Abstract
Abstract
Background: Lobular carcinoma is the 2nd most common invasive breast cancer histology after ductal carcinoma. Though phenotypically they are different, the two histologies are often treated the same with presumed similar outcomes. We sought to compare the baseline demographics, standard pathologic factors and long term clinical outcomes between lobular and ductal carcinoma from a large population based breast cancer registry.Methods: A retrospective cohort of referred patients to the BCCA with a diagnosis of stage I-III pure lobular or pure invasive ductal carcinoma from 1989-2000 was identified. Prior or synchronous breast cancers and cases with unknown grade were excluded. Standard demographic and pathologic factors was abstracted from the BCCA Breast Cancer Outcomes Unit database and compared between the two histologies. 10 year outcomes were calculated by Kaplan Meier method, with differences compared by log rank test. Median follow up for the entire cohort was 9.3 years.Results: A total of 13,203 individual patients meeting identified inclusion criteria were identified: 11,911 invasive ductal and 1,292 invasive lobular cancers. Lobular carcinomas generally had a higher frequency of poor prognostic factors: older age (≥ 70 years old), larger tumour size, and greater frequency of N2 nodal involvement (all p<0.001). However lobular carcinomas also had a higher frequency of better predictive factors: ER+ status and low grade tumours (both p<0.001). There were differences in locoregional treatments and systemic therapies between the groups. No differences were seen at 10 year estimated relapse free survival (76% vs 74%), distant RFS (78% vs 77%), breast cancer specific survival (81% vs 81%) and overall survival (69% vs 70%) between lobular and ductal cancers respectively. Only 10 year locoregional RFS significantly favored lobular cancers (93% vs 89%; p<0.001), though there was also a higher mastectomy rate (55% vs 39%) in this cohort.Conclusion: Though invasive lobular carcinomas are epidemiologically and phenotypically different from ductal carcinomas, clinical outcomes are comparable between these two common histologies.
Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2046.