Ten-year update: NRG Oncology/National Surgical Adjuvant Breast and Bowel Project B-42 randomized trial: extended letrozole therapy in early-stage breast cancer

Author:

Mamounas Eleftherios P1ORCID,Bandos Hanna2,Rastogi Priya34,Lembersky Barry C3,Jeong Jong-Hyeon2,Geyer Charles E3,Fehrenbacher Louis5,Chia Stephen K6,Brufsky Adam M4,Walshe Janice M7,Soori Gamini S8,Dakhil Shaker R9,Wade James L10,McCarron Edward C11,Swain Sandra M12,Wolmark Norman2

Affiliation:

1. Department of Surgical Oncology, Orlando Health Cancer Institute , Orlando, FL, USA

2. NRG Oncology SDMC, and the Department of Biostatistics, University of Pittsburgh , Pittsburgh, PA, USA

3. University of Pittsburgh Medical Center Hillman Cancer Center, Department of Oncology, University of Pittsburgh School of Medicine , Pittsburgh, PA, USA

4. Department of Oncology, University of Pittsburgh Magee-Womens Hospital , Pittsburgh, PA, USA

5. Department of Medical Oncology, Kaiser Permanente Oncology Clinical Trials Northern California , Novato, CA, USA

6. Department of Medical Oncology, British Columbia Cancer Agency (BCCA) , Vancouver, British Columbia, Canada

7. Department of Oncology, Cancer Trials Ireland (formerly known as Irish Clinical Oncology Research Group—ICORG) , Dublin, Ireland

8. Department of Oncology, Florida Cancer Specialists , Fort Myers, FL, USA

9. Department of Oncology, Community Clinical Oncology Program, Wichita via Christi Regional Medical Center , Wichita, KS, USA

10. Department of Oncology, Decatur Memorial Hospital, Cancer Care Specialists of Illinois, Heartland National Cancer Institute Community Oncology Research Program , Decatur, IL, USA

11. Department of Surgical Oncology, MedStar Franklin Square Medical Center at Weinberg Cancer Institute , Baltimore, MD, USA

12. Department of Surgical Oncology, Georgetown Lombardi Comprehensive Cancer Center, MedStar Health , Washington, DC, USA

Abstract

Abstract Background The National Surgical Adjuvant Breast and Bowel Project B-42 trial evaluated extended letrozole therapy (ELT) in postmenopausal breast cancer patients who were disease free after 5 years of aromatase inhibitor (AI)–based therapy. Seven-year results demonstrated a nonstatistically significant trend in disease-free survival (DFS) in favor of ELT. We present 10-year outcome results. Methods In this double-blind, phase III trial, patients with stage I-IIIA hormone receptor–positive breast cancer, disease free after 5 years of an AI or tamoxifen followed by an AI, were randomly assigned to 5 years of letrozole or placebo. Primary endpoint was DFS, defined as time from random assignment to breast cancer recurrence, second primary malignancy, or death. All statistical tests are 2-sided. Results Between September 2006 and January 2010, 3966 patients were randomly assigned (letrozole: 1983; placebo: 1983). Median follow-up time for 3923 patients included in efficacy analyses was 10.3 years. There was statistically significant improvement in DFS in favor of letrozole compared with placebo (hazard ratio [HR] = 0.85, 95% confidence interval [CI] = 0.74 to 0.96; P  = .01; 10-year DFS: placebo = 72.6%, letrozole = 75.9%, absolute difference = 3.3%). There was no difference in the effect of letrozole on overall survival (HR = 0.97, 95% CI = 0.82 to 1.15; P  = .74). Letrozole statistically significantly reduced breast cancer–free interval events (HR = 0.75, 95% CI = 0.62 to 0.91; P = .003; absolute difference in cumulative incidence = 2.7%) and distant recurrences (HR = 0.72, 95% CI = 0.55 to 0.92; P = .01; absolute difference = 1.8%). The rates of osteoporotic fractures and arterial thrombotic events did not differ between treatment groups. Conclusions The beneficial effect of ELT on DFS persisted at 10 years. Letrozole also improved breast cancer–free interval and distant recurrences without improving overall survival. Careful assessment of potential risks and benefits is necessary for selecting appropriate candidates for ELT.

Funder

National Cancer Institute

National Institutes of Health

US Department of Health and Human Services, Public Health Service

Korea Health Technology R&D

Korean Health Industry Development Institute

Ministry of Health and Welfare, Republic of Korea

Publisher

Oxford University Press (OUP)

Subject

Cancer Research,Oncology

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