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Aspirin provides survival benefit as secondary preventative measure in colorectal cancer
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CHICAGO – Aspirin exposure after a colorectal cancer diagnosis improved OS and colorectal cancer-specific survival, according to study results presented at the ASCO Annual Meeting.
Regular aspirin use has been associated with a reduced incidence of colorectal cancer as well as reduced colorectal cancer mortality; however, using aspirin as a primary preventative agent remains debatable because of the serious risk for hemorrhage, according to study background.
Simer Bains, MD, a doctoral fellow at the center for molecular medicine at the University of Oslo, in Norway, and colleagues hypothesized that aspirin use as a secondary preventative measure for colorectal cancer may improve the risk–benefit profile. Researchers conducted this observational, population-based, retrospective study to examine the association between aspirin use after colorectal cancer diagnosis and OS and colorectal cancer-specific survival in a large cohort of patients.
“There were nine studies before ours looking at the same objective, and all except one showed that aspirin has a good effect,” Bains told HemOnc Today. “But the thing is these are all observational studies. So is ours, but what puts this study apart from the others is the size of the study population, that the population is unselected and the quality of the data material.”
Bains and colleagues used the Cancer Registry of Norway to identify 25,644 patients with colorectal cancer, 6,109 of whom were exposed to aspirin — defined as being prescribed aspirin for more than 6 months after colorectal cancer diagnosis — between 2004 and 2011.
The median follow up was 2.5 years.
Overall, 34.2% (n = 2,088) of the aspirin-exposed patients died, 56.1% of whom (19.2% of the total population) died from colorectal cancer.
Comparatively, 38.9% of patients with colorectal cancer who were not exposed to aspirin died, of which 83.7% (33.5% of the total population) were colorectal cancer-specific.
Results of a multivariable analysis indicated aspirin exposure post-diagnosis independently improved OS (HR = 0.86; 95% CI, 0.81-0.91) and colorectal cancer-specific survival (HR = 0.75; 95% CI, 0.70-0.81).
“The nature of these data is observational and retrospective,” Bains said. “It’s not randomized data, so, I’m still a little reluctant to advise my patients to use aspirin. But, you can make individual assessments with the patients because if they have, say, an increased risk for cardiovascular disease like hypertension, you can say they have two indications to use aspirin. Maybe it would set the bar a bit lower, but it’s important to remember the risk–benefit assessment because giving patients aspirin increases the risk for cerebral bleeding or gastric bleeding, so you have to weigh that against each other.”
Bains said there are three randomized controlled studies evaluating aspirin and that the results of those studies will help determine the overall benefit of aspirin in colorectal cancer.
“Our studies give a prospective indication of reality, but we still need to figure out which patients aspirin benefits the most,” Bains said. “It may be that not all patients should have aspirin. Can we find some biomarkers that are predictive? That should be our next step. We almost certainly know now that it has an effect, but we have not looked at entire populations. We have to stratify them to see if it’s useful for some patients and not all of them.” – by Anthony SanFilippo
Reference: Bains S, et al. Abstract 3504. Presented at: ASCO Annual Meeting; May 29-June 2, 2015; Chicago.
For more information: Simer Bains, MD, can be reached at simerjb@gmail.com.
Disclosure: Bains reports no relevant financial disclosures. One researcher reports consultant/advisory and leadership roles with PCI Biotech and Pfizer, stock ownership in LAURAS Immuno AS, and having provided expert testimony for Gilead Sciences.
Perspective
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Andrew Chan, MD, MPH
I think the study really adds to the body of evidence that supports the potential for aspirin as a treatment for patients with established colon cancer. Including that study, there have been six or seven studies that have shown that aspirin use is associated with a lower risk for dying from colon cancer in patients with colon cancer. It’s nice corroborating data. Another thing that makes it an interesting study is that it’s a large population and it’s an unselected population. The potential that this could be meaningful for a broad population of patients is quite high. Currently there are randomized clinical trials of aspirin in patients with established cancer that are already under way and I think those types of studies will be ultimately the type of gold standard evidence that will make this a more definitive finding. If we can really show in the setting of a randomized treatment study that aspirin improves survival, then this can find its way into the therapeutic armamentarium for all oncologists.
Perspective
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Marwan Fakih, MD
This Norwegian observational study confirms other prior findings that aspirin exposure following a diagnosis of colorectal cancer improves cancer-specific survival. Previously, the Nurse Health Study and Health Professionals Follow-up Study have reported a decrease in recurrence rate in subjects with colorectal cancer taking aspirin. In that study, COX-2 expression was associated with an increased likelihood of benefit. Other studies have reported an increased benefit from COX-2 inhibitors in decreasing colorectal cancer recurrence, especially in patients with PIK3-mutant colorectal cancer.
The strength of this retrospective observational study lies in the strength of the Norwegian registry, which collects outcome data on more than 99% of patients. The limitations of the study is the possibility of patient-driven use of aspirin that is not collected on the database. In addition, one cannot exclude the possibility of bias in aspirin use favoring more fit and lower risk individuals. Nonetheless, the decline in colorectal cancer mortality appears to be impressive and adds further support to an already existing body of evidence on the benefits of aspirin in colorectal cancer. The challenges moving forward would be to delineate which patients with colorectal cancer benefit the most from adding aspirin. Aspirin can increase the risk for gastrointestinal bleeding, which can be increased with antiangiogenic therapies and cytotoxic treatment commonly use in colorectal cancer patients. While the current data is intriguing, prospective clinical trials will be needed to better delineate the risks and benefits of aspirin in patients with a diagnosis of colorectal cancer. Some of these studies are ongoing. Meanwhile, oncologists should discuss risks of benefits of aspirin with their individual patients rather than implement aspirin use as a routine practice post-colorectal cancer diagnosis.
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