The impact of breast cancer treatments on bone health.

By Dr Justus Apffelstaedt, specialist surgeon with an interest in breast, thyroid and parathyroid health as well as soft tissue surgical oncology

Breast cancer is the most diagnosed cancer in women[1]. A comprehensive research effort stretching back more than half a century makes breast cancer the most well understood cancer, with advanced screening and treatment therapies available. Women are surviving longer, have increased remission rates and, in many cases, live as long as their cancer-free counterparts.

Consequently, ‘life after breast cancer’ is an increasingly important topic due to the negative effects of life-saving breast cancer treatments such as cardiovascular toxicity, bone loss and more.

Treatment induced bone loss is one of the most well-researched side effects of common breast cancer treatments. After the age of 30, all women and men experience some degree of bone loss – a natural consequence of aging. In women, however, the oestrogen deprivation of menopause is a contributing factor. Yet, it is only some women that will lose enough bone to merit anti-bone loss treatment.

According to a 2020 research paper^[2], around 200-million individuals get osteoporosis in their lifetime. Osteoporosis is a severe form of bone loss) and estimates are that around 1 in 3 women will experience a fragility fracture of hip, spine or wrist.

For women undergoing breast cancer treatment, it is a fact that some of their treatments will result in treatment-induced bone loss. For those who are already at risk of bone density loss, this can result in fragility fractures if not managed from the start of treatments. Fragility fractures decrease the quality of life and, if a weight bearing bone such as the femur is involved, can lead to loss of mobility and through complications, even premature death.

Women who are at risk of accelerated bone loss include:

• Smokers;
• Excessive alcohol drinkers;
• Those with low body mass;
• Those with a personal or parental history of non-traumatic fractures and rheumatoid arthritis; and
• Those with a family history of osteoporosis.

The conventional prevention of bone loss includes stopping smoking, consuming very moderate amounts of alcohol, and increasing physical activity. Calcium and Vitamin D supplements are also recommended, along with bone density screening from the onset of menopause.

In the case of women undergoing breast cancer treatments, prevention of excessive bone loss needs to be a priority.

Post-menopausal women and treatment induced bone loss

It’s known that the treatments linked to bone loss are aromatase inhibitors (AIs). AIs lower oestrogen levels by stopping the aromatase enzyme in fat tissue from changing other hormones into oestrogen. Chemotherapy also has a bone loss effect.

Whilst healthy post-menopausal bone loss is about 1-2% change per year, with AIs, post-menopausal women lose bone at around 2-3% per year.

According to the patient’s bone-density risk factors, the medical team can prescribe various treatments to prevent bone loss and to limit fragility fractures.

Pre-menopausal women and treatment induced bone loss

Treatment with AIs in pre-menopausal women is always accompanied by ovarian function suppressors. These cause an artificial menopause. Chemotherapy-induced ovarian failure (CIOV) also has to be considered. Data on the effects of Tamoxifen are scanty. This common medication is usually given in conjunction with ovarian function suppressors or after chemotherapy; making an assessment of the particular effects of the individual agents on bone health very difficult.

The good news, however, is that despite treatment-induced bone loss, few pre-menopausal women require treatment for severe bone loss (osteoporosis), as they are nearer to their peak bone mass.

Lifestyle changes, supplements and regular bone density screening suffice for the vast majority of young women.

A bone-loss risk assessment must be undertaken by the medical team before women commencing breast cancer treatment. Regular bone density tests, counselling on lifestyle changes and monitoring must be part and parcel of the treatment plan but this is unfortunately, often overlooked.

Whilst bone loss may be somewhat scary, it must be weighed up against the chance of a breast cancer remission or cure. Together with a medical team who knows what it’s doing, this risk can be managed.