Prostatic fluid-free insulin-like growth factor-1 in relation to prostate cancer

OBJECTIVES: To establish the feasibility of measuring free insulin-like growth factor-1 (IGF-1) in prostatic fluid and to determine if there is a difference in free IGF-1 levels in the prostatic fluid of patients with prostatic adenocarcinoma and in normal men. PATIENTS AND METHODS: Prostatic fluid samples were collected from men with histologically confirmed prostate cancer and from control subjects with no malignancy. Prostatic fluid and serum free IGF-1 levels were measured in duplicate by radioimmunoassay, and the differences analysed using the Mann-Whitney U-test and Pearson correlation. RESULTS: Prostatic fluid free IGF-1 concentrations did not differ significantly (P = 0.23) and there was no difference in serum free IGF-1 levels between the groups. While serum PSA level was significantly correlated with age (P < 0.001) the free IGF-1 level of prostatic fluid was not. There was also no correlation between prostatic fluid free IGF-1 and serum PSA levels. CONCLUSIONS: Free IGF-1 can be detected in prostatic fluid with acceptable sensitivity. However, the free IGF-1 level in prostatic fluid does not help to detect patients with prostate cancer and is not a tumour marker.