Abstract PO2-16-09: Dose-dense versus 3-weekly AC during Neoadjuvant Chemoimmunotherapy for Early-Stage Triple-Negative Breast Cancer (TNBC): a Real-World Safety and Efficacy Data Analysis

Abstract Background: The Keynote-522 (KN-522) study established the use of pembrolizumab in combination with neoadjuvant carboplatin-paclitaxel, followed by 3-weekly (3w) anthracycline-cyclophosphamide (AC), as the standard of treatment for stage II-III TNBC. However, dose-dense chemotherapy (CT) improves survival rates compared to the standard schedule in early-stage breast cancer and several groups have been modifying the KN-522 regimen with dose-dense AC (ddAC). The objective of this study was to compare the safety and effectiveness of ddAC versus the q3w schedule. Methods: We conducted a multicentric real-world analysis of patients (pts) with early-stage TNBC who received neoadjuvant CT plus pembrolizumab at nine cancer centers. Safety endpoints included grade ≥ 3 adverse events (AEs), drug discontinuation, hospitalization due to AEs, and the use of antibiotics during neoadjuvant therapy. Pathologic complete response (pCR) was used as the effectiveness endpoint, and we performed univariate and multivariable logistic regression to evaluate factors associated with pCR. Results: To date, we included 168 pts in this study of which 137 pts have finished the neoadjuvant therapy phase and constituted our safety cohort. Among them, 86 pts (62.8%) received ddAC and 51 pts (37.2%) were treated with the 3w schedule. The two groups exhibited no significant differences in baseline characteristics; the median age was 42 years (range 29 - 75), 70.8% had stage II and 25.5% had stage III TNBC, 46.7% had positive lymph nodes, and 74.4% had a Ki67-index ≥ 50%. Overalls, 30.2% and 27.4% presented grade ≥ 3 AEs with ddAC and 3w AC, respectively, with no significant difference between the two groups (p=0.177). Grade ≥ 3 immune-related AEs (irAEs), occurred in 8.1% with ddAC and 3.9% with 3w AC (0.335). The most common grade ≥ 3 irAEs were pneumonitis (n=4) and hepatitis (n=2). The ddAC group had a higher rate of any drug discontinuation due to toxicities (24.4% vs. 11.8%, p=0.043) and a greater use of antibiotics (27.9% vs. 11.8%, p=0.009) compared to the 3w group. There was a trend toward more rates of hospitalization due to AEs in the ddAC group, although this was not statistically significant (17.4% vs 11.8%, p=0.131). At the time of data analysis cutoff, a total of 119 pts underwent surgery and have pathology report available and were included in the efficacy cohort. In the univariate analysis, the pCR rates were 65.8% with ddAC and 55.8% with 3w AC (OR 1.52, 95% CI 0.70-3.27, p=0.282). The rates of RCB (residual cancer burden) 0-1 were 81.2% and 67.6%, respectively (OR 2.06, 95% CI 0.82 – 5.16, p=0.120). Factors influencing rates of pCR were Ki67 index ≥ 50% and tumor staging, which remained significant in the multivariable analysis (Table). In the 3w AC group, no difference in pCR was observed between pts who used or not granulocyte colony stimulating-factors (61.1% vs 52%, p=0.553). Conclusion: No difference in grade ≥ 3 AEs was observed between ddAC and 3w AC in pts with early-stage TNBC receiving neoadjuvant CT plus pembrolizumab. Nevertheless, the dose-dense regimen was linked to higher rates of drug discontinuation and antibiotic use. Although the pCR rates numerically favored ddAC, the difference was not statistically significant. Thus, the medical community should consider carefully risks and benefits of using ddAC within the KN522 regimen. Larger studies and longer follow-up are warranted to assess the long-term outcomes of the CT schedules. Multivariable regression of factors associated with pCR Citation Format: Renata Colombo Bonadio, Fernanda Madasi, José Bines, Rafael Ferreira, Daniela Rosa, Candice Santos, Zenaide Souza, Daniele Assad-Suzuki, Julio Araujo, Débora Gagliato, Carlos dos Anjos, Bruna Zucchetti, Anezka Ferrari, Mayana Lopes, Renata Cangussu, Maria Marcela Monteiro, Paulo Hoff, Laura Testa, Romualdo Barroso-Sousa. Dose-dense versus 3-weekly AC during Neoadjuvant Chemoimmunotherapy for Early-Stage Triple-Negative Breast Cancer (TNBC): a Real-World Safety and Efficacy Data Analysis abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-16-09.