Residual cancer burden following neoadjuvant chemotherapy in breast cancer: A retrospective analysis by receptor subtype

ABSTRACT Background: Neoadjuvant chemotherapy (NACT) plays a key role in treating locally advanced breast cancer. While pathological complete response (pCR) is a strong prognostic indicator, residual cancer burden (RCB) offers a more comprehensive assessment by quantifying residual disease. Objectives: The primary objective was to evaluate pathological response to NACT using the distribution of RCB and pCR across breast cancer receptor subtypes. The secondary objective was to examine the association between receptor subtype and the likelihood of achieving pCR or low RCB scores. Materials and Methods: This retrospective study analyzed 129 female patients with breast cancer treated with NACT and surgery between March 2024 and February 2025. Tumors were classified into four receptor subtypes: HR+/HER2-, HR+/HER2+, HR-/HER2+, and triple-negative breast cancer (TNBC). Clinicopathological variables were analyzed by receptor subtype and RCB class (RCB 0–III). Results: Overall pCR (RCB-0) was achieved in 45.8% (n = 59) of patients. The highest pCR rates were observed in HR-/HER2+ tumors (65.4%, n = 17) and TNBC (58.1%, n = 25). HR+/HER2- tumors demonstrated the lowest pCR rate (16.1%, n = 5) and the highest proportion of RCB-III (54.8%, n = 17), while HR+/HER2+ tumors showed an intermediate response. RCB distribution differed significantly across receptor subtypes (χ 2 : 37.74, P < 0.001). Conclusion: Breast cancer subtypes differ significantly in response to NACT. HR-/HER2+ and TNBC exhibit favorable responses, whereas HR+/HER2- subtypes are more resistant. Incorporation of RCB scoring into routine pathology reporting may enhance post-neoadjuvant risk stratification and guide personalized care.