Abstract P4-14-10: Breast cancer histolological subtypes by race/ethnicity
Authors: Parise Carol , Caggiano Vincent 
Published: May 2015

Abstract
BACKGROUND
It is generally accepted that Asian/Pacific Islanders with breast cancer have the same or better survival than whites. Infiltrating duct carcinoma (IDC) is the most common histologic subtype of breast cancer but little is known about whether this subtype varies by race/ethnicity. The purpose of this study was to determine if there was a difference in incidence of IDC among different race/ethnicities.
METHODS
We identified 197,570 cases of AJCC stages 1-4 first primary female invasive breast cancer from the California Cancer registry 2000-2011. The race/ethnicity distribution was as follows: Whites n=130,634; Blacks n=11,927; Hispanics n=32,291; Asian/Pacific Islanders (API) n=22,027; and American Indians n= 691. Histology was classified using ICDO-3. The distribution of infiltrating ductal, infiltrating lobular, mixed ductal/lobular, mucinous, tubular, and medullary cancer was examined using contingency tables and Pearson Residuals. Odds ratios were computed for infiltrating ductal versus all other histologies for each race/ethnicity using whites as the comparator with logistic regression analysis adjusting for age, stage, socioeconomic status, grade, and ER/PR/HER2. The stage X race interaction was tested.
RESULTS
Whites had fewer than expected cases of IDC (z = -8.5) and APIs had more than expected (z = 9.2). Blacks (z = 5.6) and Hispanics (z = 6.1) had a higher number of IDC cases than expected and also had a higher than expected number of cases of medullary (black: z=12.8; Hispanic: z =10.7). The proportion of American Indians with each of the subtypes was similar to what would be expected.
The stage X race interaction was statistically significant so analyses were conducted separately for each stage. APIs had an increased risk of IDC in all stages except for stage 4. Hispanics had an increased risk in stage 3 but a decreased risk in stage 4. American Indians had the same risk as whites for all stages. Blacks had decreased odds of IDC in stage 1 but increased odds in stage 3. (Table 1)
Table 1. Odds ratios and 95% confidence intervals of infiltrating duct carcinoma from the California Cancer Registry 2000-2011. WhiteBlackHispanicAsian/Pacific IslanderAmerican Indian OR (95% CI)OR (95% CI)OR (95% CI)OR (95% CI)OR (95% CI)Stage 11.000.90 (0.81, 0.99)0.98 (0.92, 1.05)1.20 (1.12,1.29)1.31 (0.89, 1.92)Stage 21.000.99 (0.90, 1.09)1.06 (1.00, 1.14)1.39 (1.29, 1.50)0.73 (.051, 1.02)Stage 31.001.27 (1.10, 1.48)1.24 (1.12, 1.37)1.74 (1.52, 1.99)1.02 (0.59, 1.76)Stage 41.001.02 (0.79, 1.31)0.78 (0.64, 0.94)1.21 (0.94, 1.56)0.48 (0.19, 1.19)Confidence intervals that include 1.00 indicate that the odds of IDC were no different than the reference category
CONCLUSION
The incidence of IDC is not the same for all race/ethnicities and depends on the stage of disease. APIs are at an increased risk for IDC in all except for the highest stage of disease.
Citation Format: Carol Parise, Vincent Caggiano. Breast cancer histolological subtypes by race/ethnicity [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-14-10.