NEW YORK (Reuters) -- A new test that can predict a man's risk of prostate cancer may be on the horizon, according to new findings released Friday.
The test measures insulin-like growth factor-1 (IGF-1), a growth factor known to stimulate growth and inhibit death in normal and cancerous prostate cells. The net effect of this growth factor is to increase the likelihood of mutations in prostate cells, then to protect the mutated cells from programmed cell death, the body's natural mechanism for ridding itself of dysfunctional cells.
A team of investigators led by epidemiologist Dr. June M. Chan of Harvard School of Public Health in Boston, Massachusetts, used data collected on men enrolled in the national Physicians' Health Study to see if IGF-1 levels were linked to prostate cancer risk in humans as they are in the laboratory.
The investigators used blood samples obtained pre-diagnosis to measure IGF-1 and prostate-specific antigen (PSA) in 152 men diagnosed with prostate cancer during the study and in 152 age-matched controls. The PSA level is regularly used by physicians as an early-detection test for prostate cancer.
"Regardless of whether men had a PSA level above or below 4, which is the clinical cutoff..." for prostate cancers likely to advance if untreated, "...the results were very consistent," Chan told Reuters. The data revealed a significantly increased risk of prostate cancer in men with the highest levels of IGF-1, compared with those with the lowest levels. According to the report, men with the highest levels had a 4.3-fold increased risk of prostate cancer compared with those who had the lowest IGF-1 levels.
Though the findings have no immediate clinical implications, Chan said that her team hopes their report will "spur additional research" on the predictive value of IGF-1 in prostate cancer. According to a commentary in Science, the senior author of the study, Dr. Michael Pollak of McGill University in Montreal, Quebec, Canada, and colleagues have already "...found an equally strong association between IGF-1 levels and the risk of breast cancer, and they are now seeking links to colon cancer."
Chan told Reuters that if the link between IGF-1 and prostate cancer is confirmed, "...IGF levels could be used to help identify men who are at risk before they develop cancer." By contrast, she said that PSA levels are most useful in predicting disease progression in men already diagnosed with prostate cancer or its precursors. In addition, the findings may lead to new research into dietary or pharmaceutical interventions that can reduce IGF-1 levels, and potentially prevent the development of prostate cancer.
SOURCE: Science (1998;279:475, 563-566)
LONDON (AP) -- Young women with elevated levels of a particular growth hormone have a risk of breast cancer seven times higher than those with low levels, according to study published Friday.
The research is the first to find a link between this natural substance, called insulin-like growth factor, or IGF-1, and the chance of breast cancer in pre-menopausal women. It raises the possibility that doctors someday might screen for this hormone to help identify those at higher risk of the disease.
American and Canadian researchers, led by Dr. Susan Hankinson of the Brigham and Women's Hospital in Boston, say further studies with greater numbers of women are needed to better define the risk before a course of action can be recommended.
But if confirmed by subsequent research, the results, published in this week's issue of The Lancet, a British medical journal, could help doctors determine which women to monitor most closely to catch the disease early, said Dr. Debu Tripathy, a cancer specialist at the University of California in San Francisco.
If doctors can confirm that lowering hormone levels really does have an effect and can figure out how to achieve that result, they may be able to prevent breast cancer altogether, he said.
IGF-1, a hormone produced by most tissues in the body, is involved in normal growth but also helps cancer grow once the disease has set in. It was linked to prostate cancer in a similar study published in January.
Hankinson used blood samples of women taken in 1989 and 1990 before any of them was diagnosed. Over the next five years, the level of IGF-1 was measured in the original blood samples of the 397 women who later developed breast cancer and compared with the levels in the original samples of those 620 women who did not.
The scientists found that among the 76 pre-menopausal women, those with IGF-1 concentrations in the highest category had almost three times the risk of those with levels in the lowest category.
And among pre-menopausal women younger than 50, the risk of breast cancer for those with the highest levels of the hormone was about seven times more than for their counterparts with the lowest levels.
"The up to sevenfold increase suggests that the relation between IGF-1 and risk of breast cancer may be greater than that of other established breast cancer risk factors, with the exception of a strong family history of breast cancer or a high-density mammographic profile," the study said.
The scientists found no association between the concentration of IGF-1 and the risk of breast cancer in post-menopausal women.
The study did not consider whether the higher hormone levels cause the disease.
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Last modified: 8 May 1998