Classifying invasive lobular carcinoma as special type breast cancer may be reducing its treatment success: A comparison of survival among invasive lobular carcinoma, invasive ductal carcinoma, and no-lobular special type breast cancer

PURPOSE: The literature contains different information about the prognosis of invasive lobular carcinoma of breast cancer (BC). We aimed to address the inconsistency by comparatively examining the clinical features and prognosis of invasive lobular carcinoma patients in our university and to report our experience by dividing our patients into various subgroups. PATIENTS AND METHODS: Records of patients with BC admitted to Trakya University School of Medicine Department of Oncology between July 1999 and December 2021 were reviewed. The patients were divided into three groups (No-Special Type BC, Invasive Lobular Special Type BC, No-Lobular Special Type BC). Patient characteristics, treatment methods and oncological results are presented. Survival curves were generated using the Kaplan–Meier method. Statistical significance of survival among the selected variables was compared by using the log-rank test. RESULTS: The patients in our study consisted of 2142 female and 15 male BC patients. There were 1814 patients with No-Special Type BC, 193 patients with Invasive Lobular Special Type BC, and 150 patients with No-Lobular Special Type BC. The duration of disease-free survival (DFS) was 226.5 months for the No-Special Type BC group, 216.7 months for the No-Lobular Special Type BC group, and 197.2 months for the Invasive Lobular Special Type BC group, whereas the duration of overall survival (OS) was 233.2 months for the No-Special Type BC group, 227.9 for the No-Lobular Special Type BC group, and 209.8 for the Invasive Lobular Special Type BC group. The duration of both DFS and OS was the lowest in the Invasive Lobular Special Type BC group. Multivariate factors that were significant risk factors for OS were Invasive Lobular Special Type BC histopathology (p = .045), T stage, N stage, stage, skin infiltration, positive surgical margins, high histological grade, and mitotic index. Modified radical mastectomy, chemotherapy, radiotherapy and use of tamoxifen and aromatase inhibitors for more than 5 years were significant protective factors for overall survival. CONCLUSION: The histopathological subgroup with the worst prognosis in our study was Invasive Lobular Special Type BC. Duration of DFS and OS were significantly shorter in Invasive Lobular Special Type BC than No-Lobular Special Type BC group. The classification of Invasive Lobular BC under the title of Special Type BC should be reconsidered and a more accurate treatment and follow-up process may be required.