Nick Mulcahy

November 10, 2010

November 10, 2010 (Philadelphia, Pennsylvania) — The use of statins among a group of postmenopausal women did not reduce the risk for colorectal cancer, according to a new study from the landmark Women's Health Initiative (WHI).

"It's a difficult thing to do," said lead study author Michael S. Simon, MD, about attempting to evaluate the effect of statin use in the context of a trial like the WHI, in which only 7.6% of the 159,219 participants reported statin use.

"This is a "low prevalence of statin use," he said, adding that "groups with higher exposure may show a preventative effect."

Dr. Simon, who is a professor in the Department of Oncology at Wayne State University and Barbara Ann Karmanos Cancer Institute, Detroit, Michigan, presented the WHI results here at the Ninth Annual American Association for Cancer Research (AACR) International Conference on Frontiers in Cancer Prevention Research. He spoke to reporters at a meeting press conference.

In the WHI, the 2000 women diagnosed with colorectal cancer in a 10-year follow-up period amounted to a yearly incidence of 0.13% (or 13 cases per 10,000 person-years of follow-up) for statin users, and 0.12% for nonusers, reported Dr. Simon. "The upshot is that there was no significant difference in colorectal cancer risk," he said, adding that risk was evaluated after adjustment for other risk factors.

There was also no difference in risk by type of statin, location of the cancer, or other tumor characteristics.

Despite the findings, Dr. Simon said that colorectal cancer risk reduction was "biologically plausible" with statins. The drugs produce multiple "anticancer effects, such as inhibition of cell growth and promotion of programmed cell death," he said.

Nevertheless, Dr. Simon also said, in a press statement, that the negative findings "are consistent with the majority of the literature suggesting no significant reduction in colorectal cancer risk among users of statins." But he added that results from several case–control studies have shown a reduction in colorectal cancer risk in people who use statins, as did a case–control study from Northern Israel, which showed a 47% reduction in risk.

A future question for colorectal cancer researchers is whether or not "high-risk individuals" would benefit from statin use, said Dr. Simon at the press conference.

A Randomized Trial of Statins

A more definitive word about the effectiveness of statins in preventing colorectal growths will eventually come from a new randomized trial sponsored by the National Surgical Adjuvant Breast and Bowel Project (NSABP), suggested Scott Lippman, MD, who moderated the press conference at which Dr. Simon spoke.

Dr. Lippman is editor-in-chief of Cancer Prevention Research and professor and chair in the Department of Thoracic Head and Neck Medical Oncology at the University of Texas M.D. Anderson Cancer Center in Houston.

The NASBP trial, which is entitled Statin Polyp Prevention Trial in Patients With Resected Colon Cancer, is a phase 3 trial that compares the daily use of the statin rosuvastatin (Crestor, AstraZeneca) with placebo over 5 years in patients with recently resected stage I or II colon cancer.

"Our NSABP P-5 trial opened in late March of this year, and we have [institutional review board] approvals from more than 125 sites located throughout the United States and Canada," NSABP official, Larry Wickerman, MD, told Medscape Medical News.

Earlier this year at the AACR's annual meeting, a new study found that statins do not protect patients against colorectal adenomas, the benign growths that are precursors of colorectal cancer, and might even increase the risk of developing them when used for 3 years or more.

Those results were published in the May issue of Cancer Prevention Research (2010;3:588-596). In an editorial that accompanied the study (2010;3:573-575), a commentator said that there is "accumulating evidence that, at least overall, statins probably do not prevent colorectal neoplasia." However, there was a caveat in the editorial: "It is conceivable that there are benefits with high cumulative doses or in genetically defined subgroups."

More on the WHI Data

The statin–colorectal cancer risk study was a planned analysis in the WHI, said Dr. Simon.

The WHI study excluded women with previous colorectal cancer, and investigators recorded statin use and duration of use at the baseline screening interview of participating women. The data were updated at years 1 and 3. Colorectal cancer diagnoses were updated annually in women who participated in the observation group of the WHI, and semiannually in the women in the clinical trial group of the WHI, said Dr. Simon.

Some of the limitations of the WHI data include the facts that there was no requirement that participating women get screened for colorectal cancer and the fact that there was no information on statin dose, he pointed out.

Dr. Simon has disclosed no relevant financial relationships.

Ninth Annual American Association for Cancer Research (AACR) International Conference on Frontiers in Cancer Prevention Research. Abstract A59. Presented November 10, 2010.

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