Prognostic and recurrence risk predictive values of tumor infiltrating lymphocytes in HER2-low breast cancer.

Background: With the emergence of novel anti-HER2 antibody drug conjugates, patients with HER2-low breast cancer have received increased attention. Tumor-infiltrating lymphocytes (TILs) are significantly associated with survival benefits in cancers. However, their prognostic value in patients with low her2 breast cancer is unknown. Therefore, we aimed to determine the relationship between TILs and recurrence in patients with HER2-low breast cancer.

Methods: Clinicopathological data were retrospectively collected from patients with human epidermal growth factor receptor 2 (HER2) low-expression breast cancer who underwent consultations at Qingdao University Affiliated Hospital. We determined the correlation between TILs and disease-free survival (DFS) followed by the threshold value of TILs using X-tile software. Survival was assessed using Kaplan-Meier analysis, and cox regression analysis was performed for recurrence risk modeling.

Results: Our study showed a 15% TIL level was the optimal cutoff for DFS. The low and high TILs survival curves showed significant differences in the log-rank test (p = 0.009). Cox regression analyses found that lymph node stage, histologic grading, TILs, and Ki-67 were independent variables influencing the prognosis (p < 0.05). On this basis, we developed a risk prediction model to accurately predict the 3- and 5-year disease-free survival rates of patients with HER2-low breast cancer, the model demonstrated good overall performance.

Conclusion: TILs are associated with recurrence in patients with breast cancer and low HER2 levels. TILs > 0.15 is a reliable indicator of DFS. For patients with low TILs (≤ 0.15), extensive follow-up is required. These findings provide a basis for targeted, individualized treatment.