The prognostic value of oncogenic antigen 519 (OA-519) expression and proliferative activity detected by antibody MIB-I in node-negative breast cancer

The prognostic value of oncogenic antigen 519 (OA-519) expression and tumour proliferative activity was evaluated in a retrospective series of 118 patients with low-risk breast cancer. Low risk was defined as negative axillary nodes, tumour diameter ?50 mm, and no histological evidence of invasion of skin or deep fascia (=T₁N₀M₀ and T₂N₀M₀). The median follow-up time was 104 months (range 5–143 months). Immunohistochemical analysis of OA-519 expression was performed on formalin-fixed, paraffin-embedded tissue. The proliferative activity was estimated using a Ki-67 equivalent monoclonal antibody (MIB-1), which is applicable on formalin-fixed, paraffin-embedded tissue after microwave pretreatment. OA-519 was expressed in about one-third of the tumours and the percentage of proliferating cells (the MIB-1 index) ranged between 1 and 72 per cent (median 17 per cent). Using multivariate Cox analysis, both the MIB-1 index and OA-519 expression were of independent prognostic value (2p?0·01), and the combined immunohistological approach may therefore be useful in selecting patients with node-negative breast cancer who might benefit from adjuvant therapy.