Perioperative Changes in Peripheral Natural Killer Cell Activity and Their Association With Clinicopathological Features in Breast Cancer: A Single-Center Cohort Study.

OBJECTIVE: This study aimed to evaluate perioperative changes in peripheral blood natural killer (NK) cell activity (ACT) in patients with breast cancer and to investigate the relationship between NK activity and clinicopathological characteristics. METHODS: A single-center retrospective cohort including 34 female patients with available preoperative and postoperative NK activity measurements was analyzed. Clinical and pathological variables were obtained from medical records. NK activity levels at two time points were compared, and the association between NK activity difference and age, tumor size, TNM stage, hormone receptor status, HER2 expression, Ki-67 index, number of metastatic lymph nodes, and serum tumor markers was assessed. NK cell activity was assessed using the NK Vue assay (ATgen, Seongnam, Republic of Korea), a whole-blood stimulation assay based on interferon-gamma (IFN-γ) release. RESULTS: Postoperative NK activity significantly increased compared with preoperative levels (p = 0.041). However, the change in NK activity was not significantly associated with tumor stage, lymph node involvement, tumor size, proliferation index, receptor status, HER2 expression, metastatic lymph node count, or serum tumor markers (all p > 0.05). The overall metastatic rate during follow-up was low. CONCLUSION: Surgical treatment appears to exert a favorable effect on peripheral NK cell activity in breast cancer. The absence of a clear correlation between NK activity changes and clinicopathological parameters suggests that NK responses may reflect an individualized immunologic capacity rather than tumor-specific features. Larger prospective studies integrating NK cell subsets and functional phenotyping are required to better define the prognostic and predictive value of NK cell activity in breast cancer.