Ki-67 labeling index is a predictive marker for a pathological complete response to neoadjuvant chemotherapy in breast cancer

BACKGROUND A pathological complete response (pCR) after neoadjuvant chemotherapy (NCT) is a strong indicator of the benefit of therapy and presents an early surrogate for a favorable long-term outcome. It remains unclear whether Ki-67, a marker for tumor proliferation, can function as a predictor of the response to NCT in breast cancer. The objective of this meta-analysis was to compare the pCR rate and clinical outcomes in breast cancer patients with different Ki-67 labeling indexes (Ki-67 LI) who received NCT. METHODS Clinical studies were retrieved from the electronic databases of PubMed, Embase, Clinical Trials, Wanfang, and the Chinese National Knowledge Infrastructure, from their inception to July 31, 2017. Meta-analysis was performed on pool eligible studies to determine whether Ki-67 LI was associated with the pCR rate and clinical outcomes of breast cancer patients who were treated with NCT. Pooled analyses were performed using fixed effects models. Two reviewers screened all titles and abstracts and independently assessed all articles. RESULTS A total of 36 studies involving 6793 patients were included in the meta-analysis. Pooled analysis results revealed that patients with high Ki-67 LI exhibited significantly higher pCR rates (odds ratio [OR] = 3.94, 95% confidence interval [CI]: 3.33-4.67, P <.001) but poorer relapse-free survival (OR = 1.99, 95% CI: 1.39-2.85, P <.001) than those with low Ki-67 LI, but there was no significant difference in objective tumor response rate. CONCLUSION The meta-analysis reported here demonstrates that pretherapeutic Ki-67 LI is associated with pCR in breast cancer patients undergoing NCT. More phase III randomized clinical trials will be required to confirm our findings.