The Systemic Immune-Inflammation Index is a Predictor of Chemotherapy Sensitivity and Disease-Free Survival in Patients With Hormone Receptor-Positive Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer.

Abstract

Background: The relationship between the systemic immune-inflammation index (SII), chemotherapy sensitivity, and prognosis in HR+HER2- breast cancer (BC) has not been extensively studied.

Patients and methods: Clinical data from 980 patients diagnosed with HR+HER2- BC between June 2012 and June 2016 were collected. Patients were divided into low- and high-SII groups according to median SII value. Differences among variables were assessed using the chi-squared test. The inverse probability of treatment weighting (IPTW) method was used to control bias. The associations between clinicopathological factors, baseline SII, and disease-free survival (DFS) were analyzed using Kaplan-Meier curves and Cox analyses.

Results: The median follow-up period was 37 months (5-77). 480 patients underwent neoadjuvant chemotherapy, and low baseline SII values were associated with higher pathological complete response (pCR) rates than those in the high SII group (16.4% vs. 9.2%; P = .019). Multivariate analyses revealed that larger tumor size, more lymph node involvement, high Ki-67 score, and high baseline SII were independent prognostic factors for worse outcomes in patients with HR+HER2- BC. The risk for metastasis/recurrence was higher in the high SII group compared with that in the low SII group (hazard ratio 2.07 [95% CI, 1.35-3.19]; P = .001). After IPTW, a similar result was obtained, in that a high SII value was significantly associated with worse DFS among patients with HR+HER2- BC.

Conclusion: A low baseline SII was associated with higher pCR rates after neoadjuvant chemotherapy and was an independent prognostic factor for better DFS outcomes in patients with HR+HER2- BC.