Prognostic impact of discrepant Ki67 and mitotic index on hormone receptor-positive, HER2-negative breast carcinoma

• Published in: British journal of cancer Vol. 113; no. 7; pp. 996 - 1002
• Main Authors: Rossi, L, Laas, E, Mallon, P, Vincent-Salomon, A, Guinebretiere, J-M, Lerebours, F, Rouzier, R, Pierga, J-Y, Reyal, F
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29.09.2015; Nature Publishing Group
• Subjects: 692/699/67/1347; 692/699/67/1857; 692/700/1750; Biomedical and Life Sciences; Biomedicine; Breast Neoplasms - metabolism; Breast Neoplasms - mortality; Breast Neoplasms - pathology; Cancer Research; Clinical Study; Drug Resistance; Epidemiology; Female; Humans; Ki-67 Antigen - analysis; Mitotic Index; Molecular Medicine; Oncology; Prognosis; Receptor, ErbB-2 - metabolism; Receptors, Steroid - metabolism; Survival Analysis; treatment; breast cancer; proliferation; Ki67; mitotic index; prognosis
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/bjc.2015.239

Background: Inconsistencies between mitotic index (MI) and Ki67 measures have been identified in many breast tumour samples. The aim of this study was to describe the prognosis of hormone receptor-positive (HR+) HER2− tumours having discrepant MI and Ki67. Methods: We included a cohort of breast cancer patients initially treated by surgery between 2001 and 2005 in the Institut Curie. Breast cancer-specific survival (BCSS) and disease-free survival (DFS) were analysed according to three proliferation groups: high MI/high Ki67 (MI=3, Ki67>20%), low MI/low Ki67 (MI<3, Ki67⩽20%) and discrepant (high MI/low Ki67 or low MI/high Ki67). Results: Among the 1430 patients, 19.6% had discrepant Ki67 and MI, 11.6% had high markers and 68.8% had low markers. The 5-year BCSS was 95.8%, 95% CI (0.93–0.98) in the discrepant group, 99.3%, 95% CI (0.993–0.999) in the low-proliferation group and 91.8%, 95% CI (0.88–0.96) in the high-proliferation group. In multivariate analysis, the survival of the discrepant group was lower than that of the low-proliferation group: BCSS hazard ratio (HR)=3.01 (1.32–6.84; P =0.008) and DFS HR=2.07, 95% CI (1.31–3.26; P =0.002). Among grade 2 tumours in multivariate analysis, DFS of the discrepant group was lower than that of the low MI/low Ki67 group: HR=1.98, 95% CI (1.14–3.46), P =0.02. Regarding BCSS, the obtained results were similar. Conclusion: The prognosis of patients with discrepant MI and Ki67 appears intermediate between that of low MI/low Ki67 and high MI/high Ki67 groups. These markers should be jointly analysed to clarify prognosis.