Changes in the Ki‐67 labeling index between primary breast cancer and metachronous metastatic axillary lymph node: A retrospective observational study

Abstract

Background The Ki‐67 labeling index (LI) is a well‐known prognostic factor for primary breast cancer, but its clinical significance for metachronous axillary lymph node (ALN) recurrence has not been well documented. Methods Ki‐67 expression in primary tumors (PTs) and ALN metastases (ALNMs) was evaluated in 21 patients and quantified to investigate the relationship between Ki‐67 LIs in PTs and metachronous ALNMs. Results The median Ki‐67 LIs in the PTs and ALNMs were 25.2% (range: 2.3–80.2%) and 70% (range: 10.4–97.4%), respectively. A majority of patients had higher Ki‐67 LIs in ALNMs than in PTs (76.2%, 16/21). Disease‐specific survival was significantly better in patients with a lower‐than‐median ALNM Ki‐67 LI (P = 0.019, log‐rank test). Receiver operating characteristic curves showed a PT Ki‐67 LI of 62.8% as the optimal cutoff value and an ALNM Ki‐67 LI of 65.1%. Accordingly, we divided the patients into four groups: PT Ki‐67 LI lower than 62.8%/ALNM Ki‐67 LI lower than 65.1%, PT Ki‐67 LI lower/ALNM Ki‐67 LI higher, PT Ki‐67 LI higher/ALNM Ki‐67 LI higher, and PT Ki‐67 LI higher/ALNM Ki‐67 LI lower. Disease‐specific survival was significantly better in patients with Ki‐67 LI lower/ALNM Ki‐67 LI lower than in the other groups. Conclusion This is the first study to show that the Ki‐67 LI in metachronous ALNM is a prognostic factor for patients with metachronous ALN recurrence of breast cancer.

Keywords

• Axillary lymph node
• Ki‐67 labeling index
• metachronous
• metastasis
• primary breast cancer