Statins May Not Lower Colorectal Cancer Risk

A new study suggests that cholesterol levels rather than cholesterol-lowering statin drugs may actually be responsible for the decrease in colorectal cancer.

Prior studies have provided evidence that those who take statins regularly have a decreased risk of colorectal cancer. This new observational analysis of medical records of over 100,000 patients shows that a so-called indication bias-a confusion between cause and effect when exposure to an agent is dependent on an indication, in this case high cholesterol-could explain the previous connection between statin use and the reduction in colorectal cancer risk.

The new results are published in PLOS Medicine.

Using the Health Improvement Network, a database of electronic records of over 10 million patients in the United Kingdom, Ronac Mamtani, MD, MSCE, assistant professor of hematology/oncology at the Abramson Cancer Center and the Perelman School of Medicine of the University of Pennsylvania, and colleagues compared statin use and blood cholesterol levels between 22,163 patients with colorectal cancer and 86,538 patients without colorectal cancer.

The researchers found that although the risk of colorectal cancer was lower among individuals who used statins compared to those who did not, when researchers compared patients who had continued, long-term statin use to those who discontinued statin use, there was no longer a difference in risk (odds ratio [OR], 0.98 [95% confidence interval, 0.79–1.22]), suggesting that a bias may explain the initial association.

Increased serum cholesterol was also independently associated with a decreased risk of colorectal cancer (OR, 0.89 per mmol/L increase). This link was only present if serum cholesterol was measured within 6 months of a cancer diagnosis (OR, 0.76), and was no longer present after 24 months (OR, 0.98). 

The analysis also showed that decreases in total serum cholesterol by > 1 mmol/L at least a year before a colorectal cancer diagnosis was linked with a 1.25-fold and 2.36-fold increased risk of colorectal cancer among statin users and non-users, respectively.

"Together, these data demonstrate a complex association between statins, cholesterol, and colorectal cancer, suggesting that unexplained cholesterol lowering in statin users or nonusers may be a marker of undiagnosed colorectal cancer,” the study authors stated. The authors noted that statins should not be prescribed for colon cancer prevention and that unexplained decreases in blood total cholesterol should alert physicians to consider whether the presence of colon cancer could explain the change.

"Clinical judgment should be used when considering causes of cholesterol reduction in patients, including those on statin therapy,” the authors concluded.