MHT doesn’t cause (or prevent) cancer or heart attacks

4 minute read

Years after women were frightened into avoiding hormone therapy, the study that started it all confirms they shouldn’t be.

The preliminary Women’s Health Initiative Study data that caused fears about hormone replacement therapy increasing breast cancer risk in 2003 is back with a follow-up, confirming that the treatment is fine.  

“The WHI findings should never be used as a reason to deny hormone therapy to women in early menopause with bothersome menopausal symptoms,” said author Dr JoAnn Manson, chief of Preventive Medicine at Brigham and Women’s Hospital and Professor of Women’s Health at Harvard Medical School.  

According to the Women’s Health Initiative Study update, published in JAMA this week, the hormone therapies available when the study began in 1993 did not increase risk of cancer, stroke or heart attack in women aged 50-60. It’s fine to use as indicated, for treating hot flushes, night sweats and other menopause symptoms. 

The evidence gathered from the cohort studied – women between the ages of 50 and 79 – did not support using it to prevent cancer, stroke, heart disease, dementia and a host of other conditions, they said.  

In addition, the evidence did not support using Vitamin D plus calcium for fracture prevention in women with typical risk whose diet was adequate. And a low-fat diet with more fruit, vegetables and grains did not prevent breast or colorectal cancer, but in the long term was associated with lower rates of death from breast cancer. 

The hormone trials were ended in 2002, three years earlier than planned, because the risk-to-benefit ratio appeared unfavourable. But the new data, from up to 20 years of follow-up, showed that it depended on age.  

“In both of the WHI hormone therapy trials, women younger than 60 years had a more favorable benefit-risk ratio than women aged 60 to 69 years or 70 to 79 years. This was primarily because of lower absolute risks of adverse events in younger women but also because of lower hazard ratios for several clinical event outcomes in younger women than in older women (especially in the CEE-alone clinical trial),” the authors wrote.  

The four WHI trials involved 68,000 post-menopausal women in the US aged 50-79 and were set up to investigate the effect of hormone therapy, calcium and vitamin D supplementation and low-fat diet on the prevention of heart disease, cancer (especially breast and colorectal cancer) and hip fractures.  

“In the early 1990s, nearly 15 million US women received [hormone therapy] prescriptions each year and HT was often (and increasingly) prescribed to try to prevent cardiovascular disease and other chronic diseases among women in both early and late menopause, whether or not the patient had hot flashes or other menopausal symptoms,” said Manson.  

“However, no randomised trials had been done in postmenopausal women to evaluate the benefits and risks of HT for chronic disease prevention. Ironically, the only randomised trial of oestrogen had been done in men!” 

The hormone therapy tested was conjugated equine oestrogens plus medroxyprogesterone acetate vs placebo in women with uterus in situ, and oestrogen alone vs placebo in women who’d had a hysterectomy. 

“Women … have more options for treatment now, including oestrogen in lower doses and delivered through the skin as a patch or gel, which may further reduce risks; non-hormonal treatments are also available,” said Dr Manson. 

Professor Deborah Bateson AM from the Daffodil Centre in Sydney said these findings confirmed what was already known: that hormone therapy is a useful option for treating menopause symptoms.  

“We want to make sure that that women are aware of that, and doctors feel confident in prescribing modern-day types of menopausal hormone therapy,” she told OR

“It’s taken a long time to overcome those fears. There’s been a concerted effort by people like the Australasian Menopause Society and Jean Hailes to get the information out. I think it’s just getting that confidence back and making sure that women have those choices.” 

JAMA 2024, online 1 May 

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