Long-Term Hormone Therapy Decreases Breast Cancer Recurrence

Postmenopausal women with early breast cancer showed a reduction in disease recurrence after 10 years of aromatase inhibitor therapy with letrozole.

The phase 3 clinical trial MA.17R found that postmenopausal women with early breast cancer had a reduction in disease recurrence after 10 years of hormonal therapy.

Findings from 2 related abstracts (LBA1 — Plenary and LBA506) from the MA.17R trial were presented at the American Society of Cancer Oncology (ASCO) Annual Meeting.

Researchers enrolled 1918 postmenopausal women who received 5 years of one of the aromatase inhibitor (AI) therapies, before initial treatment or after any duration of prior tamoxifen. Patients could enroll in the study up to 2 years after completing AI therapy, but approximately 90% started letrozole (Femara) or placebo within 6 months of completed therapy.

The goal of LBA1 — Plenary was to determine safety and efficacy outcomes. Women in the extended Femara group saw a 34% lower risk of breast cancer recurrence.

Additionally, the annual incidence of contralateral breast cancer was found lower in the Femara arm (0.21%) compared with the placebo arm (0.49%). In the Femara group, 95% of patients were breast cancer-free at the 5-year follow-up, while 91% of patients who received the placebo were cancer-free.

The 5-year overall survival rate was not statistically significant, at 93% for the placebo group and 94% for the Femara group.

LBA506 sought to find the quality of life outcomes, with the findings showing no significant differences in overall quality of life and menopause-specific quality of life in women who took Femara for 5 years or who received the placebo.

There were small differences found in the physical role functioning in favor of the placebo, but these were not considered clinically meaningful.

“Women with early-stage hormone-receptor positive breast cancer face an indefinite risk of relapse,” said lead study author Paul Goss, MD, FRCP, PhD. “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.”