And laboratory studies had shown that insulin spurs growth of colorectal cancer cells, while IGFBP-1 inhibits their growth and spread.
This latest study involved 373 patients with non-metastatic (stage I-III) colorectal cancer diagnosed between 1991 and 2004.
Researchers looked at four proteins known to have a relationship to lifestyle factors, two with a stronger association and two with a lesser association. The two with the stronger association, one harmful (C-peptide) and one protective (IGFBP-1), turned out to be key.
Participants who had the highest levels of circulating IGFBP-1 had about a 50 percent reduced risk of dying, both overall and from colon cancer, compared with those who had the lowest levels of the protein, Wolpin said.
Meanwhile, those with the highest levels of plasma C-peptide had an 87 percent greater chance of dying overall and a 50 percent greater chance of dying from colon cancer than those with the lowest levels. The difference may be due to the fact that "C-peptide is basically insulin . . . and insulin clearly is correlated with heart disease and other things," Wolpin said.
"It doesn't mean we're going to give you a pill rather than tell you to exercise," Marshall said. "Instead of drug companies doing clinical trials, Nike should do them."
The American Cancer Society has more on risk factors for colon cancer.
SOURCES: John Marshall, M.D., chief, hematology/oncology, Georgetown's Lombardi Comprehensive Cancer Center, Washington, D.C.; Brian M. Wolpin, M.D., instructor, medicine, Harvard Medical School, attending physician, medical on
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