Middle-aged men are twice as likely as women to end up with a cancer diagnosis after a colonoscopy, according to an Austrian study that challenges current screening guidelines.
Currently, people at average risk of colon cancer start screening for the disease at age 50, regardless of gender.
But the study, published in the Journal of the American Medical Association, shows a discrepancy of nearly 10 years between men and women in the development of colon and rectal tumors.
The study found that around 80 55-year-old men would need to undergo colonoscopies to spot one cancer, with the same true for 65-year-old women. The same logic held for the pre-cancerous growths called advanced adenomas, which doctors also look for during colonoscopies.
"Among a cohort of Austrian individuals undergoing screening colonoscopy, the prevalence and number needed to screen for advanced adenomas were comparable between men aged 45 to 49 years and women aged 55 to 59 years," wrote lead researcher Monika Ferlitsch, of the Medical University of Vienna.
But a US expert warned about making decisions regarding when to start screening based on the new findings.
The US Preventive Services Task Force (USPSTF), a federally supported expert panel, recommends colon cancer screening between the ages of 50 and 75 using one of a number of types of tests. The advantage of a colonoscopy is that it only has to be repeated once every ten years, as opposed to every year for the much cheaper stool test.
"I would discourage women from looking at this study and saying, 'Gee, I can wait longer.' And I would discourage men from saying, 'Gee, I should start sooner,'" said Michael LeFevre, at the USPSTF.
About one in 19 men develops colon cancer at some point and slightly fewer women do. The disease, which usually strikes older adults, is the third leading cause of cancer deaths in the United States.
For the study, Ferlitsch and her team looked at data from more than 44,000 Austrians who had had colonoscopies between 2007 and 2010.
Overall, they found 25 per cent of men had adenomas, compared to only 15 per cent of women. For full-blown tumors, those numbers were 1.5 per cent and 0.7 per cent, respectively.
At 0.8 per cent, the rate of colon cancer among men aged 50 to 54, for instance, was twice that found among women in the same age group. That means 125 men would need to have a colonscopy to find one tumor, versus 264 women.
While the reasons for the difference are still unclear, Ferlitsh said it could be linked to a higher degree of overweight and fatty liver disease among men, both of which have been linked to colon cancer.
While her team suggests that screening recommendations concerning age should be reconsidered, Ferlitsch wasn't ready to give advice.
"It's a difficult question if we should delay screening in women or start it earlier in men," she told Reuters Health.
LeFevre said the USPSTF will take the results into consideration as the panel updates its guidelines over the next couple of years.
For now, he said: "I think people can safely stick with the recommendation on the table to start screening at age 50, whether they are a man or a woman."