Comparison of triple negative (TN) and HER2 positive (HER2+) invasive lobular carcinomas (ILCs) to a matched cohort of invasive ductal carcinomas.

Abstract

e13088Background: Most ILCs are estrogen receptor (ER) positive and tend to relapse at different sites than IDCs, suggesting distinct biology. We explored prognosis for TN and HER2+ ILCs and IDCs. Methods: From the prospective British Columbia (BC) Cancer Outcomes Unit database, we identified TN and HER2+ ILCs diagnosed 01/2003 to 12/2013 referred to BC Cancer. Exclusions: stage IV, mixed ILC/IDC, unknown HER2, and prior / subsequent breast cancer. ILCs were propensity-score matched (1:2) to IDCs for age, T/N stage, biomarkers, grade, chemotherapy (CT), and nodal radiation (RT). Kaplan-Meier method was used to estimate relapse-free survival (RFS) and overall survival (OS). Results: Of 2925 ILCs diagnosed, 2587 were referred, and 143 were TN or HER2+. By comparison, there were 5526 TN and HER2+ IDCs. After exclusions, 127 TN and HER2+ cases (23% TN; 77% HER2+) were matched as shown in Table 1. Five-year RFS was ILCs 81% (95% confidence interval [CI], 73-87%) and IDCs 84% (95% CI, 79-88%). Five-year OS was ...