This study showed that 10 years of adjuvant tamoxifen reduced the risk of late recurrence in hormone receptor-positive breast cancer, which is a major problem. The study also showed that ‘patience is a virtue’,” stated formal discussant Ann Partridge, MD, Director of the Adult Survivorship Program at the Dana-Farber Cancer Institute in Boston.

The benefit of chemotherapy is seen primarily in years 1 to 5 after treatment, she said. However, the benefits of additional tamoxifen appear later. With 10 years of tamoxifen, the absolute reduction in tumor recurrence is 4%, and 10 years later, the absolute reduction in death is 2%.

Many postmenopausal women with early hormone receptor–positive breast cancer are now treated initially with an aromatase inhibitor, but the optimal duration of endocrine therapy with an aromatase inhibitor is not known. “Several studies are looking at this question, and we eagerly await results,” she noted.

Decision-making Factors

At present, the question is how to factor available data into decision-making regarding adjuvant hormonal therapy. This decision should be based on the individual patient and her personalized risk, Dr. Partridge continued. Factors such as stage, tumor biology, and gene expression profiles should be considered. Also, comorbidity and age will influence treatment decisions.

“The risks of extended tamoxifen are an important consideration for each individual. Serious adverse events include endometrial cancer, which occurred in about 3% of women on extended tamoxifen vs 1.6% on 5 years of tamoxifen. The symptoms can affect quality of life. Patient preferences and values should be taken into account. Minor side effects can become deeply troubling over time, and adherence is a challenge in the real world. Adherence to adjuvant tamoxifen wanes over time, and one can only wonder what will happen when we prescribe more extended endocrine therapy,” she said.

Current options for most postmenopausal women include an aromatase inhibitor for the first 5 years. Tamoxifen can be given after 5 years of aromatase inhibitor therapy, but data do not support continuing an aromatase inhibitor beyond 5 years, she said. Options for women who develop amenorrhea on tamoxifen include switching to an aromatase inhibitor after 5 years of tamoxifen. “Continued tamoxifen is reasonable if there is resumption of ovarian function,” Dr. Partridge noted.

No Prior Standard

“There is no prior standard for premenopausal women who remain premenopausal on tamoxifen. Extending tamoxifen is a great new option where there has been no prior standard. These women have the greatest potential for risk reduction from extended therapy and the lowest risk of toxicity. But there is a potentially greater effect on long-term quality of life and future fertility in this group of patients,” she stated. It is reasonable to stop therapy [for premenopausal women] if they want to preserve fertility, the absolute risks are high, or quality of life is a priority.

“These are difficult decisions for some women. They need support in making this decision. It may not be a one-time, 15-minute clinic visit,” Dr. Partridge concluded. ■

Disclosure: Dr. Partridge reported no potential conflicts of interest.