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| |  Researchers Discover Strongest Known Risk Factor For Prostate Cancer TORONTO, ON -- January 23, 1998 -- Researchers at McGill University and the Harvard School of Public Health have found that an increased blood level of a specific hormone is a strong predictor of prostate cancer risk. These findings are published in this week's issue of Science and are funded, in part, by the Canadian Breast Cancer Research Initiative. The investigators found a four-fold increased risk of developing prostate cancer among men with the highest levels of a hormone called insulin-like growth factor-1 (IGF-1) compared to men who had the lowest IGF-1 levels. "We are excited about these results because this is one of the first studies showing clinical evidence of a relationship between IGF-1 levels and cancer," said Dr. Michael Pollak, professor of medicine and oncology at McGill University. "Until now, researchers interested in prostate cancer risk factors have focused on male hormones such as testosterone, but these results open up a whole new direction of research. "Our data shows a very strong relationship between IGF-1 levels and prostate cancer, making it the strongest known risk factor for prostate cancer. It's in the same order of magnitude as the relationship between cholesterol levels and the risk of getting heart disease." Dr. Pollak's laboratory is one of the few laboratories in the world examining the relationship between IGF-1 levels and cancer. Dr. Pollak's work, including this study, has been funded by the Canadian Breast Cancer Research Initiative, a unique partnership of the Canadian Cancer Society, the National Cancer Institute of Canada, the Medical Research Council, Health Canada and the private sector, including Avon Canada and the Royal Bank of Canada. For the past decade, Dr. Pollak has worked extensively in the laboratory with IGF-1, a hormone which plays a key role in the growth and development of children and, more specifically, in cell division. Dr. Pollak explained higher levels of IGF-1 may trigger a higher rate of cell division and proliferation, thereby making it more likely for a cellular genetic accident to occur, leading to cancer. In initial laboratory work, Dr. Pollak and colleagues focused on the relationship between breast cancer and IGF-1. They found IGF-1 to be as important as the female sex hormone estrogen in influencing breast cancer proliferation. Intrigued, Dr. Pollak decided to follow a hunch. He reasoned that since prostate cancer is also influenced by a sex hormone, testosterone, perhaps it might also be linked in some way to the IGF-1 hormone. "That's when our research took an unexpected turn," he said, adding that work exploring the link between breast cancer and IGF-1 is still continuing. "It's very interesting that work begun in breast cancer is giving us insights into prostate cancer. It would not be surprising if we find a lot of tumour biology that is common to both cancers." said Dr. Pollak, adding little progress has been made so far in identifying prostate cancer risk factors. The study examined previously collected and stored blood samples from a total of 304 men as part of the larger Harvard University School of Public Health Physicians' Health Study in Boston. In 1997, for this study, researchers measured and compared IGF-1 levels in 152 men who had been diagnosed with prostate cancer, and 152 males who did not have prostate cancer. Dr. Pollak said the study's findings have important implications for developing novel prevention and therapeutic strategies. There are drugs that can lower IGF-1 levels, he said, adding that further research will explore the possibility that these drugs might also decrease prostate cancer risk or be useful in prostate cancer treatment. Dr. Pollak noted that he is exploring whether lifestyle factors such as diet may also change IGF-1 levels. Dr. Pollak emphasized that different IGF-1 levels are related to a man's risk in getting prostate cancer, in contrast to PSA (prostate specific antigen) levels, which can indicate the presence of prostate cancer. (A higher than normal level of PSA could mean a man has prostate cancer or other prostate problems such as an infection.) In Canada, prostate cancer is the most prevalent cancer diagnosed in men. One in eight men will be diagnosed with prostate cancer during his lifetime. In 1997, it was estimated that 19,800 men were diagnosed with prostate cancer and that 4,100 of them died from prostate cancer. The main known risk factors for this cancer are age, race and family history, but with these new findings, IGF-1 appears to be more strongly associated with prostate cancer risk than any of these other previously known risk factors.
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