Abstract P2-09-13: 21 Gene Recurrence Scores: Racial Differences in Testing, Scores, Treatment, and Outcome
Authors: Lund MJ , Mosunjac M , Davis KM , Gabram SGA , Rizzo M , Okoli J , Bumpers HL , Zelnak A , Hearn S , Styblo T , O'Regan RM. 
Published: April 2011

BACKGROUND: African American (AA) women experience higher breast cancer mortality than white (W) women, partly attributable to their development of poor prognosis tumors and differences in access and treatment. However mortality differences persist among estrogen receptor positive (ER+) breast cancers, despite similar stage and treatment. The 21-gene recurrence score (RS) assay (Oncotype DX) is used to determine optimal individualized treatment in patients with ER+, node negative (N-) breast cancer. Results are reported on a continuum and also trichotomized into 3 RS groups: low(0-18), intermediate(19-31) and high(&gt;31), the latter most likely benefitting from chemotherapy, achieving less benefit with hormonal therapy, and exhibiting lower ER levels (intrinsically categorized as luminal B cancers). We investigated differences between AA and W women in RS, treatment, and outcome.

METHODS: Tumor registry data from three Atlanta hospitals identified female invasive breast cancers of AA or W descent diagnosed during 2005-2009. Additional medical record abstraction obtained information on RS, treatment, and outcome. Statistical analyses employed chi-square, fisher exact, t-tests, and multivariate logistic regression. RESULTS: Of 1987 cases (AA=1110, W=877), 773 were identified as Stage I-II, ER+N-, thus eligible for RS testing [AA=350(45.3%), W=423 (54.7%), P&lt;0.0001]; 170 (22.2%) of those received RS testing [AA=47(13.4%), W=123(29.1%), P&lt;0.0001]. Patients distributed into the following risk groups: Low=91, Medium=63, High=16; mean(median) RS=19.0(17.0), range=0-69.

Neither mean RS (AA=20.4, W=18.5, p=0.287) nor risk groups (Low=51.1% vs 54.5%, Medium=34.0% vs 38.2%, and High=14.9% vs 7.3% for AA and W women respectively, p=0.333) significantly differed by race. However, AA women were more likely than W women to be diagnosed under age 50 (40.4% vs 23.5%, p=0.036) with higher prevalence of tumors of larger size (Mean = 2.0 cm vs 1.6cm, p=0.038) and Grade III (23.4% vs 8.1%, p=0.0.026), and stage II disease (38.3%% vs 23.6%, p=0.057). Only grade and tumor size were associated with RS in multivariate analyses.

After median follow-up of 20 months (range 1-55), 5 women recurred (2AA, 3W); 2 low, 2 intermediate, and 1 high risk. Chemotherapy was received by 40 women (Low=7, Medium=19, High=14) and did not differ by race (AA=31.9%, W=20.3%, p=0.156). Hormonal therapy was received by 80.5% of W and 63.8% AA women (p=0.027). DISCUSSION: AA women were less likely than W women to be diagnosed with ER+N-breast cancers and to receive RS testing if diagnosed. Of those tested, RS scores did not significantly differ by race. However, AA women tended to have poorer prognostic factors. Our data suggest that testing guidelines are not equivalently applied, that selection bias in testing could be attenuating any real racial differences in RS, and that disparate outcomes could partly be explained by treatment differences, treatment effectiveness e.g. endocrine agent metabolism, compliance, as well as differences in prognostic factors; all areas requiring future exploration.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-13.