Test Found to Miss Women’s Colon Cancer
A widely used screening technique for colon cancer, sigmoidoscopy, misses two-thirds of potential tumors in women, twice as many as it does in men, according to the first large study to compare use of the technique in the sexes.
Michigan researchers reported in today’s New England Journal of Medicine that precancerous polyps in women generally occur much higher up in the intestines, out of reach of sigmoidoscopes.
The researchers said doctors should use a more complete diagnostic method known as a colonoscopy to detect tumors in women.
The use of colonoscopies to screen for cancer has been growing because it is widely considered the gold standard for such testing.
But sigmoidoscopies, combined with fecal occult blood tests, are widely used because they can be performed by internists and general practitioners, they cost about a third as much as colonoscopies, they do not require sedation of the patient and they generally have been considered equally effective for men and women.
As a result, many insurance companies and managed care organizations do not pay for routine colonoscopies for either sex unless the patient is at elevated risk for tumors, such as when there is a family history of colon cancer.
If similar findings are made, “that certainly would impact future recommendations by the American Cancer Society and others,” said Dr. Durado D. Brooks, the society’s director of prostate and colorectal cancer. The cancer society’s guidelines recommend that patients talk to their physicians to learn about the options.
Dr. Eric Strom of the UCLA Medical Center, where men and women are routinely screened with colonoscopies, noted that using a sigmoidoscope to screen for colon cancer was “like doing mammography on only one breast.”
Colon cancer is the third-leading cause of cancer deaths in women, trailing only lung and breast cancers. An estimated 73,470 women will be diagnosed with the disease this year and 27,750 will die from it, according to the cancer society. A similar number of men will be affected, making it the second-leading cause of cancer deaths in this country overall, behind only lung cancer.
A 2001 study by researchers from the Department of Veterans Affairs found that the combination of fecal occult blood tests and sigmoidoscopies found about 70% of the precancerous polyps that were observed by colonoscopy. But men accounted for 97% of the more than 3,000 subjects in that study.
A team headed by Dr. Philip Schoenfeld of the University of Michigan Medical School and the Uniformed Services University of Health Sciences decided to conduct the study in women to compare the results with those from the 2001 study.
They studied 1,463 women, ages 50 to 79, at four military medical centers around the country. Researchers examined the entire 6-foot length of the women’s colons by colonoscopy, counting the number of polyps. Separately, they counted the number in the lower section of the colon, the area that would be reached by a sigmoidoscope. Researchers compared these results with those in the first study.
They found that men were nearly twice as likely to have advanced precancerous polyps, 8.6% compared with 4.9%. But if only sigmoidoscopy had been used in the women, the polyps would have been identified in 1.7% of women and missed in 3.2%, Schoenfeld said.
“That’s new information to me,” Strom said. “But it really doesn’t change what the state of the art is” -- to perform colonoscopies on all patents.
Schoenfeld and his colleagues also found that the number of polyps in the lower portion of women’s colons gave no indication of the number in the upper portion, as some researchers had thought it would, emphasizing the difference between men and women.
“With heart attacks and other diseases,” he said, “we know that men and women develop symptoms differently and require different approaches. Colon cancer screening should be no exception.”
