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 (i.e., 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.