31P Peripheral-blood Immune-predictors of pathological complete response in patients with triple-negative breast cancer undergoing neoadjuvant chemo-immunotherapy

Background: Pathological complete response (pCR) is the strongest patient-level prognostic factor in patients with early triple-negative breast cancer (TNBC) undergoing neoadjuvant chemo-immunotherapy (NAT).Blood-based biomarkers have been proposed to recapitulate the immune-milieu and to anticipate benefit from NAT.We explored correlations between pCR and immune-inflammatory indices such as neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), granulocytestimulating factors (G-CSF) use, all having demonstrated to be prognostic in the metastatic setting.Methods: We retrospectively collected data from all consecutive patients who completed NAT with pembrolizumab (KEYNOTE-522 regimen) from Jan 2022 until Aug 2024, from our single-institution cohort.Logistic regression was performed to investigate the association between pCR and NLR or PLR at baseline (0), at the switch from taxane-to anthracycline-based chemo (5) and at the end of the NAT (8).Odds ratios (OR), 95% confidence intervals (CI), and p-values were calculated with alpha set at 0.05.Results: Of the 43 patients included in the study, 49% were diagnosed with stage IIB, achieving a pCR in 61% of these cases.The OR for the NLR0 was 0.90 (95% CI: 0.57e 1.42, p0.665), for NLR5 was 0.74 (p0.190) and for NLR8 was 0.86 (p0.421),indicating no significant predictive value for pCR.Similarly, PLR0 (OR: 0.99, p0.623) and PLR5 (OR: 0.99, p0.139) also showed no significant association; the use of G-CSF was not independently prognostic.When examining combined models including G-CSF and NLR values, no statistical significance was observed; the combination of G-CSF and NLR5 yielded an OR of 0.72 (95% CI: 0.45e1.16,p0.184).Conclusions: Our research evaluated the longitudinal trend of NLR or PLR in the NAT setting.We did not find evidence to support the use of NLR or PLR (at different timepoints) as predictive biomarkers of pCR with NAT in patients with early TNBC, mainly due to the low statistical power.Future studies with larger sample sizes and additional biomarkers may be necessary to identify robust and reliable predictors of treatment response.