Purpose: Statins have been shown to slow the growth of colon-cancer cells. Observational studies and secondary analysis from clinical trials have yielded inconsistent results on the relationship between statin use and the incidence of colorectal cancer. A meta-analysis in 2007 concluded that there was no preventive effect of Statins on colorectal cancer. The aim of this study was to evaluate the status of the relationship incorporating data from more recent studies.
Methods: A comprehensive search for studies published up to June 2010 was performed, reviews of each study were conducted, and relevant data were abstracted. Summary risk estimates with 95% confidence intervals were obtained using random effects meta-analysis. We also conducted a stratified analysis by study design. All studies were evaluated for publication bias before the analysis.
Results: Twenty four studies involving more than 1.7 million people were included in the analysis. There were twelve case-control, six cohorts and six clinical trials, six more studies since 2007. The average duration of statin use was 2.8 years. The overall relative risk estimate for CRC for statin use was 0.89 (95% CI 0.85 to 0.94; P<0.001). Interestingly, by study design, there was no evidence of reduction in incidence of CRC among clinical trials (RR 0.95, 95% CI 0.80 to 1.13, P>0.05). There was however 11% risk reduction (RR 0.89; 95% CI 0.85 to 0.94; P<0.001) and 14 % risk reduction (RR 0.86; 95% CI 0.79 to 0.94; P= 0.001) among the cohort and case control studies respectively. There was no evidence of publication bias.
Conclusion: The moderate risk reduction observed among observational studies is difficult to interpret given their inherent methodological limitations. On the other hand, results from clinical trials are based on secondary analysis. The role of statins in CRC chemoprevention is yet to be fully elucidated. A well designed trial hinging on agent-endpoint-cohort may be the answer.