Long-term, regular aspirin use linked to lower colorectal cancer mortality
Long-term, regular use of aspirin before diagnosis appeared associated with lower colorectal cancer-specific mortality, according to results of an observational study published in Journal of the National Cancer Institute.
Peter Campbell, MSc, PhD, scientific director in the department of population science at American Cancer Society, and colleagues pursued the research, in part, because one study published last year suggested increased colorectal cancer mortality with aspirin use. Additionally, they wanted to help health care providers and colorectal cancer survivors make educated decisions regarding lifestyle and behavior that could affect long-term prognosis.
“We were interested in seeing if we’d observe harm or benefit in a much larger, observational study [and we had] been broadly interested in lifestyle and behavioral factors that may influence prognosis among [colorectal cancer] survivors for about a decade,” Campbell told Healio. “It’s important to provide additional information for clinicians and [colorectal cancer] survivors to help make informed decisions.”
The analysis included 4,071 adults from the Cancer Prevention Study-II Nutrition cohort who were cancer-free at baseline (1992 or 1993) and subsequently diagnosed with invasive colon or rectal cancer by end of follow-up (June 30, 2015). The mean age at colorectal cancer diagnosis was 73.5 years.
After excluding those without data on aspirin use, Campbell and colleagues followed 2,686 adults with data on pre-diagnosis aspirin use and 1,231 adults with data on post-diagnosis aspirin use for mortality outcomes through December 2016. Overall, 512 of the former group and 251 of the latter group died of colorectal cancer.
Results showed long-term regular use of aspirin, defined as taking it at least 15 times per month, before diagnosis was associated with lower colorectal cancer-specific mortality (HR = 0.69; 95% CI, 0.52-0.92).
Although results suggested post-diagnosis regular aspirin use was not statistically significantly associated with risk for colorectal cancer-specific mortality overall (HR = 0.82; 95% CI, 0.62-1.09), participants who began regular aspirin use only after their diagnosis exhibited lower risk than participants who did not use aspirin during both the pre-and post-diagnosis periods (HR = 0.6; 95% CI, 0.36-0.98).
In a secondary analysis, Campbell and colleagues evaluated pre-diagnosis aspirin use and stage at diagnosis (distant metastatic vs. localized or regional). Results showed long-term aspirin use prior to diagnosis was associated with lower odds of diagnosis with distant metastases (OR = 0.73; 95% CI, 0.53-0.99).
“We thought it was really interesting that pre-diagnosis aspirin use was associated with lower odds of distant metastatic disease,” Campbell said. “It’s exactly part of the story for what we hypothesized would explain the lower mortality, but it’s always exciting when a hypothesis is supported by empirical data.”
Although the observational study would need additional research to confirm the findings, “we think some of this benefit in terms of survival comes from aspirin’s ability to inhibit micrometastases, likely through aspirin’s effect on platelet inhibition,” Campbell said.
“Cancer guidelines aren’t formulated from any singular study, this one included, [but] in the absence of contraindications to taking aspirin, this study at least does not suggest it’s potentially harmful to take aspirin post-diagnosis,” Campbell added.
Campbell and colleagues acknowledged that their analysis was limited by the inability to examine associations stratified by tumor molecular features, as previous studies suggested an association of aspirin use with colorectal cancer risk and mortality could be modified by various molecular features of the tumor. Additionally, the researchers noted they had incomplete information on medication usage, and the results may be confounded by unaccounted risk factors.
“In terms of future research on this topic, there are a few randomized, clinical trials that should be finishing up in the next 2 or 3 years,” Campbell said. “It’ll be curious to see if those results show a bona fide impact of aspirin on [colorectal cancer] survival.”
For more information:
Peter T. Campbell, MsC, PhD, can be reached at 250 Williams St. NW, Atlanta, GA 30303; email: email@example.com.