Aspirin cuts risk of inherited bowel cancer by half and its effect can last for over 10 years, find experts
A regular dose of aspirin to reduce the risk of inherited bowel cancer lasts at least 10 years after stopping treatment, according to a new study. The international trial, known as CAPP2, involved patients with Lynch syndrome from around the world and revealed that two aspirins a day, for an average of two-and-a-half-years, reduced the rate of bowel cancer by half.
Bowel cancer is cancer in any part of the large bowel (colon or rectum). It is also known as colorectal cancer and might be referred to as colon cancer or rectal cancer, depending on where it starts. Lynch syndrome is associated with an increased risk of colorectal cancer and with a broader spectrum of cancers, especially endometrial cancer. The study, led by experts at the Universities of Newcastle and Leeds, UK, involved 861 patients with Lynch syndrome, which affects about one in 200 people in the population. These people have a genetic problem with DNA repair, putting them at much higher risk of cancers such as bowel and womb. In the study, the 861 genetically susceptible patients were randomized to have either aspirin or placebo for two to four years and followed up for 10-20 years.
A group of 427 were randomized to take aspirin continuously for two years and 434 were allocated to placebo. They were all followed up for 10 to 20 years. Long-term results of the trial showed that 600 mg of aspirin daily reduced colorectal cancer risk by half compared to those on placebo. The results of the study are statistically interpreted that aspirin reduced the risk by about 50%, and the efficacy lasted for 10-20 years after taking the medication, says Professor Jukka-Pekka Mecklin from the University of Jyväskylä and Central Finland Hospital District, in the analysis. "Participants were followed for a mean of 10 years approximating 8,500 person-years. 40 (9%) of 427 participants who received aspirin developed colorectal cancer compared with 58 (13%) of 434 who received placebo," says the study published in The Lancet.
Findings showed that when all original recruits were included in the study, those on aspirin had 42% fewer colon cancers. Among those who took the aspirin for a full two years, there were 50% fewer colon cancers. "It took a long time to start the trial and to recruit enough people in 16 countries, but this study has finally given us an answer. Two aspirins a day for a couple of years give protection that lasts more than 10 years and the statistical analysis has become much stronger with time. For people at high cancer risk, the benefits are clear, aspirin works," says Professor Sir John Burn, from Newcastle University and Newcastle Hospitals NHS Foundation Trust, who led the research.
Explaining the study further, researchers said that between 1999 and 2005, participants began either taking two aspirins every day for two years or a placebo. At the end of the treatment stage in 2007, there was no overall difference between those who had taken aspirin and those who had not. However, the research team anticipated a longer-term effect and designed the study for continued follow-up. By 2010, there had been 19 new bowel cancers among those who had received aspirin and 34 among those on placebo. The incidence of cancer among the group who had taken aspirin had halved, and the effect began to be seen five years after patients started taking the aspirin.
"Aspirin has a major preventative effect on cancer but this doesn't become apparent until at least four years later. With the help of these dedicated volunteers, we have learned something of value to us all. Before anyone begins to take aspirin regularly, they should consult their doctor first as aspirin is known to bring with it a risk of stomach complaints, including ulcers and bleeding. However, if there is a strong family history of cancer, then people may want to weigh up the cost and health benefits of taking aspirin for at least two years," says Professor Burn.
The research team is now conducting a new international trial, CaPP3, with more than 1,800 people with Lynch syndrome enrolled to look at whether smaller, safer doses of aspirin can be used to help reduce the cancer risk.