A recent trial has shown that extending tamoxifen treatment to 10 years in women with oestrogen receptor (ER)-positive disease reduces breast cancer recurrence and deaths from breast cancer.

The randomized controlled trial involved 6,847 women who either took tamoxifen for 10 years or took tamoxifen for 5 years followed by a placebo. Both groups of women were followed for up to 8 years after their treatment ended. The results showed that 15 years after the start of treatment, the risk of breast cancer recurrence was 25.1% in women taking tamoxifen for 5 years and 21.4% for women taking tamoxifen for 10 years. “This trial is great news for women with this type of breast cancer” stated Dr Caitlin Palframan, head of policy at Breakthrough Breast Cancer, UK ( BBC News , 5 Dec 2012).

However, taking tamoxifen for an additional 5 years is not risk free. Tamoxifen increases the risk of developing endometrial cancer, and this risk approximately doubled in women who took tamoxifen for 10 years, with 3.1% of these women developing this disease. In addition, many premenopausal women find the menopausal side effects of tamoxifen difficult. As Eric Winer, chief of women's cancers at the Dana-Farber Cancer Institute, USA, noted: “the benefit [identified in this study] isn't huge, it's modest”, meaning that younger women diagnosed with breast cancer will need to think carefully about their treatment options ( Boston Globe , 5 Dec 2012). The implications of these findings are also a matter of debate. Jennifer Litton, an oncologist at the MD Anderson Cancer Center, USA, felt that the findings were unlikely to herald a “sweeping change of practice” because of the superior benefit seen with aromatase inhibitors in postmenopausal women. But premenopausal women are not prescribed aromatase inhibitors and “for those women, we have no additional strategies” noted Winer ( Wall Street Journal , 5 Dec 2012).