Abstract P6-06-35: Invasive lobular cancer versus mixed invasive lobular cancer with invasive ductal cancer: 20 year outcomes at one institution
Authors: Wallace AS , Xiang D , Hockman L , Arya M , Jeffress J , Wang Z , Dale PS 
Published: August 2014

Abstract
Introduction: Conflicting reports exist regarding characteristics and outcomes of patients with only invasive lobular carcinoma (ILC) and mixed invasive lobular and ductal carcinoma (ILC/IDC). The purpose of this project is to report experience of 20 year cohort at one institution.
Methods: Patients diagnosed with ILC between 1990 and 2010 were divided into two groups: ILC alone and ILC/IDC. Patient demographics, history, diagnosis and treatment modalities, and outcomes were captured. Chi-square, log-rank, and Wilcoxon rank sums tests were utilized for statistical analysis. P &lt; 0.05 was considered significant.
Results: In 189 AJCC Stage I-III patients, ILC was identified in 149 (79%) and ILC/IDC in 39 (21%). ILC stage was I, II, III in 46 (31%), 57 (41%), 32 (21%) ILC, and ILC/IDC was 17 (44%), 16 (41%), 4 (10%). Median age (range) at diagnosis was 64 (31-88) for ILC and 64 (35-84) years for ILC/IDC (p = 0.78). Median largest tumor diameter was 22 (range 1-100) in ILC, and 20 (range 2-110) mm in ILC/IDC (p = 0.97). Seventy-eight (52%) and 20 (51%) were diagnosed with ILC and ILC/IDC clinically, and 58 (39%) and 15 (38%) were diagnosed with ILC and ILC/IDC radiographically (p = 0.96). Treatment modalities were mastectomy and breast conservation therapy in 82(55%) and 67(45%) of patients with ILC, 18 (46%) and 21 (54%) of patients with ILC/IDC (p = 0.32). In 136 (91%) ILC and 33 (85%) ILC/IDC patients who had nodal evaluation/excision, 59 (43%) ILC and 12 (36%) ILC/IDC patients presented with positive nodal status. ER, PR, and HER2 status were positive in 132 (89%), 104 (70%), 7 (5%) ILC, and 29 (74%), 26 (67%), 3 (8%) ILC/IDC patients respectively (p = 0.02, p = 0.85, p = 0.17).
Median (range) follow-up for ILC was 6.1 (&lt; 1-22.3), and 8.0 (1.72-17.7) years for ILC/IDC (p = 0.03). At the time of analysis, 43(29%) patients with ILC, and 11(28%) patients with ILC/IDC had expired (p = 0.94). Median (range) follow-up for patients who were alive at time of analysis was 6.8 (&lt;1-20.7) years for ILC, and10.1 (2.3-17.7) years for ILC/IDC (p = 0.06). Time to first recurrence was 3.23 (0.8-17.0) years in ILC, and 5.2 (2.9-9.3) years in ILC/IDC (p = 0.20). Recurrence was identified in 33(22%) ILC: 15(46%) locoregional and18 (54%) distant disease. Similarly, recurrence was found in 7 (20%) ILC/IDC patients: 4 locoregional and 3 distant. Most locoregional recurrences, 12/15 (80%), occurred in the ipsilateral breast in ILC, and 3/4 (75%) in ILC/IDC (p = 0.82). Five years disease free survival rates were 76% ILC and 85% for ILC/IDC, and 10 years rates were 63% for ILC and 67% for ILC/IDC (p = 0.4941). Overall survival estimates at 5 years were 84% for ILC and 92% for ILC/IDC, and at 10 years were 65% for ILC and 74% for ILC/IDC (p = 0.52).
Conclusion: While basic demographics and survival patterns did not differ statistically between ILC and ILC/IDC, pure ILC histology tends to carry a higher risk of recurrence, as well as worse disease free and overall survival compared to ILC/IDC. ILC histology was more likely to be ER positive, present with advanced stage, and recur in the ipsilateral breast than the contralateral breast.
Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-35.