Primary results, NRG Oncology/NSABP B-35: A clinical trial of anastrozole (A) versus tamoxifen (tam) in postmenopausal patients with DCIS undergoing lumpectomy plus radiotherapy.

Breast Cancer—HER2/ER
Session Type and Session Title: 
Oral Abstract Session, Breast Cancer—HER2/ER
Abstract Number: 


J Clin Oncol 33, 2015 (suppl; abstr LBA500)
Richard G. Margolese, Reena S. Cecchini, Thomas B. Julian, Patricia A. Ganz, Joseph P. Costantino, Laura Vallow, Kathy S. Albain, Pat W. Whitworth, Mary E. Cianfrocca, Adam Brufsky, Howard M. Gross, Gamini S. Soori, Judith O. Hopkins, Louis Fehrenbacher, Keren Sturtz, Timothy F. Wozniak, Thomas E. Seay, Eleftherios P. Mamounas, Norman Wolmark; NRG Oncology/NSABP, and The Jewish General Hospital, McGill University, Montréal, QC, Canada; NRG Oncology, and the University of Pittsburgh, Pittsburgh, PA; NRG Oncology/NSABP, and The Allegheny Cancer Center at Allegheny General Hospital, Pittsburgh, PA; NRG Oncology/NSABP, and the University of California, Los Angeles, Los Angeles, CA; NRG Oncology/NSABP, ALLIANCE/NCCRT, and Mayo Clinic, Jacksonville, FL, Jacksonville, FL; NRG Oncology/NSABP, SWOG, and Loyola University Chicago Stritch School of Medicine, Maywood, IL; NRG Oncology/NSABP, ALLIANCE/ACOSOG, and Nashville Breast Center, Nashville, TN; ECOG/ACRIN, SWOG, and Banner MD Anderson Cancer Center, Gilbert, AZ; NRG Oncology/NSABP, and Magee Women's Hospital, Pittsburgh, PA; NRG Oncology/NSABP, and Hem and Onc Div of Dayton Physicians LLC, Dayton, OH; NRG Oncology/NSABP, and Nebraska Cancer Specialists, Omaha, NE; NRG Oncology/NSABP, and SCOR NCORP and the Forsyth Regional Cancer Center, Winston Salem, NC; NRG Oncology/NSABP, and Kaiser Permanente Northern California, Novato, CA; Colorado Cancer Research Program, Denver, CO; NRG Oncology/NSABP, and CCOP, Christiana Care Health Systems, Newark, DE; NRG Oncology/NSABP, and the Atlanta Regional Community Clinical Oncology Program, Atlanta, GA; NRG Oncology/NSABP and UF Cancer Center at Orlando Health, Orlando, FL; NRG Oncology/NSABP, and the Allegheny Cancer Center at Allegheny General Hospital, Pittsburgh, PA

Abstract Disclosures


Background: The primary endpoint of NSABP B-35, a phase III trial comparing 1 mg/day anastrozole to 20 mg/day tamoxifen, each given for 5 years, was breast cancer-free interval (BCFI), defined as the time from randomization to any breast cancer (BC) event including local, regional, or distant recurrence or contralateral disease, invasive or DCIS. Methods: Postmenopausal women with ER-receptor or PgR-receptor positive (by IHC analysis) DCIS and no invasive BC who had undergone a lumpectomy with clear resection margins were randomly assigned to receive either 20 mg/day tam or 1 mg/day A (blinded) for 5 years. Stratification was by age (<60 v ≥60). Results: From 1/6/2003 to 6/15/2006, 3,104 pts were entered and randomized (1552 in groups tam and A each). As of 2/28/15, follow-up information was available on 3,083 pts for OS and on 3,077 pts for all other disease-free endpoints, with mean time of follow-up of 8.6 years. There were 198 BCFI events, 114 in the tam group and 84 in the A group (HR, 0.73; p=0.03). 10-year point estimates for BCFI were 89.2% for tam and 93.5% for A. A significant time-by-treatment interaction (p=0.02) indicated that the effect was not evident until later in the study. There was a significant interaction between treatment and age group (p=0.04); benefit of A is only in women <60 years old. As to secondary endpoints, there were 495 DFS events, 260 in the tam group and 235 in the A group (HR, 0.89; p=0.21). 10-year point estimates for DFS were 77.9% for tam and 82.7% for A. There were 186 deaths, 88 in the tam group and 98 in the A group (HR, 1.11; p=0.48). 10-year point estimates for OS were 92.1% for tam, 92.5% for A. There were 8 deaths due to breast cancer in the tam group and 5 in the A group. There were 63 cases of invasive breast cancer in the tam group and 39 in the A group (HR, 0.61; p=0.02). There was a non-significant trend for a reduction in breast second primary cancers with A (HR, 0.68; p=0.07). Conclusions: Anastrozole provided a significant improvement compared to tamoxifen for BCFI, which was seen later in the study, primarily in women <60 years. Support: CA12027, 37377, 69651, 69974; 180868, 180822, 189867 196067, 114732; AstraZeneca Pharmaceuticals LP. Clinical trial information: NCT00053898