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 l evels of insulin-like growth factor 1 (IGF-1) and an increased risk of pros tate cancer (PCa). We prospectively analyzed the value of IGF-1, IGF-densit y (IGFD), and IGF-1/prostate-specific antigen (PSA) ratio for early detecti on of prostate cancer. Methods. IGF-1, IGFD, and IGF-1/PSA ratio were determined prospectively dur ing 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 f irst biopsy was negative. Prostate volume was measured using transrectal ul trasound and the prolate ellipsoid method. Receiver operating characteristi c 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 malig nancy 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 = 0.04 5, P = 0.001,and P = 0.018, respectively). The area under the curve Value d erived from the receiver operating characteristic curves for IGF-1/PSA rati o, PSA, IGFD, and IGF-1 was 71%, 61%, 60%, and 58%, respectively. At 95% se nsitivity, 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 unn ecessary 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 detect ion 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 al so be a useful tool for early detection. UROLOGY 54: 603-606, 1999. (C) 199 9, Elsevier Science Inc.