April 22, 2004 - Could a simple blood test help identify people at risk for some of the most commonly diagnosed cancers? A newly published analysis offers this hope, and a cancer prevention expert who spoke to WebMD says it could be a reality in just a few years.
The study, a review of earlier studies, found high blood levels of insulin-like growth factor-1 (IGF-I), a traditional marker for growth hormone, may be linked to a modest increase in the risk for colorectal cancer, prostate cancer in men, and breast cancer among women diagnosed prior to menopause. It did not appear to increase breast cancer risk in postmenopausal women, however.
"Circulating IGF-I and IGFBP-3 (may) have a role in cancer risk assessment and prevention," lead researcher Andrew G. Renehan, PhD, and colleagues write in the April 24 issue of the journal The Lancet.
Better Prevention Targeting
The findings suggest that by measuring levels of these proteins in the blood, health professionals may one day be better able to target cancer interventions to appropriate populations, says McGill University director of cancer prevention Michael Pollak, MD.
"We are not saying that we know that measuring IGF-I will be useful for this, but this is the next phase of research," he tells WebMD. "I think that we will certainly have some answers within the next few years."
The association may also help explain why some populations are at higher risk for certain cancers. African-American men, for example, have a high incidence of prostate cancer, and they tend to have higher-than-normal IGF-I levels, Pollak says.
In the newly published analysis, researchers reviewed 21 studies involving 3,609 people with cancer and 7,137 people without cancer. They found that the risk for developing prostate cancer was roughly 50% higher in men with the highest levels of IGF-I than in those with the lowest. A 65% increase in breast cancer risk was reported for premenopausal women, and elevated IGF-I levels were associated with about a 20% increase in colorectal cancer risk for both sexes.
Pollak says even though these increases are modest, they findings are potentially useful because so many people have elevated levels of these proteins.
"About a fourth of the population has elevated IGF-I," he says. "In the absence of other established risk factors, it may be that these people have the most to gain from interventions to prevent cancer."
Growth Hormone Supplementation
The findings may also give pause to people who take growth hormones in supplement form. The body makes less and less growth hormone as a person ages, and many people now take supplements to boost their natural levels in the belief that this will keep them young. Growth hormone increases the level of IGF-I.
"Ads for these products are all over the Internet," Alicja Wolk, PhD, of Stockholm's Karolinska Institute, tells WebMD. "Anyone can get them, but we know very little about the consequences of their long-term use."
Pollak agrees, adding that he believes that long-term use among people who are not growth hormone deficient increases cancer risk.
"There is certainly a precedent for hormones causing cancer," he says. "Body builders who take androgens have a higher risk of developing liver cancer, and we know that women who take estrogen have a small but significantly increased risk for breast cancer. I believe that people who maintain elevated growth hormone levels for five or 10 years increase their cancer risk."