previous studies using SERMs were not found to be effective because raloxifene was the focus of several of these AD trials.”
As for aromatase inhibitors, all types offered a reduction in the risk for Alzheimer’s and dementia, but exemestane (a steroidal AI) had the strongest reduction when compared to anastrozole or letrozole (which are nonsteroidal).
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“With the increased life expectancy seen after treatment, therapy selection for breast cancer should include a careful discussion of the risks and benefits of each treatment option that may be associated with a reduced risk of neurodegenerative disease,” the authors wrote.