A new study published in JAMA this week has shown that in patients with colorectal cancer, taking an aspirin a day after diagnosis reduces the risk dying from the cancer or from any cause by at least 20%.  Taking aspirin before diagnosis, however, did not have any effect of prognosis.

It has been known for a few years that regular aspirin use can reduce the risk of developing colorectal cancer.  This drug isn’t a good idea as a preventive strategy though as it is associated with gastrointestinal irritation and bleeding – pretty serious side effects.  What this new study shows is that when it comes to colorectal cancer, aspirin might be just as effective and more practical as a treatment for people who already have the disease.

In this study, the authors first followed a whopping 170,000 health professionals for 20 years.  The 1279 men and women who developed colorectal cancer then completed a survey on aspirin use every two years for a further 7-10 years.

The majority of people who used aspirin reported taking the drug as an analgesic, mostly for headache or arthritis and other musculoskeletal pain.  A notable proportion, men in particular, took aspirin for cardiovascular disease prevention, which this handy little drug has also proved effective at.

Compared with participants who did not use aspirin, people who regularly used aspirin either after diagnosis only or both before and after diagnosis were 29% less likely to die from colorectal cancer and 21% less likely to die from any cause.  On the other hand, aspirin had no effect on mortality risks in people who took aspirin before cancer diagnosis only or both before and after diagnosis.

When the analysis was restricted to people who started taking aspirin after diagnosis only,  the risks of cancer-specific mortality and overall mortality were 47% and 32% lower than in those who didn’t take aspirin at all.  Conversely, there was no benefit seen specifically in the group that took aspirin before diagnosis and continued once they knew they had colorectal cancer.

The effect of aspirin in colorectal cancer was particularly strong in patients whose primary tumors overexpressed the enzyme cyclooxygenase 2 (COX-2), which crops up in about 80% of colorectal cancers, suggesting that aspirin might be an effective treatment in the majority of people with this type of cancer.  The amount of aspirin consumed also altered the effect – the mortality risk was slightly lower in people who took 6 or more tablets a week than in those who took 0.5 to five a week.

In an accompanying editorial, Alfred Neugut at Columbia University states that “aspirin may become standard adjuvant therapy in the management of colorectal cancer.” This treatment has the added advantage of being highly specific to are therefore only useful in patients with tumors that overexpress COX-2, so that “this potential future treatment comes with its own ready-made predictive biomarker.”

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Chan AT, Ogino S, Fuchs CS (2009) Aspirin Use and Survival After Diagnosis of Colorectal Cancer JAMA 302 (6): 649-658 LINK