Background: Decisions in breast cancer as to treatment options supplementing surgery are based on classic prognostic factors. However, these factors are of little help when deciding against adjuvant chemo-/hormonotherapy. Therefore, there is a need to search for additional factors which modify the prognosis in breast cancer patients. The aim of this study was to determine associations of the proliferation index (PI) with some clinical and anatomical factors, as well as with the overall survival (OS) and distant metastasis-free survival (DMS) rates in invasive ductal breast cancer. The study also attempted to identify independent prognostic factors.
Material and methods: PI was calculated following immunohistochemistry with a monoclonal antibody against Ki-67 (MIB-1) protein in 767 invasive ductal breast cancer patients seen at the West Pomeranian Oncology Center between 1990 and 2001. The mean follow-up time in the group of surviving patients was 72.7 months. The cut-off value of 10% for high/low PI was adopted.
Results: The mean value of PI was 15.15% (median 11.2%). High PI correlated with young age of patient, tumor diameter, high histological malignancy score, absence of estrogen receptor in cells, and metastases to axillary lymph nodes. The frequency of distant metastases and high mortality risk correlated with high PI in the whole group and in subgroups without or with metastases to 1-3 axillary lymph nodes, with grade II cancers according to the B-R score, and with the presence of estrogen receptors in the tumor. PI proved to be an independent prognostic factor in the whole group and in the subgroup of patients with axillary node metastases. PI was the sole independent prognostic factor in patients with metastases to 1-3 axillary lymph nodes.
Conclusions: PI is an independent prognostic factor in patients with invasive ductal breast carcinoma. PI can be used to identify patients with a worse prognosis among patients with metastases to 1-3 axillary lymph nodes or with grade II cancer according to the Bloom-Richardson score. PI strongly correlates with other pathological and clinical parameters. In combination with other prognostic factors, PI can be used for prediction of metastases to axillary lymph nodes.