A Study Of 728K Women Found Up To 46% Lower Risk Of This Cancer
Menopause hormone therapy (MHT) is often used to ease symptoms like hot flashes and night sweats, but could it also be connected to women's long-term cancer risk?
Researchers are exploring whether replacing hormones that decline during menopause might influence the chances of developing colorectal cancer.
A large Finnish study involving more than 728,000 women investigated this connection, looking at whether women who used hormone therapy had different cancer rates than those who didn't, and whether the type of treatment or length of use made a difference.
About the study
Researchers used Finland's national health records to track hormone therapy prescriptions and cancer diagnoses.
They identified 364,304 women over age 40 who had purchased systemic MHT at least twice within a year between 1994 and 2019. Each woman was matched with a woman of the same age who hadn't used the treatment.
Both groups were followed for an average of 18 years.
Researchers tracked colorectal cancer diagnoses and compared outcomes based on the type of hormone therapy and how long women used it.
Some hormone therapies were linked to lower cancer risk
Colorectal cancer was slightly less common among women who used MHT than those who didn't.
Although the difference in diagnoses was small (1.3% versus 1.4%), the researchers found a more meaningful difference when they looked at the women's risk over time.
MHT use was associated with a 10 to 18% lower risk, particularly among women who had used it for at least five years.
The association also differed depending on the treatment:
- Estrogen-only therapy: Linked to a 19% lower colorectal cancer risk.
- Combined estrogen-progestogen therapy: Linked to an 8% lower risk.
- Tibolone: A synthetic hormone therapy that has estrogen-like, progesterone-like, and testosterone-like effects in the body. It was associated with the largest reduction in colorectal cancer risk, at 46%, although fewer women in the study used it.
Among combined therapies, treatments containing dydrogesterone were associated with a greater reduction in risk than those containing norethisterone or medroxyprogesterone acetate.
The association also continued for more than five years after women stopped using MHT.
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Why MHT isn't a cancer prevention strategy
Before getting too excited about the numbers, there's an important detail to understand.
This was an observational study, meaning researchers tracked women's existing hormone use and health rather than assigning some to take MHT and others not to.
That means they found a connection, but can't say hormone therapy itself was responsible for the lower cancer risk.
There were also some gaps in the data. Researchers didn't have information on several factors that can influence colorectal cancer risk, including body weight, smoking, inflammatory bowel disease, and a history of colon polyps.
Women taking MHT may also visit their doctors more regularly, giving them more opportunities to have cancer detected.
This could actually make the difference between the groups appear smaller.
What to consider if you're using or considering MHT
If menopause hormone therapy is on your radar, here's how to put these findings into perspective:
- Talk through your options: Ask your health care provider about the potential benefits and risks of MHT based on your age, menopause symptoms, medical history, and the type of treatment you're considering.
- Don't change your treatment based on this study: The findings don't establish MHT as a way to prevent colorectal cancer, so don't start, stop, or switch formulations because of the reported risk reductions.
- Stay current on colorectal cancer screening: Whether you use MHT or not, follow recommended screening guidelines. A possible protective association isn't a substitute for early detection.
The takeaway
Some menopause hormone therapies were associated with considerably lower colorectal cancer risk, but that doesn't mean taking hormones will prevent cancer.
Think of this as another interesting clue about how hormones influence women's health, not a new reason to reach for a prescription. That being said, hormonal changes with age are a valid reason to talk to your doctor about your treatment options.
