Investigation of the Residual Tumor Burden and Prognosis of Breast Cancer

Breast cancer remains a significant global health concern. The residual cancer burden (RCB) system quantifies response to neoadjuvant therapy. This study evaluates pathological response as a prognostic indicator in patients with residual invasive breast carcinoma through a retrospective single-center validation.

In this retrospective cohort study, we analyzed 100 surgical specimens from patients who underwent neoadjuvant therapy and mastectomy at a Brazilian public hospital. The RCB was calculated according to MD Anderson guidelines and classified as RCB-0 (complete response), RCB-I (minimal), RCB-II (moderate), or RCB-III (extensive). Clinicopathological correlations and survival analysis were performed.

The cohort was predominantly female (98%) with a mean age of 58.7 years. Invasive carcinoma of no special type was most common (86%). Extensive residual burden (RCB-III) predominated (66%), followed by RCB-II (29%), RCB-0 (3%), and RCB-I (2%). Higher RCB class was significantly associated with higher tumor grade (p< 0.0001), larger tumor size (p< 0.0001), greater lymph node involvement (p< 0.0001), and distant metastasis (p= 0.039). Mortality correlated with increasing RCB (74.6% of deaths were RCB-III). Survival analysis showed a significant difference among RCB classes (p= 0.024), with the most pronounced difference between RCB-II and RCB-III (p= 0.007). The luminal A subtype was more common in RCB-0, while luminal B HER2+ and triple-negative subtypes were more frequent in RCB-III.

Within this historical cohort, the RCB index provides valuable prognostic information, effectively stratifying institutional patients based on recurrence and metastasis risk. While its routine adoption in clinical practice is supported to complement risk stratification, conclusions regarding its universal independent value across all classes are bounded by the low number of RCB-0 and RCB-I cases.