Real-world outcomes of neoadjuvant chemo-immunotherapy in triple-negative breast cancer at a safety-net institution.

e12715 Background: The addition of immunotherapy to neoadjuvant chemotherapy for stage II-III triple negative breast cancer (TNBC) has been shown to significantly improve pathologic complete response (pCR) rates and patient survival. However, the applicability of these results to real-world populations with varying ethnic and socioeconomic backgrounds is unclear. We sought to evaluate neoadjuvant treatment outcomes of TNBC patients treated at a safety net institution in Los Angeles County (48% Hispanic.). Methods: This is a retrospective cohort study of patients with TNBC treated at a safety-net hospital between 2020 and 2025 who received neoadjuvant chemoimmunotherapy per KEYNOTE 522 regimen. Patients who did not receive surgery were excluded. Primary outcomes included pCR, primary refractory disease, and disease relapse. Outcomes were compared between Hispanic and non-Hispanic patients. An exploratory analysis evaluated the association between Ki-67 expression and treatment response. Overall rates of pCR, primary refractory disease, and relapse were calculated with exact 95% confidence intervals using binomial methods. Categorical outcomes were compared between groups using Fisher’s exact test. Ki-67 was compared across outcome groups (pCR vs no pCR, refractory vs responders, relapse vs no relapse) using the Wilcoxon rank-sum test. All analyses were two-sided, with statistical significance set at p < 0.05, and performed using R. Results: The overall pCR rate was 54.5% (12/22; 95% CI 32.2–75.6%). pCR rate in Hispanics was 47.1% (8/17) vs 80.0% (4/5) in non-Hispanics (p = 0.32). The overall primary refractory rate was 27.3% (6/22; 95% CI 10.7–50.2%) with 35.3% (6/17) in Hispanics vs 0% (0/5) in non-Hispanics (p = 0.27). Overall relapse rate was 9.1% (2/22; 95% CI 1.1–29.2%) with 11.8% (2/17) in Hispanics vs 0% (0/5) in Non-Hispanics (p = 1.00). Patients who achieved pCR had a higher Ki-67 vs those who did not (75% vs 60%, p = 0.14). Treatment refractory patients had a lower Ki-67 vs treatment responders (45% vs 70% p = 0.18). There was not enough data to calculate the association between relapse and Ki-67. Conclusions: KEYNOTE-522 established neoadjuvant chemoimmunotherapy as the standard of care in high risk early stage TNBC, demonstrating higher pCR rates (64.8%) than chemotherapy alone. However, Hispanics were underrepresented in the trial population. In our real-world cohort, the pCR rate was lower (54.5%) with Hispanics patients achieving pCR (47.1%) less frequently than non-Hispanics (80.0%). Rates of primary refractory disease and relapse were also higher among Hispanic patients. Interpretation of subgroup comparisons is limited by the small number of non-Hispanic patients. These findings highlight the need for further investigation and inclusion of ethnically diverse patient populations to better understand factors influencing treatment response and recurrence risk.