Correlation of the Ki67 Working Group prognostic risk categories with the Oncotype DX Recurrence Score in early breast cancer

• Published in: Cancer 2022-10, Vol.128 (20), p.3602-3609
• Main Authors: Patel, Rima, Hovstadius, Malin, Kier, Melanie W., Moshier, Erin L., Zimmerman, Brittney S., Cascetta, Krystal, Jaffer, Shabnam, Sparano, Joseph A., Tiersten, Amy
• Format: Article
• Language: English
• Subjects: Agreements; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Breast cancer; breast neoplasms; Breast Neoplasms - pathology; Chemotherapy; Epidermal growth factor; estrogen receptor; Female; Gene Expression Profiling; genomics; Growth factors; Hormones; Humans; Immunohistochemistry; Ki-67 Antigen - genetics; Ki-67 Antigen - metabolism; Ki67 antigen; Lymph nodes; Neoplasm Recurrence, Local - pathology; Oncology; Progesterone; Prognosis; Receptors; Receptors, Progesterone - genetics; Receptors, Progesterone - metabolism; Retrospective Studies; tumor biomarkers; Tumors; Working groups
• ISSN: 0008-543X; 1097-0142; 1097-0142
• DOI: 10.1002/cncr.34426

Background The relationship between Ki67 assessed by immunohistochemistry (IHC) and the Oncotype DX Recurrence Score (RS) is unclear. The objective of this study was to determine the correlation between the 21‐gene RS and IHC‐measured Ki67 with the prognostic classification groups recommended by the International Ki67 Working Group (IKWG). Methods The authors performed a retrospective chart review of women who had hormone receptor (HR)–positive, human epidermal growth factor receptor 2–negative early breast cancer with zero to three positive lymph nodes and both Ki67 and the 21‐gene RS performed at their institution from 2013 to 2021. Patients were categorized into low (≤5%), intermediate (6%–29%), and high Ki67 groups (≥30%) according to IKWG recommendations. Overall agreement and risk‐stratified agreement between Ki67 and RS were assessed with the proportion of agreement and the κ statistic. Results The study included 525 patients with HR‐positive breast cancer. Among the 49% of patients with intermediate Ki67 values of 6%–29%, the distribution of low (0–10), intermediate (11–25), and high RS (26–100) was 19%, 66%, and 15%, respectively. There was slight agreement (κ = 0.01–0.20) between Ki67 and RS (κ = 0.027) in the overall population, although this was not significant (p = .1985). There was fair agreement (κ = 0.21–0.40) between high Ki67 and RS values (κ = 0.280; p  .0001) but not lower Ki67 values. A positive nodal status and a larger tumor size were associated with higher Ki67 values (p = .0059 and p