Invasive micropapillary breast cancer: Single-institution experience in the modern era.

Abstract

150 Background: Invasive micropapillary breast cancer (IMPC) is a rare special histologic type of breast cancer with a propensity for nodal metastases. Molecularly, IMPCs have been classified as luminal B; however, clinical outcome data in the era of targeted therapy are limited. Here we report our institutional experience with IMPC. Methods: We retrospectively reviewed our prospective database from 1995-2009 to identify patients who had surgery for IMPC. Clinical characteristics and outcomes were abstracted from the medical record. Overall survival (OS) was estimated using Kaplan-Meier methods. Factors associated with OS and trends over time were assessed using the log-rank test and Cox regression. Results: We identified 258 patients with IMPC. Median patient age 56yrs (range 26-91), 157(61%) postmenopausal, 147(57%) presented with a palpable mass. The majority of IMPCs were grade 3 (83%), estrogen receptor (ER)-positive (86%) and HER2-neg (81%) with LVI (60%) and nodal metastasis (62%). 194 (75%) patients received chemotherapy (CTX), 204 (81%) hormonal therapy and 37/48 (77%) HER2-pos patients received trastuzumab. At a median follow-up of 55 months (range 1-173mos), 5yr OS is 89.5% with a trend towards improved survival in later yrs; 5 year OS 1995-2005 vs 2006-2009, 85% vs 91%, respectively (p=0.06) Clinical factors associated with OS are shown (Table). Among ER-pos/HER2-neg patients, progesterone receptor (PR) status was strongly associated with 5yr OS. Conclusions: In this large cohort of patients with IMPC treated at a single center, OS was associated with tumor size, PR status, use of CTX and trastuzumab but not with ER or hormonal therapy. These clinical data support the molecular classification of IMPC as luminal B cancers which have a more aggressive clinical behavior than other ER+ cancers. The trend towards improved survival in later years likely reflects the benefits of targeted therapy. [Table: see text]