Hormone Therapy and Breast Cancer Risk

Researchers have confirmed the association between hormone therapy use and increased breast cancer risk in a large observational study.

The study confirmed increased risks of breast cancer associated with long-term use of oestrogen-only therapy and combined oestrogen and progestogen therapy. The combined treatment associated with the lowest risk increase was estradiol-dydrogesterone, observed the researchers and published the findings in the British Medical Journal (BMJ).

Hormone replacement therapy (HRT) (also known as hormone therapy (HT) or menopausal hormonal therapy (MHT)) is prescribed to relieve the symptoms of menopause, which can be life-changing. A range of hormone combinations are available, each with different efficacy and side effects. HRT can bring several improvements to quality of life, and it can prevent osteoporosis. Concerns about adverse effects, particularly the increased risk of breast cancer associated with HRT. Current clinical guidelines recommend use of HRT for no longer than five years and have signalled that more information is needed about the risks of breast cancer associated with different types of HRT.

Yana Vinogradova et al aimed to assess the risks of breast cancer associated with different types and durations of hormone replacement therapy (HRT).

98611 women aged 50-79 with a primary diagnosis of breast cancer between 1998 and 2018, matched by age, general practice, and index date to 457498 female controls. Main outcome measures assessed were breast cancer diagnosis from general practice, mortality, hospital, or cancer registry records. Odds ratios for HRT types, adjusted for personal characteristics, smoking status, alcohol consumption, comorbidities, family history, and other prescribed drugs. Separate results from QResearch or CPRD were combined.

Key Findings

• Overall, 33703 (34%) women with a diagnosis of breast cancer and 134391 (31%) controls had used HRT prior to one year before the index date.
• Compared with never use, in recent users (<5 years) with long-term use (≥5 years), oestrogen-only therapy and combined oestrogen and progestogen therapy were both associated with increased risks of breast cancer (adjusted odds ratio 1.15 (95% confidence interval 1.09 to 1.21) and 1.79 (1.73 to 1.85), respectively).
• For combined progestogens, the increased risk was highest for norethisterone (1.88, 1.79 to 1.99) and lowest for dydrogesterone (1.24, 1.03 to 1.48).
• Past long-term use of oestrogen-only therapy and past short-term use of oestrogen-progestogen were not associated with increased risk. The risk associated with past long-term oestrogen-progestogen use, however, remained increased.
• In recent oestrogen-only users, between three (in younger women) and eight (in older women) extra cases per 10000 women years would be expected, and in oestrogen-progestogen users between nine and 36 extra cases per 10000 women years.
• For past oestrogen-progestogen users, the results would suggest between two and eight extra cases per 10000 women years.

For full article click on the link: 10.1136/bmj.m3873

Primary source: British Medical Journal