If you've shied away from getting a colonoscopy to screen for
colorectal cancer, two new studies may make you less reluctant. One
study found that if a first colonoscopy is normal, patients can
safely put off having another test for at least five years - and
many experts would say at least 10 years. The other study found that
so-called virtual colonoscopies, which use CT scans, are roughly as
accurate as more intrusive colonoscopies at detecting dangerous
growths.
Put those two findings together with colonoscopies' proven
ability to detect cancers and pre-cancerous growths, and there's no
excuse for procrastinating.
In a standard colonoscopy, the doctor sedates a patient and then
inserts a long flexible tube with a tiny camera at its tip into the
rectum to view the interior lining of the colon. In a virtual
colonoscopy, the doctor uses a CT scanner to produce detailed images
of the colon's interior. No sedation is required. In both cases, the
patient has to take a laxative the day before to cleanse the colon
for proper examination.
A large multicenter trial of 2,600 patients in the United States
sponsored by the National Cancer Institute has just reported in The
New England Journal of Medicine that virtual colonoscopies detected
90 percent of the cancers and precancerous polyps that had been
detected by standard colonoscopy. The Cancer Institute deemed this
"comparable accuracy."
A second study, also supported by the government and reported in
The New England Journal, looked at patients who had returned for a
follow-up colonoscopy five years after getting a clean bill of
health. Not a single cancer was found among 1,256 patients at the
follow-up exam, and only a minuscule number of advanced polyps,
whose likelihood of becoming cancer is not known.
This study did not assess the effect of waiting 10 years between
standard colonoscopy screenings - the interval recommended by the
American Cancer Society and some professional guidelines - but the
failure to find a single cancer after five years suggests that the
10-year interval may be reasonable.
Colorectal cancer is the third most common cancer in the United
States, with an estimated 154,000 new cases last year, and the
second most lethal cancer, causing 52,000 deaths last year. Yet a
majority of Americans aged 50 or older fail to get screened. The
chief importance of the two new studies may be their potential to
entice more people to undergo screening that could save their lives.
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