Aspirin May Help Survival After Colorectal Cancer Diagnosis

Aspirin use after a colorectal cancer diagnosis was independently associated with improved rates of both cancer-specific and overall survival, according to the results of an observational, population-based study (abstract 3504) conducted in Norway. The study was presented by Simer Bains, MD, from the University of Oslo, at the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting held May 29 to June 2 in Chicago.

According to Bains, emerging evidence from observation studies, randomized trials, and experimental studies indicate that aspirin in a primary prevention setting reduces the incidence rate and mortality rate of colorectal cancer when used before diagnosis. However, the use of aspirin as a primary prevention is debated due to the risk of cerebral and gastrointestinal bleeding.

The use of aspirin as a secondary prevention has a different risk/benefit assessment, Bains said; therefore, in this analysis, she and colleagues assessed the use of aspirin after a colorectal cancer diagnosis.

In the study, the researchers linked data from patients diagnosed with colorectal cancer from 2004 to 2011 with the use of aspirin provided by the Norwegian Prescription Database. They defined aspirin exposure as having received a prescription for more than 6 months after diagnosis.

The study included 25,644 patients diagnosed with colorectal cancer, of whom 6,109 had aspirin exposure post-diagnosis; 19,535 patients were defined as non-users. Aspirin users were found to be an older and more frail group of patients, and were more likely to use potential confounding drugs such as metformin, statins, or ACE inhibitors.

Patients were followed for a median of 2.2 years, during which 34.2% of aspirin-exposed patients died (19.2% of deaths were colorectal cancer–specific). Among those patients with colorectal cancer who were not exposed to aspirin, 38.9% died, with 33.5% of the deaths classified as colorectal cancer–specific.

In the univariate analysis, no significant difference in overall survival was seen with aspirin use (hazard ratio [HR] = 1.03; 95% confidence interval [CI], 0.98–1.08). Bains said that this is likely due to the aspirin users being an older and slightly more fragile group of patients with a higher incidence of comorbidities.

When the researchers conducted a multivariate analysis and adjusted for factors such as age, gender, and tumor stage, they found that aspirin exposure improved cancer-specific death by 25% (HR = 0.75; 95% CI, 0.70–0.817; P < .001) and overall survival by 14% (HR = 0.86; 95% CI, 0.81–0.915; P < .001).

Bains said that the study did have several limitations, including the fact that the data were non-randomized and lacked information on over-the-counter use of aspirin. However, this use is limited as the packages are in small quantities, she explained.