148P The impact of chemotherapy relative dose intensity on pathological complete response and event-free survival in patients with triple-negative breast cancer treated with neoadjuvant chemotherapy

Neoadjuvant chemotherapy (NACT) is the preferred approach for treating early-stage triple-negative breast cancer (TNBC). Pathologic complete response (pCR) after NACT is associated with prolonged survival in patients (pts) with TNBC. Reliable predictive biomarkers for pCR are still needed. We therefore investigated the value of relative dose intensity (RDI) of chemotherapy in predicting pCR. A retrospective analysis was conducted on 221 pts with early-stage TNBC receiving NACT between February 2018 and October 2023 at the University of Naples Federico II and at the Humanitas Clinical Institute of Catania, Italy. Delivered versus planned chemotherapy (CT) dose intensity (RDI) ratio was categorized as low (<85%) or high (≥85%). The relationship between tumor stage, RDI, CT regimen dose type and pCR were evaluated by univariate and multivariate logistic regression analyses and event-free survival (EFS) curves according to RDI by Kaplan-Meier and log-rank tests. The median age at diagnosis was 51 years (range 28-75 years). Among the 221 pts, 166 (75%) had stage II, and 55 (25%) had stage III TNBC. Seventy-seven (35%), 145 (65%), and 52 (23%) pts received a dose-dense (dd) CT schedule, carboplatin, and pembrolizumab, respectively. Overall, 138 (62%) and 83 (38%) pts received a high and low RDI, respectively. No significant differences in tumor and patient characteristics, as well as in type of treatment regimens were observed between the two groups. The median study follow-up was 31 months. At univariate analysis, RDI high was significantly associated with pCR (OR 3.13, 1.65-5.91, p < 0.001). Moreover, RDI independently predicted pCR (OR 3.39, 95% CI: 1.77-6.5, p < 0.001) and EFS (HR, 0.38; 95% CI, 0.20 to 0.67, p = 0.003) in a multivariate model including RDI, tumor stage, use of pembrolizumab and carboplatin, and administration of dose-dense CT. Regardless the type and schedule of NACT, RDI high is associated with increased pCR rates and prolonged EFS in pts with early-stage TNBC. If confirmed by further studies our results support a meticolous routine RDI monitoring during neoadjuvant treatment for TNBC in clinical practice.