What is the recommended treatment for patients with hormone receptor positive breast cancer?

This paper reviewed and provided recommendations on treatment for breast cancer that is hormone receptor positive (presence of estrogen or progesterone receptor). 

Adjuvant endocrine therapy (treatment given after surgery) is highly effective for hormone receptor positive breast cancer. Tamoxifen (Nolvadex) taken for 5 years has long been the standard adjuvant endocrine treatment. Recently, it has been suggested that patients who are postmenopausal (no menstruation for a year) can also take an aromatase inhibitor (Femara, Arimidex).

A group of experts in the field looked at results from clinical trials and made recommendations.

Recommendations

Women who have not completed menopause should be offered tamoxifen for an initial 5 years. After 5 years, these women should receive tamoxifen for an additional 5 years. However, if they have completed  menopause during the inital 5 years of tamoxifen therapy, they should receive either tamoxifen for another 5 years or  an aromatase inhibitor for up to 5 years.

There are several options for women who are postmenopausal. The first option is tamoxifen for 10 years. A second option would be an aromatase inhibitor for 5 years as there is currently insufficient data to recomment use of an aromatase inhibitor for longer than this. A third option would be  tamoxifen first for 5 years then switching to an aromatase inhibitor for up to 5 years. The fourth option would be tamoxifen for 2 to 3 years and switching to an aromatase inhibitor for up to 5 years.

Overall, endocrine treatment after surgery increases overall survival and reduces risk of cancer returning. However, side effects like hot flashes (feeling of warmth around face) can occur. Risks associated with tamoxifen include blockage of blood vessels, uterine cancer, and endometrial cancer if tamoxifen is continued in the long term. Side effects of aromatase inhibitors include heart disease and osteoporosis (weak and brittle bones). 

The authors concluded that tamoxifen is now recommended for a duration of up to 10 years rather than 5 years in hormone receptor positive breast cancer. 

This study reviewed only evidence on durations of tamoxifen of greater than 5 years.