IGF-1 LEVELS AND CANCER MORTALITY

NEW YORK (Reuters Health) Feb 11 - Serum levels of insulin-like growth factor-1 (IGF-1) are associated with cancer mortality risk in older men, according to a January 15th online report in The Journal of Clinical Endocrinology & Metabolism.

"This is the first study to show an association of higher levels of circulating IGF-1 with increased risk of cancer mortality over a long follow-up," Dr. Gail A. Laughlin from the University of California, San Diego in La Jolla told Reuters Health in an email.

"If confirmed in several other studies, IGF-1 measurements might be useful in cancer screening, but assays will need to be standardized and cutpoints established," Dr. Laughlin said. "Much research remains to be done."

In the meantime, she and her coauthors say, "These results suggest caution in the use of IGF-1-enhancing therapies to slow the adverse effects of aging."

Dr. Laughlin and her colleagues examined the association of serum IGF-1 levels with cancer mortality in 633 men over 50 years old (mean age, 73 years). From their baseline clinic visits in 1988-1991 through 2006, 368 men died, including 74 (20%) who died of cancer.

Median baseline IGF-1 levels were significantly higher in men who died of cancer (109 ng/mL) than in those who did not (95 ng/mL), the authors report.

IGF-1 levels showed a significant quadratic (nonlinear) association with cancer mortality, and multivariate analyses revealed a significant association of higher levels of IGF-1 with a progressively higher risk of cancer death after adjustment for body-mass index, IGF binding protein-I, waist-to-hip ratio, physical exercise, current smoking, and previous cancer.

The adjusted risk of cancer death ranged from 1.61-fold higher for IGF-1 levels from 120-159 ng/mL to 2.61-fold higher for levels from 200-239 ng/mL, compared with levels below 120 ng/mL.

Similarly, the risk of cancer death was 82% higher for the 46% of men whose IGF-1 level was at or above 100 ng/mL than for those with lower IGF-1 levels.

J Clin Endocrinol Metab 2010.