Screening cannot account for the gains in colorectal cancer prevention
Over the past 40 years the incidence of colorectal cancer has dropped a dramatic 40% in the US and deaths from the disease have fallen by more than half
But before clinicians start patting themselves on the back, they should examine the underlying forces driving this trend, or so argues a recent commentary in The New England Journal of Medicine.
According to the authors, screening alone cannot account for the gains in colorectal cancer prevention.
Research shows that screening using FOBT and sigmoidoscopy results in only a 5% to 18% reduction in incidence of colorectal cancer and a 14% to 28% reduction in mortality.
“None of the trials of colorectal cancer screening has shown a 50% reduction in mortality – nor have trials of screening for any type of cancer,” the authors wrote.
While earlier detection and improved treatments went some way to explaining the decrease in mortality, fewer cases of colorectal cancer were developing in the first place, they said.
Changes to diet were one obvious explanation, specifically reduced consumption of smoked and cured meats.
Changes in the microbiome secondary to widespread antibiotic use was another, while HRT, aspirin and NSAIDS might also have a role in reducing colorectal neoplasia.
In Australia, the mortality rate from CRC has halved between 1968 and 2012, however the incidence rate has remained steady during the same period.
Professor Michael Solomon, head of the department of colorectal surgery at the University of Sydney, said the rapid increase in life expectancy in Australia meant the lifetime risk of common cancers also increased. Treatments for colorectal cancer had improved, and there was a trend towards earlier detection.
