Breast Cancer. 2026 Jun 12. doi: 10.1007/s12282-026-01869-w. Online ahead of print.
ABSTRACT
BACKGROUND: Bevacizumab is an anti-angiogenic agent that inhibits tumor vascularization and thereby suppresses tumor growth. Tumor-infiltrating lymphocytes (TILs), particularly CD8-positive TILs, play a critical role in the antitumor immune response. However, little is known about the effect of bevacizumab-containing chemotherapy on CD8-positive TIL dynamics. This study aimed to evaluate changes in CD8-positive TILs before and after treatment in patients with advanced breast cancer receiving bevacizumab in combination with chemotherapy.
METHODS: Thirty patients with initially inoperable advanced breast cancer who responded to first-line bevacizumab-containing chemotherapy and subsequently became eligible for surgery were included. CD8-positive TILs were assessed by immunohistochemistry in biopsy samples obtained before treatment and in surgical specimens collected after treatment. Stromal CD8-positive TILs were classified as low, intermediate, or high, based on their proportion among total stromal TILs.
RESULTS: Of the 30 patients, 20 had luminal-like breast cancer and 10 had triple-negative breast cancer. Before treatment, CD8-positive TIL expression was low in 16 patients (64.0%), intermediate in 6 (24.0%), and high in 3 (12.0%). After treatment, 10 patients (33.3%) showed low expression, 11 (36.7%) had intermediate expression, and 9 (30.0%) had high expression, indicating an increase in CD8-positive TIL levels. The high pathological response (a pathological response grade of 2 or higher) rate was 36.7%, and patients with increased CD8-positive TILs tended to show higher pathological response and better overall survival, although these differences did not reach statistical significance. In contrast, the ypT stage was significantly lower in cases with high post-treatment CD8-positive TIL expression, suggesting that immune activation after bevacizumab may contribute to local tumor regression.
CONCLUSIONS: Bevacizumab-containing chemotherapy appears to enhance CD8-positive TIL infiltration in primary breast tumors, which may contribute to improved local tumor regression and better therapeutic outcomes.
PMID:42286385 | DOI:10.1007/s12282-026-01869-w
