Abstract P2-10-10: Lower pathologic complete response rate with dual-HER2 blockage and chemotherapy in African Americans and ethnic minorities

Introduction: Racial disparities in breast cancer outcomes are well documented with age-adjusted mortality among African American (AA) women 40% higher than Caucasian women. Some studies have demonstrated poor response to neoadjuvant chemotherapy in AA with triple negative breast cancer but data regarding pathologic complete response rate (pCR) in HER2 positive disease are lacking. TRYPHAENA trial demonstrated a high pCR rate after treatment with dual HER2 blockage along with chemotherapy. Due to underrepresentation of African Americans and minorities in the trials leading to the approval of dual HER2 blockage (Gianni et al; Lancet Oncology;13: 25-32) in early stage breast cancer, data is lacking on the efficacy and tolerability of this treatment in this subgroup of patients. Methods: After IRB approval, pharmacy records were utilized to identify patients treated with dual HER2 blockade in neoadjuvant setting at our institution. Individual patient charts were reviewed to identify AA patients and other ethnic minorities. We also obtained details of the patient age, clinical stage, pathological stage, ER/PR status, treatment received, side effects leading to dose reductions if any. pCR was defined as absence of invasive or noninvasive cancer in the breast and lymph nodes (ypT0N0). Results:50 patients with a median age of 53 years met our inclusion criteria. 86% patients self-reported as AA and 14% were other minorities as recorded in EMR. 90% patients were treated with Taxotere, Carboplatin, Trastuzumab and Pertuzumab (TCHP) and 10% received Adriamycin, Cyclophosphamide, Paclitaxel, Trastuzumab and Pertuzumab (AC-THP) chemotherapy. Clinical staging was: Stage I- 4 %; Stage II- 84 %, and Stage III- 12 %. 46% of patients had hormone receptor (HR) positive tumors and 54% patients were HR negative. 30% (15/50) of patients required dose reduction or omission for diarrhea, neuropathy, or cytopenia. 18%(9/50) patients had doses omitted. The overall observed pCR rate (ypT0N0) was 42%(21/50). As expected, the pCR rate was higher in patients with HR negative/HER2 positive breast cancer compared to HR positive/HER2 positive breast cancer. 44% (12/27) vs. 39% (9/23), respectively.Conclusion: Dual HER2 blockade was associated with a lower pCR rate (42%) in AA and other minorities compared to rate of 52% as reported by TRYPHAENA trial (n=77). The treatment was well tolerated but higher percent of patients required a dose reduction or omission (Tiwari et al; Breast Cancer Res Treat; 158:189-193).The most common side effects were diarrhea, neuropathy and cytopenias. Further prospective studies are needed to elucidate the role of biologic differences in chemosensitivity and balancing the variables of increased number of dose reductions and effect of socioeconomic differences in an underserved minority population. Citation Format: Shruti R Tiwari, Prasun Mishra, Asma Dilawari, Christopher M Gallagher, Ami Chitalia, Patricia Wehner, Marc E Boisvert. Lower pathologic complete response rate with dual-HER2 blockage and chemotherapy in African Americans and ethnic minorities [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 P2-10-10.