Insulin-like growth factor 1 (IGF-l), IGF-1 density, and IGF-1/PSA ratio for prostate cancer detection

Objectives. Recent studies suggest an association between increased serum levels of insulin-like growth factor 1 (IGF-1) and an increased risk of prostate cancer (PCa). We prospectively analyzed the value of IGF-1, IGF-density (IGFD), and IGF-1/prostate-specific antigen (PSA) ratio for early detection of prostate cancer. Methods. IGF-1, IGFD, and IGF-1/PSA ratio were determined prospectively during an 11-month period in the serum from 245 consecutive white men with PSA levels between 2.5 and 15 ng/mL. Octant biopsy (including transition zone biopsy) was performed. A second biopsy was performed 6 weeks later if the first biopsy was negative. Prostate volume was measured using transrectal ultrasound and the prolate ellipsoid method. Receiver operating characteristic curves were performed to compare tests. Results. No evidence of malignancy was found in 174 patients (71%), and PCa was found in 71 (29%). The mean age for patients with no evidence of malignancy and those with PCa was 67.7 +/- 9 and 65.7 +/- 6 years, respectively (P = 0.17). IGF-1, IGFD, IGF-1/PSA ratio, and PSA were significantly higher in patients with PCa than in those with benign disease (P = 0.03, P = 0.045, P = 0.001,and P = 0.018, respectively). The area under the curve Value derived from the receiver operating characteristic curves for IGF-1/PSA ratio, PSA, IGFD, and IGF-1 was 71%, 61%, 60%, and 58%, respectively. At 95% sensitivity, the specificity of the IGF-1/PSA ratio was significantly greater than that of all other parameters (P<0.0001). An IGF-1/PSA cutoff value of 25 afforded a 95% sensitivity for detecting PCa and would have avoided unnecessary biopsies in 24.1% of patients. Conclusions. Although IGF-1 and IGFD were unable to enhance the performance of PSA in our study, the IGF-1/PSA ratio significantly improved PCa detection over the use of PSA alone. Thus, increased IGF-1 levels (ie, the IGF-1/PSA ratio) may not only be associated with an increased PCa risk but may also be a useful tool for early detection. UROLOGY 54: 603-606, 1999. (C) 1999, Elsevier Science Inc.