Response pattern in 844 patients with infiltrating lobular carcinoma (ILC) of the breast after neoadjuvant chemotherapy.

Abstract

541 Background: Patients (pts) with infiltrating lobular carcinoma (ILC) have a different response to neoadjuvant chemotherapy compared to patients with non-lobular carcinoma (NLC). The aim of our analysis was to characterize correlates of the outcome impact of neoadjuvant chemotherapy in ILC and to compare those with NLC. Methods: Between 1998 and 2006; 6377 breast cancer patients were enrolled to 7 randomized neoadjuvant chemotherapy trials in Germany. For 6205 (98.3%) pts the histological type was available. 844 (13.6%) were classified as ILC, 5361 (86.4%) were classified as NLC. Endpoints of the analyses were: pathological complete response (pCR) defined as no invasive and no in-situ residuals in the breast and the lymph nodes, type of surgery, disease-free (DFS), local recurrence (LRFS) and overall survival (OS). Results: ILC was associated with older age, larger tumor size, negative nodes, lower grading, and hormone receptor (HR) positivity (all p<0.0001). The majority of pts with ILC were HR positive (717 pts, 86.9%) and had G1-G2 tumors (603 pts, 78.6%). Patients with ILC had a significant lower pCR rate than pts with NLC (pCR 6.04% vs. 16.4%, p<0.001). In the ILC group, pts with HR positive, triple-negative and HER2-positive tumors had a pCR rate of 5%, 18.3% and 9.2%, respectively. One of 35 pts with G1 and HR positive ILC had a pCR. Breast conservation therapy (BCT) in pts with pCR was 72.5% in the ILC group and 85.5% in the NLC group (p<0.0001). Predictors for pCR in the multivariate analysis were for ILC: patient age, grading and HR status. ILC pts had a significantly longer LRFS compared to NLC pts (with or without pCR after neoadjuvant chemotherapy, mean 112 months 95%CI [109.7-115.7] vs. 106 months 95%CI [104.4-107.4], p=0.002). Conclusions: In patients with ILC age, grading and HR status were predictive for pCR. Pts with ILC have a more favourable outcome after neoadjuvant chemotherapy despite a significantly lower pCR rate compared to pts with NLC.