Preventing relapse beyond 5 years: the MA.17 extended adjuvant trial

Area of Science:

• Oncology
• Endocrinology
• Clinical Trials

Background:

• Adjuvant tamoxifen for hormone-receptor-positive breast cancer has limitations, with significant relapse risk after 5 years.
• Extended tamoxifen use is not recommended, highlighting the need for alternative strategies.
• Aromatase inhibitors offer potent estrogen synthesis inhibition for postmenopausal women with early-stage breast cancer.

Purpose of the Study:

• To evaluate the efficacy of extended adjuvant letrozole therapy after 5 years of tamoxifen.
• To determine if letrozole improves disease-free survival in postmenopausal women with early-stage breast cancer.

Main Methods:

• MA.17 trial: a large, randomized, double-blind, placebo-controlled phase III study.
• Participants: Postmenopausal women with hormone-receptor-positive or unknown early-stage breast cancer.
• Intervention: Extended adjuvant therapy with letrozole versus placebo after ~5 years of tamoxifen.

Main Results:

• Letrozole significantly reduced breast cancer recurrence risk by 42% and distant metastasis by 40%.
• Overall survival improved significantly in node-positive patients, with a 39% reduction in mortality.
• Letrozole was well-tolerated, with bone metabolism effects being the most notable side effect.

Conclusions:

• Extended adjuvant letrozole therapy is effective and well-tolerated for preventing breast cancer recurrence post-tamoxifen.
• Updated MA.17 results support letrozole as a valuable option for high-risk patients.
• Further insights into long-term benefits and risks are expected from ongoing patient re-randomization.