Epidemiology of breast cancer
Breast cancer is a common malignancy. Although more and more women are surviving the disease, each year in the UK there are over 55,000 new breast cancer cases: which equates to over 1,000 diagnosed each week. In the US, there are some 250,000 new breast cancer cases diagnosed each year: nearly 5,000 a week. Between 1993 and 2016 the incidence of breast cancer in the UK increased by 24%. Over a similar period, breast cancer incidence in the US declined, but an increasing trend of some 1.1% was observed among American Asians. In China, between 2000 to 2013, breast cancer increased at an annual rate of around 3.5%. Breast cancer rates in China are higher in urban areas than in rural areas: the higher the population density, the higher the rate. It is not altogether clear why breast cancer incidence is increasing. Experts suggest that breast cancer is a complicated disease with a variety of causes. Most cases of the disease are not linked to a family history. Around 5% of people diagnosed with breast cancer have inherited a faulty BRCA1 or BRCA2 gene. However, if you have a faulty gene, it does not mean that you will automatically develop breast cancer, but you are at higher risk. Out of every 100 women with a faulty gene, between 40 and 85 will develop breast cancer in their lifetime. Optimal therapy for breast cancer often requires several different treatment modalities including surgery, radiation, chemotherapy and hormone therapy (see below).
Cost of breast cancer treatment in the UK The cost of treating breast cancer in the UK is significant and rising. Findings of research on the treatment costs of breast cancer published in the August 1999 edition of The Breast estimated that the average cost per case of breast cancer in the UK to be £7,247 (US$9,418). Although the estimate is dated, it provides a guide. With 55,000 new cases of breast cancer diagnosed each year, the annual cost of treating the newly diagnosed alone, would be about £0.4bn (US$0.52bn). According to the UK charity Breast Cancer Now, an estimated 840,000 women living in the UK have been diagnosed with breast cancer and the charity predicts that this figure will increase to 1.2m over the next decade. Thus, ceteris paribus, we can assume that the current annual cost of treating breast cancer in the UK is significantly higher than £0.4bn and this figure is expected to increase substantially by 2030.
Hormones and hormone therapy
Hormones are chemical messengers secreted directly into your bloodstream, which carry them to organs and tissues of your body to exercise their functions. Oestrogen and progesterone are steroid hormones produced by the ovaries in premenopausal women and by some other tissues, including fat and skin, in both premenopausal and postmenopausal women. These hormones play a critical role in regulating reproduction. Oestrogen promotes the development and maintenance of female sex characteristics and the growth of long bones. Progesterone plays a role in the menstrual cycle and pregnancy.
Similar hormones are produced artificially either for use in oral contraceptives or to treat menopausal and menstrual disorders. Oestrogen and progesterone also promote the growth of some breast cancers, which are called hormone-sensitive (or hormone-dependent) breast cancers. Hormone-sensitive breast cancer cells contain proteins called hormone receptors, which become activated when hormones bind to them. The activated receptors cause changes in the expression of specific genes that can stimulate cell growth.
Anastrozole is a hormone therapy (also called hormonal therapy and endocrine therapy), which slows or stops the growth of hormone-sensitive tumours by either blocking the body’s ability to produce hormones or by interfering with the effects of hormones on breast cancer cells. Anastrozole blocks a process called aromatisation, which changes sex hormones called androgens into oestrogen. This happens mainly in the fatty tissues, muscle and the skin and needs a particular enzyme called aromatase.
Anastrozole belongs to a group of drugs called aromatase inhibitors, which are specifically designed to treat postmenopausal women diagnosed with hormone-receptor-positive, early-stage breast cancer. It is most often prescribed as an adjuvant therapy (after surgery) to decrease the risk of your cancer returning but can also be used in the neoadjuvant setting (prior to surgery) to decrease the size of your cancer in the breast. Hormone blocking therapy is also used to treat breast cancer that has recurred or spread. Most hormone blocking therapy drugs such as anastrozole are taken daily in pill form.
Anastrozole also may be given to reduce the risk of breast cancer in women who have not had breast cancer but have an increased risk of developing it because of their family history. Most experts suggest that your breast cancer risk should be higher than average for you to consider taking anastrozole as a preventative strategy. If your cancer is hormone receptor negative, then anastrozole will not be of any benefit, because these cancers do not need oestrogen to grow and usually such cancer cells do not stop growing when treated with hormones that block oestrogen from binding.
Reasons for the relatively low uptake of anastrozole
There are at least three probably reasons for the relatively low uptake of anastrozole. These include: (i) doctors becoming so used to prescribing the gold standard tamoxifen as an adjuvant hormone therapy, (ii) doctors wanting to be convinced about anastrozole’s long term benefits, and (iii) doctors wanting assurance about anastrozole’s minimal side effects.
Tamoxifen is the oldest and most-prescribed aromatase inhibitor and for the past three decades has become the standard of care as the adjuvant treatment of postmenopausal women with hormone-responsive early breast cancer. The drug reduces the risk of breast cancer returning by 40% to 50% in postmenopausal women and by 30% to 50% in premenopausal women. Notwithstanding, over the past two decades a new generation of aromatase inhibitors have been developed, and anastrozole is one of these. How does anastrozole compare with the gold standard tamoxifen?
Tamoxifen and anastrozole compared
Findings of two long-term comparative clinical studies undertaken in North America and Europe involving over 1,000 women with oestrogen receptor positive advanced breast cancer, showed that anastrozole is better than tamoxifen for: (i) increasing the time before the cancer returns in those who experience recurrence, (ii) reducing the risk of the cancer spreading to other parts of the body and (iii) reducing the risk of a new cancer developing in the other breast.
Significantly, studies have shown that anastrozole avoids two of tamoxifen's more serious side-effects: an increased risk of developing a blood-clotting disease and an increased risk of developing womb cancer. Anastrozole can make bones weaker and so it is not recommended for women with osteoporosis and also it can cause stiff joints, hot flushes and vaginal dryness, which clinicians need to recognize and manage. But overall, the benefits of anastrozole over tamoxifen were maintained without a detrimental impact on quality of life. However, anastrozole is not a therapy for premenopausal women because it blocks the hormone oestrogen and in effect creates a drug-induced menopause.
Increasing the uptake of anastrozole
For healthcare systems to function effectively and efficiently we expect doctors and patients to behave rationally and make effective and efficient decisions. Traditionally, the rational choice model, which is predicated upon the belief that all human beings (including doctors and patients) act rationally in their own self-interest, has been used to influence people to behave in desirable ways. However, evidence suggests that, despite the well-founded theory and sound evidence to support it, the rational choice approach does not appear to work that well in practice.