Abstract 35: Racial disparity in localized breast cancer: Pooled analysis of NSABP trials
Authors: Kim Gina , Pastoriza Jessica M. , Qin Jiyue , Lin Juan , Karagiannis George S. , Condeelis John S. , Yothers Greg , Julian Thomas B. , Anderson Stewart J. , Entenberg David , Rohan Thomas E. , Sparano Joseph A. , Xue Xiaonan , Oktay Maja H. 
Published: July 2021

Background: The purpose of this study was to evaluate whether there are differences in distant recurrence rates between Black and White women with localized breast cancer who participated in NCI-sponsored clinical trials, and thus had access to state of the art oncologic care and lacked major comorbidities.

Methods: We analyzed pooled data from 10 NSABP trials including 10,364 patients with localized breast cancer treated with adjuvant chemotherapy (AC, n=8147) or neoadjuvant chemotherapy (NAC, n=2217), limited to those with self-reported race that was either Black (n=1006, 10.3%) or White (n=9358, 89.7%). AC/NAC included doxorubicin and cyclophosphamide, with or without a taxane. The association between race (Black vs. White) and distant relapse-free survival (DRFS) was analyzed in the overall population and stratified by AC or NAC use. Log rank tests were used to test for differences in DRFS. Multivariate Cox regression was performed to estimate risk of distant recurrence adjusted for other prognostic covariates including age (continuous), tumor size (&gt; 2 cm vs. &lt; 2 cm), ER expression (positive vs. negative), and nodal status (pathologically positive for AC cohort or clinically positive for NAC cohort vs. negative).

Results: In the AC cohort, 7,419 (91%) patients were White and 728 (9%) Black. In the NAC cohort, 1,939 (88%) were White and 278 (12%) Black. Black race was associated with an inferior DRFS in the combined AC/NAC cohort (Logrank p&lt;.0001), and in both the AC and NAC cohorts (Logrank p=0.0008 and p=0.01, respectively). After adjustment for other covariates in multivariate analysis, Black race remained significantly associated with an inferior DRFS in the combined AC/NAC cohort (HR 1.17, [95% CI 1.05-1.31], p=0.004), with similar trends noted in the AC (HR 1.17 [95% CI 1.02-1.33], p=0.03) and NAC cohort (HR 1.21 [95% CI 0.98-1.45], p=0.08). When the AC cohort was analyzed by ER status, Black race was associated with worse DRFS in ER-positive disease (HR 1.32 [95% CI 1.06-1.63], p=0.02), but not ER-negative disease (HR 1.06, [95% CI 0.87-1.30], p=0.57), although there was no statistically significant interaction with ER status (p=0.15). In the NAC cohort, Black women had a higher pathologic complete response (pCR) rate (22% vs 17%, Chi-squared test p=0.03). Black race was associated with a significantly worse DRFS in patients who did not achieve pCR (HR 1.34 [95% CI 1.06-1.63], p=0.01), but not in those who had a pCR (HR 0.89 [95% CI 0.49, 1.61], p=0.71).

Conclusion: We observed that Black women with localized breast cancer had higher distant recurrence rates than White women. This and other reports suggest that factors other than social determinants of health may be contributing to racial disparities in breast cancer outcome/progression, most notably in ER-positive disease and patients with residual disease after NAC. Future research is needed to help delineate the biological differences that contribute to these observations.

Citation Format: Gina Kim, Jessica M. Pastoriza, Jiyue Qin, Juan Lin, George S. Karagiannis, John S. Condeelis, Greg Yothers, Thomas B. Julian, Stewart J. Anderson, David Entenberg, Thomas E. Rohan, Joseph A. Sparano, Xiaonan Xue, Maja H. Oktay. Racial disparity in localized breast cancer: Pooled analysis of NSABP trials [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 35.