Aspirin in colorectal cancer – a new trick for an old dog

AspirinA 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.”

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

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1 Comment

  1. So it seem like aspirin will not only reduce the risk of you getting colorectal cancer, but also improve your survival if you’re unlucky enough to get the disease. But wait, taking aspirin before diagnosis – i.e. as a preventive measure – means that the drug is less effective as a treatment after diagnosis?

    Perhaps aspirin before diagnosis lowers the risk of getting a COX-2 positive tumour, so those people who take preventive aspirin yet still get colorectal cancer actually tend to get COX-2 negative tumours, which aren’t susceptive to aspirin.

    The authors actually say something to this effect:
    “COX-2–positive tumors may be relatively sensitive to the anticancer effect of aspirin, whereas COX-2–negative tumors may be relatively aspirin-resistant. Moreover, [our findings] potentially explains the observation that the benefit of postdiagnosis aspirin use on patient survival was not apparent among patients who used aspirin prior to cancer diagnosis”

    I’m still not sure of what I should be doing, but the nasty gastrointestinal effects of aspirin use put me off testing the anticancer effects of the drug myself.

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