Breast Cancer Res Treat

Lobular histology and response to neoadjuvant chemotherapy in invasive breast cancer

Lips EH, Mukhtar RA, Yau C, de Ronde JJ, Livasy C, Carey LA, Loo CE, Vrancken-Peeters M-JTFD, Sonke GS, Berry DA, van t Veer LJ, Esserman LJ, Wesseling J, Rodenhuis S, Hwang ES, I-SPY 1 TRIAL Investigators

Invasive lobular carcinoma (ILC) has been reported to be less responsive to neoadjuvant chemother- apy (NAC) than invasive ductal carcinoma (IDC). We sought to determine whether ILC histology indeed predicts poor response to NAC by analyzing tumor characteristics such as protein expression, gene expression, and imaging features, and by comparing NAC response rates to those seen in IDC after adjustment for these factors. We com- bined datasets from two large prospective NAC trials, including in total 676 patients, of which 75 were of lobular histology. Eligible patients had tumors C3 cm in diameter or pathologic documentation of positive nodes, and underwent serial biopsies, expression microarray analysis, and MRI imaging. We compared pathologic complete response (pCR) rates and breast conservation surgery (BCS) rates between ILC and IDC, adjusted for clinico- pathologic factors. On univariate analysis, ILCs were sig- nificantly less likely to have a pCR after NAC than IDCs (11 vs. 25 %, p = 0.01). However, the known differences in tumor characteristics between the two histologic types, including hormone receptor (HR) status, HER2 status, histological grade, and p53 expression, accounted for this difference with the lowest pCR rates among HR?/HER2- tumors in both ILC and IDC (7 and 5 %, respectively). ILC which were HR- and/or HER2? had a pCR rate of 25 %.

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