Correlation Between Platelet Indices and Residual Cancer Burden Score in Patients with Locally Advanced Luminal B HER2-Negative Breast Cancer Receiving Neoadjuvant Chemotherapy

<title>Abstract</title> <p>Background Luminal B HER2-negative breast cancer often shows an incomplete pathological response after neoadjuvant chemotherapy. Residual Cancer Burden (RCB) is a standardized histopathological tool used to quantify post-treatment residual disease and has prognostic value after neoadjuvant therapy. Platelets interact with tumor cells through inflammatory, angiogenic, and metastatic pathways, and these interactions may be reflected by platelet indices, including mean platelet volume (MPV), platelet distribution width (PDW), and plateletcrit (PCT). The relationship between platelet indices and RCB in locally advanced Luminal B HER2-negative breast cancer has not been specifically evaluated in Indonesia. Methods This was an observational analytic study with a cross-sectional design using secondary data from patients with locally advanced Luminal B HER2-negative breast cancer who received neoadjuvant chemotherapy at Dr. Hasan Sadikin General Hospital, Bandung, during 2021–2025. Eligible patients were adult women who had completed neoadjuvant chemotherapy and subsequent mastectomy, with available pre-treatment platelet index data and sufficient pathology information to calculate RCB. A total of 106 patients were included. Bivariate and comparative analyses were performed to assess the correlation between MPV, PDW, PCT, and RCB score. Results Bivariate analysis in 106 patients showed weak correlations between platelet indices and RCB score, with correlation coefficients of -0.050 for MPV (p = 0.420), -0.079 for PDW (p = 0.420), and 0.079 for PCT (p = 0.421). Categorical analysis also showed no significant association between MPV, PDW, or PCT categories and RCB group (all p &gt; 0.05). Comparative analysis across RCB groups similarly demonstrated no significant differences in MPV, PDW, or PCT. Conclusions Pre-treatment platelet indices were not significantly correlated with RCB score in patients with locally advanced Luminal B HER2-negative breast cancer receiving neoadjuvant chemotherapy. These findings suggest that MPV, PDW, and PCT are not reliable standalone biomarkers for estimating residual tumor burden in this setting. Further studies incorporating other hematologic and inflammatory parameters are warranted.</p>