Adjuvant letrozole provides more benefit to patients with lobular carcinoma compared with those with ductal carcinoma, according to an article published online ahead of print in the Journal of Clinical Oncology.
The purpose of this study was to evaluate the 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 carnoma (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).
Patients were further characterized as hormone receptor-positive with high (luminal B [LB]-like) or low (luminal A [LA]-like) proliferative activity. Survival analyses were performed using weighted Cox models that used inverse probability of censoring weighted modeling.
Median follow-up was 8.1 years. Interactions between treatment and histology were observed (ILC or IDC; P=0.006) as well as treatment and subgroup (LB like or LA-like; P=0.01).
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Patients in the IDC subset showed a 66% reduction in the hazard of a disease-free survival event with letrozole for LB and a 50% reduction for LA subtypes.
In the IDC subset, there was a significant 35% reduction in the hazard of a disease-free survival event with letrozole for the LB subtype, but no difference between treatment arms was noted for IDC and LA subtype.
- Filho OM, Giobbie-Hurder A, Mallon E, et al. Relative effectiveness of letrozole compared with tamoxifen for patients with lobular carcinoma in the BIG 1-98 trial. J Clin Oncol. 2015. [epub ahead of print]. doi: 10.1200/JCO.2015.60.8133.