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JCO Early Release, published online ahead of print Mar 10 2008
Received August 15, 2007 Benefit From Exemestane As Extended Adjuvant Therapy After 5 Years of Adjuvant Tamoxifen: Intention-to-Treat.Analysis of the National Surgical Adjuvant Breast and Bowel Project B-33 Trial
From the National Surgical Adjuvant Breast and Bowel Project Operations and Biostatistical Centers; Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh; Allegheny General Hospital; Shadyside Hospital, University of Pittsburgh; University of Pittsburgh Cancer Institute, Magee-Womens Hospital, Pittsburgh, PA; Aultman Health Foundation, Canton, OH; University of California at Los Angeles, Jonsson Comprehensive Cancer Center, Los Angeles; Scripps Clinic, San Diego; Kaiser Permanente Northern California, Vallejo, CA; Ohio State University, Columbus, OH; CCOP Southeast Cancer Control Consortium, Winston-Salem, NC; CCOP Colorado Cancer Research Program, Denver, CO; Arkansas Cancer Research Center, Little Rock, AK; Toronto Sunnybrook Regional Cancer Center, North York, Ontario; Centre Hospitalier de l'Université de Montréal, Québec, Canada; CCOP Marshfield Clinic, Marshfield, WI; and the Mayo Clinic, Rochester, MN. * To whom correspondence should be addressed. E-mail: tmamounas{at}aultman.com
Purpose: Patients with early-stage, hormone receptor-positive breast cancer have considerable residual risk for recurrence after completing 5 years of adjuvant tamoxifen. In May 2001, the National Surgical Adjuvant Breast and Bowel Project (NSABP) initiated accrual to a randomized, placebo-controlled, double-blind clinical trial to evaluate the steroidal aromatase inhibitor exemestane as extended adjuvant therapy in this setting. Patients and Methods: Postmenopausal patients with clinical T1-3N1M0 breast cancer who were disease free after 5 years of tamoxifen were randomly assigned to 5 years of exemestane (25 mg/d orally) or 5 years of placebo. Our primary aim was to test whether exemestane prolongs disease-free survival (DFS). In October 2003, results of National Cancer Institute of Canada (NCIC) MA.17 showing benefit from adjuvant letrozole in this setting necessitated termination of accrual to B-33, unblinding, and offering of exemestane to patients in the placebo group. Results: At the time of unblinding, 1,598 patients had been randomly assigned; 72% in the exemestane group continued on exemestane and 44% in the placebo group elected to receive exemestane. With 30 months of median follow-up, original exemestane assignment resulted in a borderline statistically significant improvement in 4-year DFS (91% v 89%; relative risk [RR] = 0.68; P = .07) and in a statistically significant improvement in 4-year relapse-free survival (RFS; 96% v 94%; RR = 0.44; P = .004). Toxicity, assessed up to time of unblinding, was acceptable for the adjuvant setting. Conclusion: Despite premature closure and crossover to exemestane by a substantial proportion of patients, original exemestane assignment resulted in non-statistically significant improvement in DFS and in statistically significant improvement in RFS.
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Copyright © 2008 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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