Invasive lobular carcinoma classic type: Response to primary chemotherapy and survival outcomes

Purpose: To investigate the impact of histologic type invasive lobular carcinoma (ILC) versus invasive ductal carcinoma (IDC) on response to primary chemotherapy (PC) and long-term outcome. Patients and Methods: The study included 1,034 patients with stage II and III breast cancer who participated in six clinical trials of PC at our institution between 1985 and 2002. One hundred twenty-two patients (12%) had ILC and 912 (88%) had IDC. All patients received anthracycline-based PC, and 346 patients (33.5%) also received a taxane as part of PC. Pathologic complete response (pCR) was defined as no evidence of invasive disease in the breast and axillary lymph nodes. Results: The median patient age was 48 years (range, 18 to 79 years). Patients with ILC tended to be older (median age, 53 years v 47 years for patients with IDC) and have more hormone-receptor-positive tumors (92% v 62%; P < .001), lower nuclear grade (nuclear grade 3, 16% v 56%; P < .001), and higher stage at diagnosis (10% v 0% with stage IIIB or IIIC disease; P < .001). Patients with ILC were less likely to have a pCR (3% v 15%; P < .001) and had a larger number of involved axillary lymph nodes (41% v 26% had > 3 involved nodes; P = .001). At a median follow-up time of 70 months, ILC patients tended to have longer recurrence-free survival (P = .004) and overall survival (P = .001). Conclusion: ILC is characterized by lower rates of pathologic response to PC but better long-term outcomes compared to IDC. pCR might not be a prognostic indicator for this group of patients.