Comparison of Outcome between Invasive Lobular Carcinoma (ILC) and Invasive Ductal Carcinoma (IDC) Patients Treating with Breast Conserving Surgery (BCS) and Radical Dose of Intraoperative Electron Radiotherapy (IOERT)

Background: Invasive lobular carcinoma (ILC) differs from invasive ductal carcinoma (IDC) in genomic profile, clinicopathologic behavior, and response to treatment. Despite favorable profile, ILC is susceptible to recurrence. Thus, most of studies did not include ILC in intraoperative radiotherapy (IORT) trials or considered it as a cautionary criteria, especially in accelerated partial breast irradiation (APBI). Objectives: In this study, we compared treatment outcome between breast cancer patients with ILC and IDC treating with breast conserving surgery and intraoperative electron radiotherapy (IOERT). Methods: A total of 191 patients with early breast cancer treated with breast conserving surgery and IOERT were included in the study. This study compared outcome of 42 ILC patients with 135 IDC patients. Fourteen patients were mixed type. ILC was a suitable criterion, as well. Local recurrence and disease-free survival were endpoints of study. Results: Median follow-up was 23.17 month and 21.17 month for IDC and ILC, respectively. Univariate analysis was done according to age, pathologic, and biologic factors and multivariate analysis was according molecular subtype. There were 3 patients with local recurrence. Two patients were in the IDC group and another one was the ILC group. There was no significant difference between two groups. The 4-year disease-free survival (DFS) was 95.45% and 97.40% for ILC and IDC, respectively. Conclusions: In this study, there was no significant difference in in-breast tumor recurrence (IBTR) and DFS between two groups. It was seem lobular carcinoma can be used for APBI and it may be a suitable criterion as the IDC.