Abstract P1-10-16: Ethnicity, recurrence score (RS) distribution, and clinical outcomes in ER+ HER2-negative breast cancer (BC) patients (pts) in Israel
Authors: Sela Gil Bar , Samih Yousef , Yerushalmi Rinat , Leviov Michelle , Ben-Baruch Noa Efrat , Kuchuk Iryna , Tokar Margarita , Peretz Tamar , Sonnenblick Amir L , Soussan-Gutman Lior , Bareket-Samish Avital , Fried Georgeta , Paluch-Shimon Shani , Kaufman Bella , Hammerman Ariel , Liebermann Nicky , Stemmer Salomon M 
Published: March 2020

Background: The RS assay is widely used in ER+ HER2-negative BC to guide treatment decisions. In TAILORx, RS distribution was similar in blacks vs whites and in Hispanics vs non-Hispanics. Also, TAILORx analyses revealed similar results across ethnic groups with endocrine therapy being consistently noninferior to chemotherapy (CT) plus endocrine therapy in RS 11-25 pts. We investigated RS distribution among Jewish vs Arab/Druze pts who underwent RS testing through Clalit Health Services (CHS), the largest HMO in Israel, as well as differences in CT use and clinical outcomes between these 2 ethnic groups.

Methods: The RS distribution analysis included all CHS pts (regardless of nodal status) who were tested between 1/2006 and 2/2019. For the clinical outcomes analysis, we employed a dataset used in prior analyses (Stemmer et al, poster# 249, SG-BCC 2019) of node-negative pts who were tested between 1/2006 and 12/2009, and as such, it is a subset of the cohort used for the RS distribution analysis. The study was approved by the IRB of the CHS Community Division and was granted a waiver for obtaining pt consent.

Results: The RS distribution analysis involved 9054 pts who were tested in the evaluated timeframe and for whom RS results and ethnicity information were available. These included 8223 (91%) Jews and 831 (9%) Arabs/Druze, approximately reflecting the proportion of BC cases diagnosed in the respective ethnic groups. The 2 groups were similar in their baseline pt/tumor characteristics except for age and tumor size (Table). RS distribution was also similar between the 2 ethnic groups (Table). The subset of node-negative pts for whom treatment and clinical outcomes are known included 1274 (93%) Jewish pts and 91 (7%) Arab/Druze pts. In this subset, the only statistically significant difference in pt/tumor characteristics between the ethnic groups was age (median [interquartile range]) of 60 [53-66] yrs in the Jewish pts vs 55 [48-63] yrs in the Arab/Druze pts; P=.0004), similar to the complete cohort. The RS distribution was similar to that in the larger cohort, with no significant differences between the ethnic groups (P=.75). Also, CT use was consistent with the RS result in both ethnic groups, and was overall somewhat higher among Arab/Druze pts (25% vs 19%), due primarily to higher CT use among Arabs/Druze pts in the largest RS category (11-25), in which significant differences with respect to age were noted (median [interquartile range], 59 [52-66] yrs in Jewish pts vs 52 [46-61] yrs in Arab/Druze pts; P&lt;.0001). CT use was 0%, 9%, and 69% in Jewish pts with RS 0-10, 11-25, and 26-100, respectively, whereas in Arab/Druze pts, the respective CT use was 0%, 14%, and 75%. At 10 years, clinical outcomes (all RS groups combined) were similar in the ethnic groups; 10-year breast cancer-specific mortality was 3.7% (95% CI, 2.6-5.3%) for Jewish pts and 4.4% (95% CI, 1.4-13.2%) for Arab/Druze pts.

Conclusions: RS distribution and clinical outcomes were similar in Jewish and Arab/Druze BC pts. Arab/Druze pts undergoing RS testing were overall younger than the Jewish pts, which may suggest under-diagnosis and/or under-testing in the older Arab/Druze pt population. Also, CT use seemed higher in the Arab/Druze pt population, possibly reflecting the differences in the age distribution between these ethnic groups.

Table: Patient/tumor characteristics by ethnicityJewsArabs/DruzeP valuen = 8223n = 831Female, n (%)8132 (98.9%)825 (99.3%).3Median (interquartile range) age, years62 (53-68)55 (48-64)&lt;.0001Nodal status, n (%).14Node-negative5974 (72.6%)583 (70.2%)N1mi552 (6.7%)52 (6.3%)1-3 positive nodes1506 (18.3%)180 (21.7%)≥4 positive nodes18 (0.2%)2 (0.2%)Unknown173 (2.1%)14 (1.7%)Median (interquartile range) tumor size in the greatest dimension, cm2.0 (1.2-2.2)1.8 (1.4-2.5)&lt;.0001Tumor size category, n (%)&lt;.0001≤1 cm1714 (20.8%)112 (13.5%)&gt;1 - 2 cm4233 (51.5%)411 (49.5%)&gt;22153 (26.2%)302 (36.3%)Unknown123 (1.5%)6 (0.7%)Tumor grade category, n (%).12Grade 11109 (13.4%)123 (14.8%)Grade 24192 (51.0%)443 (53.3%)Grade 31389 (16.9%)120 (14.4%)Not applicable/Unknown1533 (18.6%)145 (17.4%)Histology, n (%).92IDC6530 (79.4%)665 (80.0%)ILC1113 (13.5%)113 (13.6%)Papillary79 (1.0%)10 (1.2%)Mucinous/colloid144 (1.8%)16 (1.9%)Other/unknown357 (4.3%)27 (3.2%)Recurrence Score category, n (%).170-101612 (19.6%)176 (21.2%)11-255091 (61.9%)522 (62.8%)26-1001520 (18.5%)133 (16.0%)

Citation Format: Gil Bar Sela, Yousef Samih, Rinat Yerushalmi, Michelle Leviov, Noa Efrat Ben-Baruch, Iryna Kuchuk, Margarita Tokar, Tamar Peretz, Amir L Sonnenblick, Lior Soussan-Gutman, Avital Bareket-Samish, Georgeta Fried, Shani Paluch-Shimon, Bella Kaufman, Ariel Hammerman, Nicky Liebermann, Salomon M Stemmer. Ethnicity, recurrence score (RS) distribution, and clinical outcomes in ER+ HER2-negative breast cancer (BC) patients (pts) in Israel [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-10-16.