Cyclin B is an immunohistochemical proliferation marker which can predict for breast cancer death in low-risk node negative breast cancer

Patients with low-risk node negative breast cancer have an excellent prognosis with 5% breast cancer mortality at 10 years. However, prognostic factors are needed to identify poor prognostic patients who might benefit from adjuvant systemic therapy. Proliferation has been identified as the most important component of gene expression profiles. Cyclin B is a proliferative marker easily assessed by immunohistochemistry. We wanted to examine cyclin B as a prognostic factor in low-risk breast cancer patients. Patients and methods. Using an experimental study design, we compared women dying early from their breast cancer (n=17) with women free from relapse more than eight years after initial diagnosis (n=24). All women had stage I, node negative and hormone receptor positive disease. None had received adjuvant chemotherapy. Tumor samples were immunostained for cyclin B using commercial antibodies. Results. The mean percentage of cyclin B (12%) was significantly higher (p=0.001) in women dying from their breast cancer compared with women free from relapse ( 5%). High cyclin B (>= 9%) identified 11/17 patients dying from breast cancer and low cyclin B identified 22/24 patients free from relapse. The sensitivity and specificity of cyclin B was 65% and 92%, respectively. Discussion. We found that low-risk node negative patients with high expression of cylin B had a significantly worse outcome than patients with low expression of cyclin B. Cyclin B could separate patients with poor survival from those with good survival with 80% accuracy. We suggest that cyclin B might be a potent prognostic factor in this low-risk patient group.