Aug 04, 2014
Statins, the widely used drugs taken to lower cholesterol, might have another benefit—increasing survival among patients diagnosed with colorectal cancer. That’s according to a Journal of Clinical Oncology (JCO) study, published online, ahead of print, August 4.
The study, “Statin Use After Diagnosis of Colorectal Cancer and Survival: A Population-based Cohort Study,” funded by the Northern Ireland Public Health Agency, was motivated by previous research showing that statins may deliver a blow to cancer by inhibiting cancer cell growth, triggering the death of those cells, and impeding the proliferation of blood vessels that cancer cells need to grow. The study also took its cue from studies suggesting that statins can significantly reduce rates of recurrence and death among patients with breast and prostate cancer.
According to the study’s first author, Chris R. Cardwell, PhD, a Senior Lecturer in Medical Statistics at Queens University in Belfast, Northern Ireland, this study helps build the case for future research.
“Some of the rationale behind our study was to inform the decision of whether or not it is worthwhile to carry out a randomized, controlled trial, which would give the definitive answer about the benefit of statins on colorectal cancer survival,” said Dr. Cardwell.
A study design that accounted for biases
Previous studies have also looked at the connection between survival and use of statins among patients with colorectal cancer. However, these studies contained a few methodological problems. For one, the sample sizes of those studies were small, ranging from 308 to 842 patients. In addition, one of the prior studies did not account for a knotty methodological issue called, “immortal time bias,” which refers to this problem: Patients who live longer are more likely to receive medications.
Dr. Cardwell shed further light on this statistical bias.
“The problem is, say you follow a group of people who have a specific cancer diagnosis,” said Dr. Cardwell. “After four or five years, some will die and some will still be alive. The people who die early have less opportunity to get a medication of interest. If you then naively compare survival in people who ever used a medication with those who never used it, the medication will appear protective because the people who live longer are more likely to get it.”
The JCO article sought to address some of these methodological issues. It included 7,657 patients diagnosed with colorectal cancer between 1998 and 2009, making it the largest study to date looking at statin use and colorectal cancer survival. English cancer patients were identified from the National Cancer Data Repository, which was linked with the U.K. Clinical Practice Research Datalink.
The study also accounted for such methodological problems as “immortal time bias.”
“The statistical analysis in our study was conducted using methods recommended to account for this bias,” said Dr. Cardwell.
The study found that patients who took statins had a 29% reduction in their rates of death due to colorectal cancer, when compared to patients who did not use statins. Furthermore, the longer a patient took statins, the greater the reduction in rates of death, so that those who took the medication for less than one year had a 21% reduction, while those on the medication for more than one year had a 36% reduction.
Dr. Cardwell cautioned that the study does not mean that every colorectal cancer patient should be given a prescription for statins on their way out of doctors’ offices. First, researchers need to carry out randomized controlled trials to determine the true effect of statins on cancer recurrence in colorectal cancer patients by studying survival in groups of statin users and non-users randomly allocated to have identical characteristics.
“There’s still some inconsistency in the observational studies on the association between statin use and cancer survival,” said Dr. Cardwell. “I think further observational studies are required to see if other groups can confirm this association. If it were confirmed, then it would provide a strong rationale for a randomized controlled trial.”
Chris R. Cardwell is a Senior Lecturer in the Centre for Public Health at the School of Medicine, Dentistry and Biomedical Sciences, Queens University, Belfast, Northern Ireland.
Abstract of the original JCO article
PDF of the original JCO article
Cardwell, CR, Hicks, BM, Hughes, C, et al. Statin use after diagnosis of colorectal cancer and survival: a population-based cohort study. J Clin Oncol. 2014. Published online ahead of print 8.4.2014.
The Exclusive Coverage series on ASCO.org highlights selected research from JCO with additional perspective provided by the lead or corresponding author.
@ 2014 American Society of Clinical Oncology