P2-14-03: A Comparison of Biologic Differences in Tumors in a Matched Cohort of Hispanic and Caucasian Women with Early-Stage Breast Cancer Using the 21-Gene Recurrence Score Assay.
Authors: Lim EA , Hershman DL , Greenlee H , Crew KD , Maurer MA , Hibshoosh H , Kalinsky K 
Published: June 2012

Background: Several studies demonstrate that Hispanic women have a higher mortality rate and lower incidence of breast cancer (BC) as compared to Caucasian women. This survival pattern has also been observed in Hispanic women with untreated, early-stage BC. The Hispanic population should be considered a heterogeneous group, however, given the various racial and national backgrounds that comprise this entity. As African American (AA) similarly demonstrate a worse survival as compared to Caucasian women, a retrospective analysis of 27 tumor from AA patients (pts) showed a significantly higher expression of the 5 proliferation genes in the 21-gene recurrence score (RS) assay (Oncotype Dx) as compared to other races, with no significant difference observed in the 21-gene RS. The primary aim of this analysis is to investigate biologic differences between Hispanic women in a primarily Dominican Republic population, as compared to Caucasian women, as determined by indices in the 21-gene RS assay.

Methods: We collected data from women with early-stage breast cancer who underwent RS assay testing between 2005 and 2011. Pt charts were reviewed for ethnicity (Hispanic or other), country of origin, RS, 10-year risk of distant recurrence, and breast tumor ER/PR/HER2 expression by Oncotype Dx. Hispanic pts were matched to Caucasians in a 1:2 fashion based on age (+/− 10 years), tumor stage, and presence of lymph node metastases. Prognostically important clinicopathologic features were collected, including lymphovascular invasion (LVI) and grade. Descriptive statistics were computed. Two Sample t-testing was used to evaluate if RS was equal across by ethnicity groups.

Results: Of 214 pts who underwent RS testing, 30 (13.5%) were Hispanic: 18 from the Dominican Republic, 5 from Puerto Rico, and 1 from various Central and South American populations. The 30 Hispanic women were matched to 57 Caucasians: total population 87 pts. The mean RS for Caucasian women was 18.3 (range: 0–54) and for Caucasians: 15.5 (range: 1–38). By two Sample t test, no statistically different differences were observed between Hispanic and Caucasian women in regards to the RS (p= 0.2828) or 10-year distant recurrence score after 5 years of anti-estrogen therapy (p=0.4218). No differences were observed in median ER expression (9.4% vs. 10.1%: Hispanic vs. Caucasian), PR (7.2% vs. 7.7%), or HER2 (9.2% vs. 9.0%). LVI was numerically more frequently identified in Hispanic pts [7/30 (23.3%) vs. 8/57 (14.0%)], as were grade III tumors [7/30 (23.3%) and 4/57 (7%)].

Conclusions: Similar to the findings with AA pts, there was no significant difference in RS between Hispanic and matched Caucasian women with early-stage BCs. A numerical trend to a higher RS was seen in this Hispanic population of primarily pts from the Dominican Republic. We will evaluate for differences in the 5 genes involved in proliferation (CCNB1, MKI17, MYBL2, BIRC5, AURKA). Also, further analyses will be conducted with additional pts to determine if the numeric differences in RS, LVI, and grade are observed in a larger cohort.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-14-03.