Fighting breast cancer using hormone-suppressing and bone-preserving drugs

In Switzerland, an average of 5,500 new cases of breast cancer in women are registered, and about 1,400 women die from breast cancer each year.

A large proportion of breast cancers are sensitive to hormones, the tumor cells having hormone receptors on their surface. One of the most frequent forms of breast cancer is sensitive to estrogens, which induce tumor growth. This type is called estrogen-responsive breast cancer. It can be treated with drugs which act on the metabolism of the estrogen in the body, which is mainly done after surgery, in order to prevent recurrence of the cancer. One of these drugs, tamoxifen, inhibits the estrogen receptors on the cell surface, whereas another one, the so-called ‘aromatase inhibitors’, directly suppress estrogen production.

On 24 July 2015, a meta-analysis was published in The Lancet, which integrated nine clinical trials and included data from 31,920 post-menopausal women affected by estrogen-receptor positive early breast cancer. It showed that aromatase inhibitors reduced cancer recurrence more efficiently than tamoxifen during the treatment by 30%. The 10-year breast cancer mortality rate was reduced by 15% by using treatment with aromatase inhibitors as compared to tamoxifen. When compared to women without endocrine treatment, mortality was even 40% lower.

A second study published the same day analyzed the effect of bisphosphonates on cancer recurrence and mortality in 18,766 women affected by early breast cancer. Bisphosphonates are commonly used to treat loss of bone mass in patients affected by osteoporosis. They can also be given to women with breast cancer treated with aromatase inhibitors in order to reduce the adverse effects of this treatment on the bones.

Tumor cells are known to be able to circulate in the body, and if they attach themselves to surfaces in the bone, they can stay quiescent for years. Sometimes they leave this state and start to form metastases. Thus, breast cancer can recur from bone or other tissues.

For premenopausal women, the study did not find any effects of bisphosphonate treatment on cancer recurrence or survival. However, for postmenopausal women, bisphosphonate treatment reduced the rate of breast cancer metastases in the bone and enhanced the breast cancer survival rate.

Both studies were published by the Early Breast Cancer Trialists’ Collaborative Group, an international group of researchers from many different institutions that was first created in 1985 and since coordinates research on breast cancer. The secretariat of the group is located at the University of Oxford Clinical Trial Service Unit in the UK.

Sources:
http://www.bfs.admin.ch/bfs/portal/de/index/themen/14/02/05/key/02/05.html
https://www.krebsinformationsdienst.de/tumorarten/brustkrebs/hormontherapie.php
http://dx.doi.org/10.1016/S0140-6736(15)61074-1
http://dx.doi.org/10.1016/S0140-6736(15)60908-4

Photo credit: Paul Falardeau via Flickr, CC 2.0