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Hormone Replacement Therapy and the Risk of Breast Cancer

Nov 02 , 2022 | 2 min read

Frequently women in their late 40s and 50s begin experiencing symptoms such as hot flashes, mood swings, disturbed sleep, and vaginal dryness, among others. Periods tend to become irregular and shorter. These symptoms arise from a natural decline in reproductive hormones, such as oestrogen and progesterone, as women transition to menopause.

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These menopausal symptoms can be of varying degrees and severity. Some experience mild discomfort and can tolerate it, whilst others have significant physical and emotional distress which needs intervention. One such intervention is Hormone Replacement Therapy or HRT, which is often prescribed to control menopausal symptoms. It constitutes the cyclic administration of oestrogen with or without progesterone. There has always been a raging debate about the adverse effects of HRT, which is the increased risk of breast cancer.

Factors like obesity and lack of exercise are are associated with the increased risk of breast cancer post-menopause. Obesity increases the risk of breast cancer even without HRT use, which is significant enough to negate any additional risk of HRT. Obesity also increases the risk of recurrences in post-menopausal breast cancer survivors. Moderate exercise has a significant positive impact. 20 minutes daily can reduce the risk of breast cancer by almost 20-30%. Smoking and alcohol consumption are other important risk factors, and no amount of alcohol consumption is considered safe.

Hormone Replacement Therapy is also associated with a small but significant risk of cancer. The risk varies depending on the type of HRT and is incremental with oestrogen-only replacement, followed by oestrogen with intermittent progesterone and highest for oestrogen plus daily progesterone replacement. A large study published in Lancet shed light on the percentage of increased risk. Authors deduced that an average-weight woman in her 50s has an absolute 6.3% risk of developing breast cancer over the next 20 years.

With the 5-year use of HRT, this risk increases by an additional 2% (8.3%) with oestrogen plus daily progesterone, 1.4% (7.7%) with oestrogen plus intermittent progesterone and 0.5% (6.8%) with oestrogen only during the use and over the next 15 years. This means an additional 1 in 50 women will develop breast cancer with oestrogen plus daily progesterone and 1 in 70 women with oestrogen plus intermittent progesterone during this period of 20 years. This risk is almost doubled when the use of HRT is increased from 5 years to 10 years. Women who start HRT earlier, between 30-39 years or 40-49 years, also have additional risk.

Women who experience these symptoms require a detailed discussion with their primary gynaecologists to understand the need for HRT and its associated risks. Also, there are multiple other remedies available that they can understand and be counselled about, including non-hormonal medicines for symptom control and regular physical exercises. If they are experiencing severe distressing symptoms, short-term HRT can be prescribed, as it has been seen that HRT for less than a year is not associated with an increased risk of cancer. It is always better to make informed decisions.