cancer cells attackingAn extended course of hormone therapy after treatment could prevent the recurrence of breast cancer in postmenopausal women with early breast cancer, new data presented at the American Society of Clinical Oncology (ASCO) Annual Meeting has revealed.

The findings follow a randomised Phase 3 clinical trial, MA.17R, which found that postmenopausal women with early breast cancer benefit from extending aromatase inhibitor (AI) therapy with letrozole (Femara) from 5-10 years. Following 5 years of an AI and any duration of prior tamoxifen, women who received letrozole for 5 additional years had a 34% lower risk of recurrence than those who received placebo.

The trial was led by the Canadian Cancer Trials Group with participation from the National Clinical Trials Network. These results were discussed in ASCO’s Plenary Session, which featured 4 abstracts deemed to have the greatest potential to impact patient care, out of the more than 5,000 abstracts featured at the ASCO Annual Meeting.

Paul Goss, MD, FRCP, PhD, director of Breast Cancer Research at Massachusetts General Hospital in Boston, Massachusetts and Professor of Medicine at Harvard Medical School, and lead author, said: “Women with early-stage hormone-receptor positive breast cancer face an indefinite risk of relapse.

“The study provides direction for many patients and their doctors, confirming that prolonging aromatase inhibitor therapy can further reduce the risk of breast cancer recurrences. Longer AI therapy also showed a substantial breast cancer preventative effect in the opposite, healthy breast.”

Speaking for ASCO, breast cancer expert Harold J. Burstein, MD, FASCO, said: “These data are important to the millions of women around the world with ER positive breast cancer, and suggest that longer durations of widely-available therapy reduce the risk of cancer recurrence, and prevent second cancers from arising,” said Harold J. Burstein, MD, FASCO, ASCO expert in breast cancer.

“Ten years of any therapy is a long time. Fortunately, most women tolerate extended treatment reasonably well, with few side effects. Now, women can talk with their clinical team and make informed decisions to extend adjuvant endocrine therapy, or not.”

Patient overall quality of life was comparable between the 2 groups. However, small differences in physical role functioning in favour of placebo was observed, but these were not considered clinically significant.

Julie Lemieux, MD, lead author of the analysis of patient-reported outcomes from MA.17R, and a researcher at the Centre hospitalier universitaire de Québec in Canada, said: “A large proportion of women with early breast cancer are long-term survivors. As hormone therapy is given over a long period of time, measuring how women feel is very important.”