Putting these results in perspective, Peter Ravdin, MD, moderator of a San Antonio Breast Cancer Symposium press conference where ATLAS findings were discussed, said that in the United States, there is currently a different strategy for pre- and postmenopausal women. Tamoxifen is used as primary hormonal therapy in premenopausal women, because aromatase inhibitors are not effective, he continued.

“In postmenopausal women, aromatase inhibitors in general are slightly superior to tamoxifen and represent the standard of care,” he said. Dr. Ravdin is Director of the Breast Health Clinic at the Cancer Therapy and Research Center at the University of Texas Health Sciences Center San Antonio, Texas.

“The results of ATLAS are most relevant for younger women. When they approach 5 years of therapy, usually we tell them to stop. ATLAS tells us that 10 years are superior to 5 years. I’m going to be comfortable telling them that. The risk of endometrial cancer is very low in premenopausal women. In my opinion, the results of this trial will impact treatment of premenopausal women,” Dr. Ravdin stated.

Risk vs Benefit

The question is open about how long to continue hormonal therapy, whether with tamoxifen or aromatase inhibitors. “The biology of the disease is such that some women are fated to have late relapses, and ATLAS suggests we can do better by treating women with hormonal therapy beyond 5 years,” he said.

Dr. Ravdin cautioned that it is important to weigh risk vs benefit. “Women at high risk of late relapse, with positive nodes, and/or bigger tumors are strong candidates for continuing therapy. But a patient with a small grade 1 tumor and low risk of early and late relapse may decide she doesn’t want 5 more years of tamoxifen or hormonal therapy. The side effects can be very bothersome, and some women will have difficulty considering therapy beyond 5 years for a small benefit—an additional one-third reduction of a very small risk to begin with,” he stated.

Important Implications

These results are relevant for premenopausal women for whom aromatase inhibitors are not an option, and also relevant to a wider range of women who may not want to take aromatase inhibitors because they find the side effects difficult, said Sandra M. Swain, MD, FACP, 2012–2013 President of ASCO and Medical Director of the Washington Cancer Institute, MedStar Washington Hospital Center, Washington, DC.

“These results have important implications in the United States, for patients who cannot tolerate aromatase inhibitors, which is many women. This is an underappreciated problem. Women are concerned about quality of life, and you can’t expect women in their 50s and 60s who are already beginning to feel the effects of aging to suffer for a 2% absolute benefit,” she stated.

ATLAS also has important global health implications, Dr. Swain continued. “In some countries, money is a big issue, and tamoxifen is an inexpensive drug. Longer treatment saves lives,” she said. ■

Disclosure: Drs. Ravdin and Swain reported no potential conflicts of interest.