Expression of insulin-like growth factor I (IGF-I) in female breast cancer as related to established prognostic factors and long-term prognosis.

Abstract

The expression of insulin-like growth factor I (IGF-I) was analysed immunohistochemically in a series of 211 breast cancers with special emphasis on its relationship to conventional prognostic factors and long-term prognosis. Altogether, IGF-I was expressed by the tumour cells in 91% of the breast carcinomas, and by stromal cells in 29%. The expression of IGF-I in cancer cells was weakly related to a high proportion of intraductal growth (P = 0.032), distinct tumour margins (P = 0.048) and high S-phase fraction (P = 0.074). In a univariate analysis, IGF-I expression in cancer cells was significantly related to a high survival probability in the entire cohort (P = 0.0144) as well as in the axillary lymph node positive tumours (P = 0.0286). Alternatively, expression of IGF-I in the stromal cells was related to metastasis at the time of diagnosis (P = 0.05), tumour diameter (P = 0.04), DNA ploidy (P = 0.07) and nuclear pleomorphism (P = 0.025), but it was without prognostic significance in a univariate analysis (P > 0.1). In a multivariate analysis, the conventional prognostic factors were superior to IGF-I expression in predicting the disease outcome, albeit expression of IGF-I in tumour stroma showed some independent prognostic significance in axillary lymph node negative tumours. The results suggest that IGF-I expression is related to malignant histopathological features in breast cancer, and expression of IGF-I has independent prognostic significance in the early phases of the disease.