Original Study The Effect of Total Size of Lesions in Multifocal/Multicentric Breast Cancer on Survival Yusuf Karakas, 1 Omer Dizdar, 1 Sercan Aksoy, 1 Mutlu Hayran, 1 Kadri Altundag 2 Abstract Multifocal/multicentric (MF/MC) breast cancer was identified about 10% of all breast cancer. Approximately 4000 breast cancer patients were evaluated and it was found that the MF/MC breast cancer was better T stage classified and more predictive according to T sum which is the sum of the longest diameters of the lesions. This is more prominent in MF/MC patients with low disease burden. Background: In this study, we aimed to assess the prognostic performance of determining the T stage according to the total size of lesions compared with the size of the largest lesion in the breast in patients with multifocal/mul- ticentric (MF/MC) breast cancer. Patients and Methods: The charts of the patients with MF/MC breast cancer who were diagnosed between 2003 and 2014 were reviewed. The T stage of MF/MC tumors was determined according to the largest lesion size (T max ) as well as the sum of the longest diameters of the lesions (T sum ) in the breast. Results: Multifocal/multicentric tumors were identified in 323 of 3890 patients (8.3%) with breast cancer. Ten-year rates of overall survival (OS; 75% and 74%; P ¼ .965) and disease-free survival (DFS; 66% and 61%; P ¼ .817) were similar in patients with unifocal and MF/MC tumors, respectively. When the T stage was determined by summing the sizes of the lesions, the T stage of 67 (20.7%) and 63 (19.5%) patients advanced from T1 to T2 and from T2 to T3, respectively. Thus, the T stage increased in 130 patients (40.2%) according to American Joint Committee on Cancer. Discriminatory ability of T sum was better than T max in terms of OS and DFS, as shown with higher Royston D and Harrel C statistics and Schemper V values. Conclusion: The new T classification proposed in this report stands out as a better predictive classification particularly in patients with low disease burden. Clinical Breast Cancer, Vol. -, No. -, --- ª 2017 Elsevier Inc. All rights reserved. Keywords: Multicentricity, Multifocality, Staging, T classification, Unifocal Introduction Multifocal (MF) and multicentric (MC) are descriptors to define the presence of more than 1 focus of tumor in the same breast, within the same quadrant (MF) or within different quadrants (MC). The incidence of MF/MC breast cancer ranges from 4% to 50%. 1,2 The effect of MC and MF breast cancer on survival is not well characterized. In some studies, multifocality itself does not appear to be a contributing factor for worse outcome. 3 The American Joint Committee on Cancer (AJCC) staging guidelines recommend the greatest dimension of the tumor to be used to stage the disease for MF/MC tumors, and when multiple tumors are present, this is denoted by suffixing the T stage with “m” (for example, T2m). This has no effect on overall staging category. 4 However, the largest unidimensional measurement might not be representative of the total breast tumor burden in patients with MF/MC disease. 5 In this study, we investigated and compared the prognostic value of determining the T stage according to summation of diameters of the lesions or according to the size of the largest lesion alone in patients with MF/MC breast cancer. Patients and Methods In this retrospective single-center study, we analyzed data from 3890 patients with breast cancer at the department of medical oncology at Hacettepe University between 2003 and 2014. We assessed patient and tumor characteristics including age, menopausal status, TNM stage, histologic subtype, Grade, lymphatic and vascular invasion, hormone receptor (HR) and c-erb-B2 expression, and all therapies. Tumor classification as unifocal, MF, or MC was determined according to pathology reports. Tumors were classified 1 Hacettepe University Cancer Institute, Ankara, Turkey 2 Mustafa Kadri Altundag (MKA) Breast Cancer Clinic, Ankara, Turkey Submitted: Jul 14, 2017; Revised: Sep 28, 2017; Accepted: Nov 2, 2017 Address for correspondence: Kadri Altundag, MD, MKA Breast Cancer Clinic, Tepe Prime, Cankaya, 06800 Ankara, Turkey Fax: þ90-312-2854685; e-mail contact: altundag66@yahoo.com 1526-8209/$ - see frontmatter ª 2017 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.clbc.2017.11.002 Clinical Breast Cancer Month 2017 - 1