Immunologic proliferation marker Ki-S2 as prognostic indicator for lymph node-negative breast cancer

Area of Science:

• Oncology
• Immunohistochemistry
• Cancer Prognostics

Background:

• Accurate prognosis is crucial for effective treatment of lymph node-negative breast cancer.
• Existing prognostic models require improvement for better patient stratification.
• The study investigates the utility of Ki-S2, an immunohistochemical marker for proliferating cells, in breast cancer prognosis.

Purpose of the Study:

• To evaluate the accuracy of the Ki-S2 labeling index as a prognostic indicator in lymph node-negative breast cancer.
• To determine if Ki-S2 can improve existing prognostic models.
• To identify patients with a low risk of recurrence who may benefit from reduced adjuvant therapy.

Main Methods:

• A cohort of 371 Swedish women with lymph node-negative breast cancer was studied with a median follow-up of 95 months.
• Tumor cell proliferation was assessed using immunohistochemistry with Ki-S2 and Ki-S5 antibodies.
• S-phase fraction was measured by flow cytometry, and a combined prognostic index was calculated.

Main Results:

• The Ki-S2 labeling index was the most significant predictor of overall, disease-specific, and disease-free survival in multivariate analyses (P<.0001).
• Patients with a Ki-S2 labeling index of ≤10% had a life expectancy similar to age-matched controls without breast cancer.
• A high Ki-S2 labeling index was associated with up to a 20-fold increased risk of mortality.

Conclusions:

• Cellular proliferation, as indicated by the Ki-S2 labeling index, is a key determinant of breast cancer behavior.
• The Ki-S2 labeling index provides an accurate prognosis by reflecting the percentage of cells in the S through M phases of the cell cycle.
• Measuring the Ki-S2 labeling index can enhance clinical prognosis and identify low-risk patients who may not require adjuvant therapy.