Abstract GS1-02: Racial disparity in tumor microenvironment and outcomes in residual breast cancer treated with neoadjuvant chemotherapy

Background: Black, compared to White women with localized breast cancer have higher mortality and worse distant recurrence free survival (DRFS). This has been attributed to social determinants of health and higher prevalence of triple negative breast cancer (TNBC) in Black compared to White women. Recent studies indicate that racial disparity in outcome is present in patients with estrogen receptor-positive (ER+), but not ER- disease, in particular in patients with residual disease after neoadjuvant chemotherapy (NAC). It has been shown that in some patients NAC may induce pro-metastatic changes in tumor microenvironment, such as increased density of tumor associated macrophages and portals for cancer cell dissemination to distant sites called TMEM doorways (TMEM score). TMEM score correlates with metastasis in patients with ER+/HER2- breast cancer. We hypothesized that racial disparity in DRFS in patients with residual ER+/HER2- disease is due to enhanced pro-metastatic components (macrophage and TMEM doorway density) in the tumor microenvironment post-chemotherapy in Black compared to White women.

Methods: We performed a retrospective, multi-institutional study of TMEM score and macrophage density in the residual disease after NAC from 196 patients diagnosed with unilateral invasive ductal cancer of breast between 2004 and 2014. 99 patients self-identified as Black and 97 as White. TMEM doorways were visualized by triple immunohistochemistry for macrophages (CD68), tumor cells (panMena), and endothelial cells (CD31). The evaluation of TMEM score and macrophage density was done using automated image analysis. Tumor characteristics and patient survival were compared between Black and White patients. The relationship between TMEM score, macrophage density and DRFS was examined by log-rank test and multivariate Cox regression model. The covariates in Cox model included TMEM score, age (continuous), race (Black vs White), surgery type (mastectomy vs lumpectomy), tumor stage (T3 vs T1; T2 vs T1), lymph node status (positive vs negative), and tumor subtype (triple negative [TN] vs ER+/HER2-; other vs ER+/HER2-).

Results: Black compared to White women were more likely to develop distant recurrence (49.5% vs 34%, p=0.04), receive mastectomy (69.7% vs 51.5%, p=0.014), and have higher grade (p=0.001). Tumors from Black patients had more macrophages and a higher TMEM score in the entire cohort (p=0.004; p=0.001 respectively) and in the ER+/HER2- subset (p=0.008; p=0.008 respectively), but not in the TNBC subset. High TMEM score was associated with worse DRFS in all patients (p=0.004) and in the ER+/HER2- (p=0.03), but not in TNBC. In multivariate Cox model, TMEM score was an independent prognostic factor in the entire cohort (HR, 1.92; 95%CI, 1.15-3.22; p=0.01) and trended towards significance in ER+/HER2- disease (HR, 2.13; 95%CI, 0.96-4.71; p=0.06). TN, compared to ER+/HER2- cancers had higher TMEM score (p=0.01), and macrophage density (p=0.001).

Conclusion: Racial disparity in outcome in patients with localized breast cancer may be due to a more pronounced pro-metastatic response to chemotherapy in Black, compared to White patients with ER+/HER2- disease. Thus, higher prevalence of TNBC in Black patients may not be the controlling factor in racial disparity.

Citation Format: Burcu Karadal, Gina Kim, Ved Sharma, Jessica Pastoriza, Isabelle Oktay, Yu Lin, Xianjun Ye, Jiyue Qin, Esther Cheng, Nurfiza Ladak, John Condeelis, Esther Adler, Paula Ginter, Timothy D’Alfonso, Xiaonan Xue, David Enterberg, Joseph Sparano, Maja Oktay. Racial disparity in tumor microenvironment and outcomes in residual breast cancer treated with neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS1-02.