Young adults without a family history of bowel disease
are unlikely to develop adenomas, the
colorectal polyps most likely to lead to cancer, according
to new research directed by scientists at the
Johns Hopkins Kimmel Cancer Center. The finding
supports current cancer screening guidelines
recommending that adults in general undergo screening
colonoscopies starting at age 50.
The new study, published in the September issue of the
journal Clinical Gastroenterology and
Hepatology, also showed that white patients more often
had adenomas on the left side of the colon,
whereas African-Americans had lesions more often on the
right side. The take-home lesson, the
researchers said, is that screening and diagnostic
evaluations of African-Americans should include a
colonoscopy rather than a sigmoidoscopy because the latter
evaluates only part of the colon.
The Johns Hopkins study assessed the "natural history"
and occurrence of colorectal polyps by
reviewing records of 3,558 autopsies performed at The Johns
Hopkins Hospital between 1985 and
2004 on patients aged 20 to 89. The review, called an
"epidemiologic necropsy," categorized patients
by sex, race and 10-year age groups, then compared the
prevalence and location of adenomas between
younger adults (ages 20 to 49) and older adults (ages 50 to
The review identified a low but increasing prevalence
of colorectal adenomas — from 1.72
percent to 3.59 percent — from the third to the fifth
decade of life, with the presence of adenomas
sharply increasing after age 50. Prevalence ranged from 10
percent to 12 percent from the sixth to
ninth decade of life.
"Our study affirmed that the greatest increase in
prevalence was in older adults, abruptly
starting in the sixth decade," said Francis M. Giardiello,
professor of medicine, oncology and
pathology, who directed the research. The average number of
adenomas spotted in most young adults
was one. In older adults, the average number of adenomas
ranged from 1.6 to 1.9.
Most polyps detected in colorectal screenings qualify
as adenomas, but there are also lower-risk
lesions called "hyperplastic," which are not thought to
lead to cancer, the researchers noted.
The researchers found that in young adults, adenomas
were slightly more prevalent in men than
in women, and in whites than in blacks. In older adults,
the prevalence of adenomas also was greater in
men than in women, but greater in blacks than in whites.
In addition, the study found that in both younger and
older adults, the overall prevalence of
left-sided adenomas was higher than right-sided adenomas.
Compared with younger adults, older
adults had an increased prevalence of adenomas on both
sides of the colorectum but a relatively
greater prevalence of right-sided adenomas.
Colorectal cancer is the second leading cause of
cancer-related death after lung cancer. Each
U.S. citizen has a 6 percent lifetime risk of colorectal
cancer. When colorectal cancer is diagnosed at
an early stage, five-year survival rates are about 90
percent, but less than 40 percent of patients
present at an early stage.
The study was supported by the John G. Rangos Sr.
Charitable Foundation, the Clayton Fund and
the National Institutes of Health.
Co-authors were Cheryl J. Pendergrass, Daniel L.
Edelstein, Linda M. Hylind, Blaine T. Phillips,
Christine Iacobuzio-Donahue, Katharine Romans and Constance
A. Griffin, all of Johns Hopkins; Marcia
Cruz-Correa, of the University of Puerto Rico, San Juan;
and Anne C. Tersmette and G. Johan A.
Offerhaus, of Utrecht Medical Center, the Netherlands.