Five years after a large study found that colonoscopy is the best way to detect early colon cancers in men, another has found that the same is true for women - only more so.
The reason: the less-invasive test that many patients prefer is likely to miss 65 percent of the precancerous growths that colonoscopy detects in women. In men, only a third would be missed.
"This means that it's even that much more important for women to use colonoscopy as their preferred tool for colorectal cancer screening," said Dr. Philip Schoenfeld, an assistant professor of medicine at the University of Michigan and lead author of the study in today's New England Journal of Medicine.
The simple explanation for the gender gap is that women are more likely to develop growths in portions of the colon beyond the reach of the shorter scope used in a simpler procedure called flexible sigmoidoscopy.
Schoenfeld said he can't explain why more women would have lesions farther up the colon, though hormonal differences could provide a clue.
Doctors performing a colonoscopy use a long scope to inspect and possibly remove abnormal growths that can turn cancerous. The scope stretches the full length of the colon - almost six feet - which is far enough to reveal the appendix tailing off the end. In contrast, sigmoidoscopies employ an instrument that is about one third as long.
Colon cancer is the fourth most common cancer in the United States, with about 148,000 new cases diagnosed annually. It is the second-leading cancer killer, claiming 56,000 lives.
Its incidence is slightly greater among men than women, though not enough to make it a "male cancer" or to justify less vigilance on the part of women, according to Schoenfeld and other experts.
Despite mounting evidence of colonoscopy's superiority, the American Cancer Society and other groups do not recommend it over other tools. Instead, the groups suggest that 50-year-old patients choose from four screening options: a colonoscopy, sigmoidoscopy, fecal occult blood test or barium enema.
The fecal occult test scans stool samples for microscopic evidence of blood that may have leaked from a tumor or polyp. In barium enemas, a test that has somewhat fallen out of favor, an X-ray of the colon is taken after barium sulfate is introduced.
Doctors in the women's study compared colonoscopy with a combination of flexible sigmoidoscopy and the fecal occult blood test.
