Abstract P5-10-02: African Americans have more aggressive invasive lobular carcinoma subtypes and inferior early outcomes: SEER 2010-2013
Authors: Thomas A , Altekruse S , Avery TP , Melin SA , Howard-McNatt MM , Schroeder MC 
Published: March 2017

Abstract
Introduction:
African Americans (AA) present more frequently with triple negative breast cancer (TN) and other aggressive breast cancer subtypes. Invasive lobular (ILC) breast cancer most commonly presents as estrogen receptor (ER)+, progesterone receptor (PR)+ and HER2-, though less frequently the more aggressive ER- or PR- luminal, TN or HER2+ subtypes occur. For women presenting with ILC 2010-2013, we report by race, differences in disease subtype, grade and stage at presentation and 2-year outcomes.
Methods:
We conducted a retrospective cohort analysis using Surveillance, Epidemiology and End Results Program. Women diagnosed with first primary malignant lobular breast cancer from 2010-2013 were included. Subtypes were categorized into four exclusive groups: ER+ and PR+ HER2-, ER+ or PR+ HER2-, TN and HER2+. Two-year survival was compared across race, and a multivariate cox model assessed overall survival.
Results:
ILC occurred less frequently in non-whites (Table 1). AA and other non-whites were younger at diagnosis than whites (p&lt;0.001). AAs and other non-whites were less likely to have ER+ and PR+ HER2- disease (OR 0.85, p= 0.019 and OR 0.79, p=0.003 respectively). AAs had ILC of significantly higher grade and presented with more advanced stage disease than other race categories (p&lt;0.001 for both). On multivariate analysis, survival was inferior for AA relative to whites (HR 1.32, p&lt;0.010). Other non-whites had better survival than whites (HR 0.58, p=0.008). For AAs 2-year survival by disease subtype was: ER+ and PR+ HER2- (91.3%), ER+ or PR+ HER2- (90.5%), TN (59.5%), HER2+ (84.0%). For these subtypes, the proportion of women presenting with Stage IV ILC was 8.1%, 10.8%, 22.6% and 15.9% respectively.
Conclusion:
In this large, recent ILC cohort there were significant racial disparities in disease biology at presentation, with non-whites having more aggressive ILC subtypes, but only AAs having higher grade ILC. Short-term survival outcomes were inferior for AAs. Whether AAs presenting with advanced stage disease more frequently is due to biology or access to care is unknown. Further study of disease biology and healthcare delivery disparities could offer improved outcomes for AAs with ILC.
Table 1: ILC Characteristics by Race WhiteAA Other non-white N13,5571,445 957 ILC - % diagnoses per race category9.67.2 5.8 Rate of ILC (per 100,000 women of that race)10.56.4 4.4 Median Age6461 60 %%OR*p%OR*pSubtype ER+ and PR+ HER2-80.978.30.850.01977.00.790.003ER+ or PR+ HER2-12.914.41.140.10615.31.220.036TN1.52.11.440.0642.11.400.158HER2+4.75.11.090.4735.61.210.186Stage I40.536.4 39.0 &lt;0.001II36.534.5 40.4 III17.019.9 14.9 IV6.09.2 5.6 Grade (Differentiation) Well or Moderate91.287.5 89.5 &lt;0.001Poor or Undifferentiated8.812.5 10.5 2-year survival93.9%90.0% 96.3% *compared to white (reference group)
Table 2: Multivariate Cox Model for 2-year Survival HRp95% CIRace Whiteref AA1.320.0101.071.64Other non-white0.580.0080.380.87Subtype ER+ and PR+ HER2-ref ER+ or PR+ HER2-1.80&lt;0.0011.512.16TN2.89&lt;0.0012.074.03HER2+0.970.8670.691.37Stage Iref II1.91&lt;0.0011.512.42III3.44&lt;0.0012.714.37IV22.34&lt;0.00117.7828.07Grade (Differentiation) Well or Moderateref Poor or Undifferentiated1.400.0011.141.71
Citation Format: Thomas A, Altekruse S, Avery TP, Melin SA, Howard-McNatt MM, Schroeder MC. African Americans have more aggressive invasive lobular carcinoma subtypes and inferior early outcomes: SEER 2010-2013 [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-10-02.