Increased serum insulin associated with increased risk of prostate cancer recurrence

BACKGROUND. In the present study, we assessed the relationship of serum insulin levels and risk of recurrence in men with localized prostate cancer because of the relationship of insulin to the development of prostate cancer, and because insulin is a growth factor. METHODS. Participants in our study were found through urology and radiation oncology clinics, and all eligible patients were asked to take part. All patients were asymptomatic and had been initially diagnosed on the basis of rising PSA or abnormal physical examination. Histological confirmation of diagnosis was obtained for all subjects. Serum insulin levels were determined by chemoluminescent assay with a standard, commercially available instrument (Immulite Diagnostic Products Corporation, Los Angeles, CA). Patients were divided into three risk groups: Low risk: serum PSA less than or equal to 10, stage less than or equal to T2a, or Gleason grade less than or equal to 6; Medium risk: serum PSA 10-15, Gleason 7 or stage less than or equal to T2b; High risk: Gleason > 7, tumor in seminal vesicle biopsy, serum PSA > 15 or stage T2c or T3. RESULTS. Men, 112 in number, with prostate cancer were studied. There was a significant increase in serum insulin with risk group (P = 0.002, one-way ANOVA). Tukey's multiple range test showed that the insulin levels of high risk patients were significantly higher than the insulin levels of medium and low risk patients (P = 0.05) but the insulin levels of medium and low risk patients were not significantly different from one another. CONCLUSIONS. Urologists are actively seeking additional biomarkers of prostate cancer aggressiveness. Many prostate cancers are quite indolent and may never cause a problem, but it is now impossible to identify such tumors with certainty. Further studies of serum insulin levels in prostate cancer as a biomarker might, therefore, be worthwhile. With more and better biomarkers, many older men might be spared the rigors of radiation therapy and/or surgery, and their complications. Also, new prostate cancer therapies might be directed toward inhibiting the mitogenic effects of insulin. (C) 2002 Wiley-Liss, Inc.