Blood tests for CRP are typically used as a non-specific marker for
infection and inflammatory conditions. A more sensitive CRP test
(hs-CRP) can help determine heart disease risk.
Prior studies suggested an association between elevated CRP levels
and colon cancer, which fits with the hypothesis that chronic inflammation increases cancer risk. But due
to small population sizes and mixed results of the studies, the
relationship between CRP and colon cancer risk remains controversial.
"Although cancer-induced inflammation has been proposed to explain
the relationship between elevated CRP levels and cancer risk, this
hypothesis has not been well evaluated in previous studies," said Yang, a
research associate professor of Medicine. "This study, the largest
study thus far on circulating CRP and colorectal cancer risk, allows us
to test this hypothesis in a more definitive manner."
Yang and colleagues measured CRP levels in blood samples from women
participating in the Shanghai Women's Health Study, a large
population-based prospective study of nearly 75,000 Chinese women.
In an analysis of 209 cases of colon cancer and 279 healthy controls,
the researchers found that women with CRP levels in the highest
quartile (the upper 25 percent) had a 2.5-times greater risk of colon cancer compared with women in the lowest
quartile.
To examine if there is a causal relationship between blood CRP levels
and colorectal cancer risk, they stratified the samples by the time
intervals between blood sample collection and disease
diagnosis.
They found that the increased risk was primarily seen in women with
high blood CRP levels measured within the three years prior to
diagnosis. As the interval between the blood draw and cancer diagnosis
increased, the association between CRP levels and risk faded.
Because the increased risk associated was greatest in the first years
after CRP measurement, Yang believes that high CRP levels may arise
largely from the patient's inflammatory response to cancer. Therefore,
high CRP may be more of a "risk marker" (something that is detectable as
a result of disease) rather than a "risk factor" (something that
predisposes one to disease).
Yang will present the results of this study during a press conference
on Monday, April 19 at 1:00 p.m. in room 142 of the Washington D.C.
Convention Center, during the AACR annual meeting.