From the Guidelines
A Ki-67 proliferation index of 22% indicates a moderately to highly aggressive tumor behavior, suggesting that 22% of the tumor cells are actively dividing or proliferating. This is a measure of how quickly the cancer cells are growing and multiplying. Ki-67 is a protein found in cells during active phases of the cell cycle but not when cells are resting. Pathologists use special staining techniques to identify and count cells expressing this protein in tissue samples. A higher percentage indicates more aggressive tumor behavior, as more cells are actively dividing. For context, different types of cancers have different thresholds for what's considered high proliferation - in neuroendocrine tumors, for example, values above 20% are often considered high and may influence treatment decisions, as seen in the guidelines provided by the European Neuroendocrine Tumor Society 1.
Interpretation of Ki-67 Index
The Ki-67 index is used to evaluate the proliferation capacity of tumor cells, which can help determine the aggressiveness of the tumor. According to the European Neuroendocrine Tumor Society, a Ki-67 index of 22% would fall into the category of a well-differentiated, intermediate-grade tumor (G2), which usually has a mitotic count of 2 to 20/10 high-power field (HPF) and a Ki-67 index of 3% to 20% 1. However, since the Ki-67 index of 22% exceeds 20%, it may be considered as a high-grade tumor in some classifications.
Clinical Implications
This index helps oncologists determine how aggressive a cancer might be and can guide treatment choices, including whether more intensive therapy might be needed. The treatment approach may vary depending on the type of cancer, stage, and other pathological features. For neuroendocrine tumors, treatment options may include somatostatin analogs (SSAs), peptide-receptor radionuclide therapy (PRRT), chemotherapy, or a combination of these therapies, as suggested by various guidelines 1.
Importance of Contextual Interpretation
The Ki-67 score should always be interpreted by your doctor in the context of your specific cancer type, other pathological features, and overall clinical situation. This ensures that the treatment plan is tailored to the individual's needs, taking into account the aggressiveness of the tumor, potential symptoms, and the patient's overall health.
From the Research
Proliferation Index Ki67 22% Meaning
- The Ki67 proliferation index is a measure of cell proliferation, with higher values indicating increased cell growth and division 2, 3, 4.
- A Ki67 index of 22% means that 22% of the cells in the tumor are actively dividing, which can be an indicator of tumor aggressiveness and prognosis 2, 5.
- Studies have shown that a Ki67 index above 22% is associated with poorer survival rates in certain types of cancer, such as glioblastoma and breast cancer 2, 5.
- In contrast, a Ki67 index below 22% may indicate a less aggressive tumor with a better prognosis 2, 5.
- The Ki67 index can be used as a prognostic marker to guide treatment decisions, with higher indices potentially indicating a greater need for aggressive therapy 3, 4, 6.
Ki67 Index and Cancer Prognosis
- The Ki67 index has been shown to be a significant predictor of overall survival in patients with various types of cancer, including glioblastoma, breast cancer, and neuroendocrine tumors 2, 5, 6.
- A high Ki67 index is often associated with more aggressive tumor behavior, including increased metastasis and poorer response to treatment 3, 4, 6.
- The Ki67 index can be used in combination with other prognostic markers to provide a more accurate assessment of cancer prognosis and guide treatment decisions 5, 6.
Ki67 Index and Treatment Response
- The Ki67 index may be used to predict response to chemotherapy, with higher indices potentially indicating a greater likelihood of response 6.
- However, the relationship between Ki67 index and treatment response is complex, and other factors such as tumor type and grade should also be considered when making treatment decisions 6.