Relative effectiveness of letrozole compared with tamoxifen for patients with lobular carcinoma in the BIG 1-98 Trial

Otto Metzger Filho, Anita Giobbie-Hurder, Elizabeth Mallon, Barry Gusterson, Giuseppe Viale, Eric P. Winer, Beat Thürlimann, Richard D. Gelber, Marco Colleoni, Bent Ejlertsen, Marc Debled, Karen N. Price, Meredith M. Regan, Alan S. Coates, Aron Goldhirsch

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose To evaluate the relative effectiveness of letrozole compared with tamoxifen for patients with nvasive ductal or lobular carcinoma Patients and Methods Patients diagnosed with early-stage invasive ductal carcinoma (IDC) or classic invasive lobular carcinoma (ILC) who were randomly assigned onto the Breast International Group (BIG) 1-98 tria and who had centrally reviewed pathology data were included (N = 2,923). HER2-negative IDC and LC were additionally classified as hormone receptor-positive with high (luminal B [LB] -like) or low (luminal A [LA] -like) proliferative activity by Ki-67 labeling index. Survival analyses were performed with weighted Cox models that used inverse probability of censoring weighted modeling Results The median follow-up time was 8.1 years. In multivariable models for disease-free survival (DFS), significant interactions between treatment and histology (ILC or IDC; P = .006) and treatment and subgroup (LB like or LA like; P = .01) were observed. In the ILC subset, there was a 66% reduction in the hazard of a DFS event with letrozole for LB (hazard ratio [HR], 0.34; 95% CI, 0.21 to 0.55) and a 50% reduction for LA subtypes (HR, 0.50; 95% CI, 0.32 to 0.78). In the IDC subset, there was a significant 35% reduction in the hazard of a DFS event with letrozole forthe LB subtype (HR, 0.65; 95% CI, 0.53 to 0.79), but no difference between treatments was noted for IDC and the LA subtype (HR, 0.95; 95% CI, 0.76 to 1.20) Conclusion The magnitude of benefit of adjuvant letrozole is greater for patients diagnosed with lobular carcinoma versus ductal carcinoma.

Original languageEnglish
Pages (from-to)2772-2778
Number of pages7
JournalJournal of Clinical Oncology
Volume33
Issue number25
DOIs
Publication statusPublished - Sep 1 2015

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

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