Three new studies published in the journals The Lancet and The Lancet Oncology on Tuesday add to the evidence that a daily dose of ASA, or acetylsalicylic acid, might be able to prevent cancer as well as stop it from spreading.
Previous studies have noted that daily use of ASA over a period of about a decade can reduce the risk of bowel and other common cancers. However, some experts have hedged those findings with concern about side effects, since ASA -- commonly sold as aspirin -- can sometimes cause stomach bleeding.
These latest studies, led by Oxford University's Dr. Peter Rothwell and colleagues from the John Radcliffe hospital, looked at data from 51 studies involving more than 70,000 people.
The studies were designed to test the use of daily ASA versus no ASA in patients at risk of heart attacks and other vascular events. Doctors often instruct such patients to take a dose of 75 milligrams of ASA per day to help guard against strokes and heart attacks.
The researchers found that those patients who took low doses of ASA taken daily for at least three years had a lower risk of developing cancer: 23 per cent lower in men and 25 per cent lower in the women.
Those taking the ASA had a 15 per cent lower risk of dying from any kind of cancer compared to those not taking the drug. The longer that patients took ASA, the more powerful it appeared to become: for patients who took the drug for longer than five years, their chance of developing cancer dropped by 37 per cent.
In a second study, the drug was also found to slow the march of cancer to other organs. Known as metastasis, that spread is often lethal to patients suffering from the disease.
The data suggest that ASA can reduce the metastasis of spreading cancers by 36 per cent by keeping them localized.
Aspirin thins out the blood, meaning its ability to clot is restricted. More than 40 years ago, scientists experimenting with mice showed that platelets were a key factor in the spread of cancer. Scientists now believe ASA's effects on blood platelets is key.
Carolyn Gotay, a professor from the University of British Columbia's School of Population & Public Health, says it appears that prolonged use is important to the desired effect.
"It's clear you really need to take aspirin every day for a long time. This is not something you can take now and again -- you have to make a commitment," she said.
Gotay added that she will discuss the findings with the Canadian Cancer Society.
While ASA can increase the chance of bleeding in the brain, intestines and stomach, experts believe that it should still factor into national cancer prevention strategies. Data also shows that the risk of bleeding declines after three years of use.
In the United Kingdom, experts are already pressing the issue with health officials in a bid to roll out an official public campaign. But public health agencies are weighing the findings with previous data on the side effects.
With a report from CTV's medical specialist Avis Favaro and producer Elizabeth St. Philip
