ER-positive tumours frequently co-express B-cell lymphoma 2 protein (BCL2). BCL2 is an anti-apoptotic protein shown to be a favourable prognostic marker and an index combining Ki67 and BCL2 was shown to be an independent predictor of survival.
A Ki67/BCL2 index would be relatively easy to implement. The aim of this study is to determine whether the Ki67/Bcl2 index can be validated in a local context.
Subjects diagnosed with invasive breast cancer from 2000 to 2003 were identified through the cancer registry. Ethics approval was obtained from Melbourne Health HREC and ratified by Walter and Eliza Hall Institute HREC. Archival blocks of the primary tumours were collated, sectioned and immunostained for BCL2 and Ki67 and scored using previously established protocols. The original pathology report determined size, grade, cancer type, ER, PgR, HER2 and nodal status. The subject’s medical record identified treatment modalities and survival. The Ki67/BCL2 index was correlated with outcome.
The complete pathological, clinical and outcome data were available for 186 women of 238 diagnosed with invasive breast cancer between 2000 and 2003. Preliminary analysis revealed that 124 (66%) were ER-positive (>1% ER positive tumour cells) and 167 (89%) were BCL2-positive (>10% BCL2 positive tumour cells). Tumours were positive for both BCL2 and ER in 122 cases (65%). Across the cohort, 163 (87%) subjects were alive five years after diagnosis. Univariate and multivariate analysis of the biomarkers and index is currently being carried out and will be reported.
The Ki67/BCL2 index could help shape decision making for women with breast cancer if further work confirms that it is a prognostic marker. Since BCL2 is being investigated as a therapeutic target for women with metastatic breast cancer (mBEP, ACTRN12615000702516), identification of BCL2 positive tumours could also serve as a predictive biomarker.