Aspirin and Cancer — Barking Up the Right Tree



~ Dennis Morgan MD

Aspirin (acetylsalicylic acid) is derived from the bark of the willow tree, and it’s medicinal powers have been know for centuries. Recent evidence suggests it may prevent cancer. In this age of designer drugs and targeted therapy, this finding is a humbling reminder that mankind should not ignore nature’s bounty of botanical remedies.

The U.S. Preventive Services Task Force is at work on a final recommendation for the role of aspirin in reducing cancer risk. The NCI site lists four ongoing trials: CAPP3, ASCOLT, ASPREE, and AspECT and states that there are “No Easy Answers about Whether Aspirin Lowers Cancer Risk”(1).

Aspirin has been used for thousands of years to treat pain and fever. Synthesized in the mid-1800’s, it became the crown jewel of Bayer pharmaceutical. As the antipyretic drug of choice during the flu epidemic of 1918, it’s use at toxic doses contributed to the death count. With indications for heart attacks, strokes, pregnancy, diabetes, and dementia, aspirin is now credited with lowering the risk of colon and other cancers.

One seminal study is the 2011 paper in Lancet(2), from the Stroke Prevention Research Unit, University of Oxford. It looked at the correlation between daily aspirin use for stroke prevention and subsequent incidence of cancer: “These findings provide the first proof in man that aspirin reduces deaths due to several common cancers.”

The study involved 25,570 patients with 674 cancer deaths. After 5 years of follow-up the hazard ratio for aspirin use was 0.66 for all cancers and for gastrointestinal cancers, 0.46 (both p=0.003). As noted in an accompanying editorial(3)  “In a longer-term analysis … cancer mortality was 22% lower in participants randomised to receive aspirin for 5–9 years.” The benefits were ‘clear’ for colorectal cancer, ‘likely’ for esophageal, stomach and lung (adenocarcinoma) cancer, and ‘suggestive’ for prostate and pancreatic cancers.

The authors speculate on the role of COX-2 inhibition. Warfarin in the trials did not bestow protection from cancer, nor has, they claim, any platelet inhibitors other than aspirin. The study just cited had no funding by third parties.

A more recent Harvard study(4) also reported that aspirin reduces the incidence of colorectal cancer. The authors (one of whom had previously consulted for Bayer), evaluated the course over several decades of more than 130,000 persons enrolled in the Nurses’ Health Study and Health Professionals Follow-up Study. Presented in abstract at the 2015 Annual Meeting of the AACR, their conclusions differed from the above study — the magnitude of the effect was less, was limited to GI Cancers and appeared to be dose dependent, requiring sustained use of aspirin.

That willow bark extract can prevent cancer is plausible given the long history of success with botanicals in cancer medicine. Consider the Pacific yew (Taxol), Madagascar periwinkle (Vincristine) and Mandrake root (Etoposide), to name a few plants. Given the largesse of botanicals, it is alarming that we face the loss from neglect of hundreds of thousands of species, many yet to be discovered. The estimate of life’s diversity was recently refined by applying “asymptotic regression models to the temporal accumulation curves of higher taxa ”(5). There are about 8.7 Million eukaryotic species, 2.2 Million being in the oceans. Of these only 14% and 9% respectively have been described. (And that does not even account for prokaryotes (bacteria) from which come the anti-tumor antibiotics Adriamycin et al).

Do you think it is time to inform patients of aspirin as a cancer prevention option, particularly for colorectal cancer?

If you’re a physician, please join us inside SERMO as we continue to discuss Aspirin and cancer.



(1) No Easy Answers about Whether Aspirin Lowers Cancer Risk. National Cancer Institute site.

(2) Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trials. Rothwell PM et al. Lancet. 2011 Jan 1;377(9759):31-41.

(3) Will an aspirin a day help keep fatal cancer away? Jacobs EJ. Epidemiology Research Program, American Cancer Society.

(4). Long-term use of aspirin and risk of cancer. Cao Y et al. Abstract #876.  AACR Annual Meeting 2015.

(5) How Many Species Are There on Earth and in the Ocean? Mora C , et al. PLoS Biol 9(8): e1001127.

Figure 1. Modified from Janet Pope, botanical artist. ©Janet Pope.


Dennis Morgan MDDennis Morgan, MD is Assistant Clinical Professor University of Connecticut Health Center, Emeritus Staff Johnson Memorial Hospital and Medical Center Stafford CT and Past President Connecticut Oncology Association as well as Past Medical Director Phoenix Community Cancer Center, Enfield CT


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