Before It's Too Late

A new technique will allow early 

detection of prostate cancer, says Biplab Das 

If lung cancer is a smoker's nightmare, prostate cancer is a nightmare for non-smokers. It usually occurs among elderly men, and is detected by a blood test. A positive test usually reveals high level of prostate specific antigen (PSA). The PSA test can detect cancer only in its late stages when malignancy has already set in. 

To find a suitable alternative to the PSA test, a team of researchers from Harvard and McGill universities has come up with a molecule that rings an early warning bell. In a recent issue of Science, they wrote that men whose blood has high levels of a protein called insulin-like growth factor I (IGF I) were four times more likely to develop prostate cancer than men with lower IGF-I levels. "Of all the associations with prostate cancer we have looked at, this is the strongest," says Ann Hsing, an epidemiologist, at the National Cancer Institute. 

An IGF test helps to identify potentially aggressive tumours at an early stage giving patients enough time to access proper medication. "We are not suggesting that this report allows us to determine clinical practice," says Michael Pollak, a clinical oncologist at McGill University in Montreal. 

Before providing treatment, mass screening is necessary, which is not cost effective. Though PSA test spots some cancers early, it often leads to unnecessary surgeries. Under these circumstances, researchers turned to IGF-I to see if it could be used to detect prostate cancer. From laboratory studies, they knew that the molecule stimulates the growth of both cancerous and normal cells. To verify IGF's role in prostate cancer, the team studied men enrolled in the physicians' Health Study at Harvard. They found that men with high levels of IGF-I were four to three times more likely to have developed prostate cancer than men with lower IGF-I levels. 

Rather than being co-conspirator, IGF-I is suspected to be solely responsible for prostate cancer. This finding triggered further studies. A Stanford team surgically removed prostates to know tumour traits that predict aggressive disease, notes Donna Peehl, a tumour biologist at Stanford Medical School. Peehl is eager to see the correlation between IGF-I levels and tumour's aggressive nature. "A paper like this which is so provocative, raises a whole spectrum of question," says cancer epidemiologist David Schottenfeld of the University of Michigan School of Public Health. Being a growth factor, IGF-I exerts influence on many tissue types, which is guiding researchers to look at other cancers. 

In more recent experiments, Pollak and colleagues have come up with stunning results that IGF-I is strongly associated with breast cancer. They are hoping to link it to colon cancer. IGF-I may well be the indicator of several other cancers as well. And the next round of research will determine that.