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Correspondence re: Chokkalingam A. et al., Insulin-like Growth Factors and Prostate Cancer

A Population-based Case-Control Study in China. Cancer Epidemiol. Biomark. Prev., 10: 421–427, 2001

Department of Social and Preventive Medicine [P. M., P. G.], and Department of Pediatrics, Center for Diabetes, [T. Q.], University at Buffalo, State University of New York, Buffalo, New York 14214

We read with great interest the article by Chokkalingam A. et al. (1) , on the association of IGF-I¹ and prostate cancer risk. Their analysis yielded evidence of a relevant association between serum levels of IGF-I and the probability of developing prostate cancer in a low-risk population in China. The study results were consistent with findings in high-risk Western populations (2, 3, 4) . The GH is the major transcriptional inducer of IGF-I gene expression in the liver and in several extraepatic tissues. IGF-I acts as an effector of GH action and also participates in the regulation of GH at both the pituitary and the hypothalamic levels (5) . In consequence of the relevant consistency of the association of IGF-I and prostate cancer and the established role of the GH as IGF-I-regulating factor, we planned to determine serum GH levels in stored serum from prostate cancer cases and control subjects collected in a previously conducted case-control study in the greater Buffalo area (Erie County, NY). As a first step, we evaluated the reliability of the GH serum measurement in 51 healthy men randomly selected among participants recruited as control subjects in the case-control study. After the first blood collection, the 51 men were asked to come to our recruitment center for a second blood drawing. Both of the blood collections were performed between 7:30 and 9:00 a.m. The second blood drawing was performed 1 year after the first one, in the same month, on the same day of the month, and at the same hour and minute. Exclusion criteria were as follows: hormonal treatment, prostate cancer or major chronic diseases (i.e., cancer, cardiovascular disease, diabetes) diagnosed at the time of recruitment and in the time interval between the two blood collections. All of the 51 study subjects could participate in both of the blood collections. To reduce the technical variability effect on the study results, samples for each participant were retrieved and assayed in the same run, by the same laboratory technician. GH assay was determined by immunometric assay (Immulite; Diagnostic Products Corporation, Los Angeles, CA). The mean intrabatch coefficient of variation derived from the quality control serum included in the analytical runs was 6.1%. The GH mean serum levels from the first collection was 0.62 µg/liter (SD, 0.98), whereas from the second, it was 0.82 µg/liter (SD, 1.11). The intraclass correlation coefficient related to the two GH measurements was 0.86 (low-bound, 0.62). To test the reliability of individual categorical classification, GH values at two visits were transformed into ordinal data. The rank distribution of the second blood determinations compared with the rank distribution of the first blood determinations showed good agreement with a statistically significant (P < 0.01) Spearman rank correlation coefficient of 0.80. The good reliability of GH serum immunometric determinations indicates that single GH measurements may be indicators of GH individual categorization over a 1-year period.

Footnotes

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ The abbreviations used are: IGF, insulin-like growth factor; GH, growth hormone; IGF-I, insulin-like growth factor-I.

Received 10/ 5/01; revised 11/28/01; accepted 12/20/01.

References

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2. Mantzoros C., Tzonou A., Signorello L. B., Stampfer M., Tricopoulos D., Adami H. O. Insulin-like growth factor I in relation to prostate cancer and benign prostatic hyperplasia. Br. J. Cancer, 76: 1115-1118, 1997.[Medline]
3. Wolk A., Mantzoros C. S., Anderson S. O., Bergstrom R., Signorello L. B., Lagiou P., Adami H. O. Tricopoulos D Insulin-like growth factor I and prostate cancer risk: a population-based, case-control study. J. Natl. Cancer Inst. (Bethesda)., 90: 911-915, 1998.[Abstract/Free Full Text]
4. Harman S. M., Metter E. J., Blackman M. R., Landis P. K., Ma J., Wilkinson P., Hennekens C. H., Pollak M. Plasma Insulin-like growth factor I (IGF-I), IGF-II, IGF-binding protein-3, and prostate-specific antigen as predictors of clinical prostate cancer. J. Clin. Endocrinol. Metab., 85: 4258-4265, 2000.[Abstract/Free Full Text]
5. Hartman M. I., Veldhuis J. D., Thorner M. O. Normal control of growth hormone secretion. Hormone Res., 40: 37-47, 1993.[Medline]

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