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Relative Effectiveness of Letrozole Compared With Tamoxifen for Patients With Lobular Carcinoma in the BIG 1-98 Trial.

ABSTRACT: To evaluate the relative effectiveness of letrozole compared with tamoxifen for patients with invasive ductal or lobular carcinoma.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 trial and who had centrally reviewed pathology data were included (N = 2,923). HER2-negative IDC and ILC 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.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 for the 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).The magnitude of benefit of adjuvant letrozole is greater for patients diagnosed with lobular carcinoma versus ductal carcinoma.

SUBMITTER: Metzger Filho O

PROVIDER: S-EPMC4550691 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature

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Relative Effectiveness of Letrozole Compared With Tamoxifen for Patients With Lobular Carcinoma in the BIG 1-98 Trial.

Metzger Filho Otto O Giobbie-Hurder Anita A Mallon Elizabeth E Gusterson Barry B Viale Giuseppe G Winer Eric P EP Thürlimann Beat B Gelber Richard D RD Colleoni Marco M Ejlertsen Bent B Debled Marc M Price Karen N KN Regan Meredith M MM Coates Alan S AS Goldhirsch Aron A

Journal of clinical oncology : official journal of the American Society of Clinical Oncology 20150727 25

<h4>Purpose</h4>To evaluate the relative effectiveness of letrozole compared with tamoxifen for patients with invasive ductal or lobular carcinoma.<h4>Patients and methods</h4>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 trial and who had centrally reviewed pathology data were included (N = 2,923). HER2-negative IDC and ILC were additionally classified as h ...[more]

PMID: 26215945

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Project description:PurposeLuminal breast cancer has a long natural history, with recurrences continuing beyond 10 years after diagnosis. We analyzed long-term follow-up (LTFU) of efficacy outcomes and adverse events in the Breast International Group (BIG) 1-98 study reported after a median follow-up of 12.6 years.Patients and methodsBIG 1-98 is a four-arm, phase III, double-blind, randomized trial comparing adjuvant letrozole versus tamoxifen (either treatment received for 5 years) and their sequences (2 years of one treatment plus 3 years of the other) for postmenopausal women with endocrine-responsive early breast cancer. When pharmaceutical company sponsorship ended at 8.4 years of median follow-up, academic partners initiated an observational, LTFU extension collecting annual data on survival, disease status, and adverse events. Information from Denmark was from the Danish Breast Cancer Cooperative Group Registry. Intention-to-treat analyses are reported.ResultsOf 8,010 enrolled patients, 4,433 were alive and not withdrawn at an LTFU participating center, and 3,833 (86%) had at least one LTFU report. For the monotherapy comparison of letrozole versus tamoxifen, we found a 9% relative reduction in the hazard of a disease-free survival event with letrozole (hazard ratio [HR], 0.91; 95% CI, 0.81 to 1.01). HRs for other efficacy end points were similar to those for disease-free survival. Efficacy of letrozole versus tamoxifen for contralateral breast cancer varied significantly over time (0- to 5-, 5- to 10-, and > 10-year HRs, 0.62, 0.47, and 1.35, respectively; treatment-by-time interaction P = .005), perhaps reflecting a longer carryover effect of tamoxifen. Reporting of specific long-term adverse events seemed more effective with national registry than with case-record reporting of clinical follow-up.ConclusionEfficacy end points continued to show trends favoring letrozole. Letrozole reduced contralateral breast cancer frequency in the first 10 years, but this reversed beyond 10 years. This study illustrates the value of extended follow-up in trials of luminal breast cancer.

Dataset Information

Relative Effectiveness of Letrozole Compared With Tamoxifen for Patients With Lobular Carcinoma in the BIG 1-98 Trial.

Publications

Relative Effectiveness of Letrozole Compared With Tamoxifen for Patients With Lobular Carcinoma in the BIG 1-98 Trial.

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