The association between Ki-67 expression and survival in breast cancer subtypes: a cross-sectional study of Ki-67 cut-point in northern Thailand.

Abstract

Background: Breast cancer is a major health concern worldwide, and Ki-67 level index is a prognostic factor that indicates tumor proliferation and predicts survival outcomes. However, the standard Ki 67 cut-off level varies between local laboratories, and in Thailand, there is no established optimal cut-off level.

Objective: This study aimed to determine the optimal cut-off point for Ki-67 expression and investigate the association between Ki-67 levels and other prognostic factors with 8-year overall survival.

Method: A retrospective review of Ki-67 levels was conducted in non-metastatic breast cancer patients treated at Maharaj Nakorn Chiangmai hospital from January 2013-December 2015, including 507 breast cancer patients.

Results: The ROC curve analysis identified the optimal Ki-67 cut-point as ≥ 30%, with 75% sensitivity and 48.85% specificity. Age over 60 was associated with higher mortality regardless of cancer stage. Locally advanced staging, nodal involvement, Ki-67 ≥ 30%, and triple-negative subtype correlated with poorer survival. Even after adjustments, these factors remained significant in prognostic evaluation. Chemotherapy notably improved survival, especially in high Ki-67 (≥ 30) patients. However, this effect was not seen in low Ki-67 patients. High Ki-67 patients receiving chemotherapy showed improved survival in early-stage, node-negative cases compared to those who did not receive chemotherapy. HER2-positive patients with high Ki-67 benefited from chemotherapy, but statistical significance was not reached in hormone-positive patients.

Conclusion: This study identified the optimal cut point for Ki-67 in Northern Thailand as 30%. Patients with KI-67 above 30% show significantly lower 8-year survival rates. This is especially relevant for low-risk patients, like those with hormonal subtypes or early-stage nodal negativity. In these cases, KI-67 becomes crucial for treatment decisions. Our study not only aids Northern Thailand's understanding but also aligns with broader research, emphasizing KI-67's vital role in planning treatment for low-risk breast cancer patients.