{"entity":{"id":"ki-67-index","kind":"biomarker","name":"Ki-67 index (proliferation by IHC)","aka":["Ki-67","Ki67","Ki-67 index","Ki-67 labelling index","Ki-67 score","MIB-1 index","Ki-67 >= 20%","Ki-67 ≥20%","proliferation index"],"tldr":"Ki-67 is the percentage of tumour cells that are dividing. In neuroendocrine tumours it sets the grade; in breast cancer a 20 percent cut-off was briefly a condition of adjuvant abemaciclib, then dropped from the label in 2023.","summary":"The Ki-67 labelling index is the percentage of tumour cell nuclei staining with the MIB-1 antibody. In gastroenteropancreatic neuroendocrine tumours the WHO classification grades G1 (< 3 percent), G2 (3 to 20 percent) and G3 (> 20 percent). In breast cancer the October 2021 FDA approval of adjuvant abemaciclib (monarchE cohort 1) required node-positive, high-risk, HR-positive HER2-negative disease with Ki-67 >= 20 percent by the Ki-67 IHC MIB-1 pharmDx (Dako Omnis) companion diagnostic; the March 2023 label expansion removed the Ki-67 requirement, and the current label describes the assay only in the trial narrative. The International Ki-67 in Breast Cancer Working Group considers scores of 5 percent or less and 30 percent or more reproducible and the range between them not.","asOf":"2026-09-23","links":[{"label":"Verzenio prescribing information (DailyMed)","url":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=be4bc0de-0fdc-4d46-8d25-be43c79e6a06"}],"tags":["biomarker","proliferation"],"related":["er-status","pr-status"],"cancers":["breast-hr-positive","hr-positive-early-high-risk","neuroendocrine","pancreatic-net","lung-net"],"sections":[],"technologies":[],"targets":[],"drugs":["abemaciclib"],"companies":[],"institutions":[],"pathways":[],"terms":["net-grade-ki67","proliferation","ihc"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"target":"mki67","measurement":"ihc-score","scoringRule":{"text":"Percentage of tumour cell nuclei staining for Ki-67 (MIB-1), counted in the invasive tumour; in monarchE cohort 2 a score of 20 percent or more was required, measured centrally with the Ki-67 IHC MIB-1 pharmDx.","quote":"Breast tumor samples were tested at central sites using the Ki-67 IHC MIB-1 pharmDx (Dako Omnis) assay to establish if the Ki-67 score was ≥20%.","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=be4bc0de-0fdc-4d46-8d25-be43c79e6a06","sourceLabel":"Verzenio prescribing information (clinical studies section)"},"thresholds":[{"value":"Ki-67 >= 20% (2021 adjuvant approval, requirement removed March 2023)","drugId":"abemaciclib","cancerId":"hr-positive-early-high-risk","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=be4bc0de-0fdc-4d46-8d25-be43c79e6a06","quote":"To be enrolled in cohort 2, patients had to have 1-3 pALN and Ki-67 score ≥20%.","status":"historic","note":"The current label no longer restricts adjuvant abemaciclib by Ki-67; the threshold is kept as the historic 2021 approval condition."}],"definedBy":{"label":"WHO Classification of Tumours, Digestive System Tumours, 5th edition (neuroendocrine grading by Ki-67)","url":"https://tumourclassification.iarc.who.int/"},"tests":[],"assays":["ki67-mib1"],"companionDiagnostics":[],"forPatient":"Ki-67 tells you how fast the cancer is growing. In a neuroendocrine tumour it sets the grade, which steers treatment. In early breast cancer a high Ki-67 (20 percent or more) was once required for adjuvant abemaciclib; it no longer is, but the number still helps your team judge how much benefit chemotherapy or a CDK4/6 inhibitor is likely to add."},"route":"/biomarkers/ki-67-index/","neighbours":{"biomarker":[{"id":"er-status","kind":"biomarker","name":"ER status (oestrogen receptor by IHC)","route":"/biomarkers/er-status/"},{"id":"pr-status","kind":"biomarker","name":"PR status (progesterone receptor by IHC)","route":"/biomarkers/pr-status/"},{"id":"sstr-pet-expression","kind":"biomarker","name":"Somatostatin receptor expression by PET (SSTR-positive)","route":"/biomarkers/sstr-pet-expression/"}],"cancer":[{"id":"hr-positive-early-high-risk","kind":"cancer","name":"High-risk early HR-positive breast cancer","route":"/cancers/hr-positive-early-high-risk/"},{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"},{"id":"lung-net","kind":"cancer","name":"Lung neuroendocrine tumours (typical and atypical carcinoid)","route":"/cancers/lung-net/"},{"id":"neuroendocrine","kind":"cancer","name":"Neuroendocrine tumours","route":"/cancers/neuroendocrine/"},{"id":"pancreatic-net","kind":"cancer","name":"Pancreatic neuroendocrine tumours","route":"/cancers/pancreatic-net/"}],"drug":[{"id":"abemaciclib","kind":"drug","name":"Abemaciclib","route":"/drugs/abemaciclib/"}],"term":[{"id":"ihc","kind":"term","name":"Immunohistochemistry (IHC)","route":"/terms/ihc/"},{"id":"net-grade-ki67","kind":"term","name":"Neuroendocrine tumour grade (Ki-67) and WHO classification","route":"/terms/net-grade-ki67/"},{"id":"proliferation","kind":"term","name":"Proliferation","route":"/terms/proliferation/"}],"target":[{"id":"mki67","kind":"target","name":"Ki-67 (MKI67)","route":"/targets/mki67/"}]}}