NEW YORK (Reuters Health) – For people in their 80s and
90s, the risks of colonoscopy appear to outweigh the benefits,
investigators report in the Journal of the American Medical
Association. The slow development of colorectal cancer means
that these patients are more likely to die of other causes,
even if cancer is identified.
Meanwhile, for average-risk individuals, the decreased risk
of developing colorectal cancer after a normal result on an
initial colonoscopy remains lower than that of the general
population for more than 10 years, according to a second study
published in JAMA.
Current guidelines do not include an age at which
colorectal cancer screening with colonoscopy should be stopped,
Dr. Otto S. Lin and his associates note, even though the
procedure is associated with higher complication rates among
the very elderly.
Physicians need to consider whether the risk and cost of
screening colonoscopy can be justified by potential benefits in
very elderly patients, Lin’s team notes.
The investigators evaluated data for 1,034 symptom-free
individuals, 50 to 54 years of age, 147 between 75 and 79 years
of age, and 63 who were at least 80 years of age. The subjects
all underwent colonoscopy at Virginia Mason Medical Center in
Seattle between 2002 and 2005.
The rate of tumors increased with age, from 3.2 percent
among the youngest group to 14 percent among the oldest group.
However, screening colonoscopy added little to the lifespan of
the older patients, just 0.13 years.
These findings should help doctors and patients “decide
whether screening colonoscopy should be performed and help
avoid its use in patients who are unlikely to benefit
substantively,” Lin and his associates conclude.
In the second paper, a group led by Dr. Harminder Singh
points out that the interval for screening colonoscopy that has
been widely adopted is based on the estimated time required for
a polyp to transform into cancer. However, the average duration
of lowered risk of colorectal cancer risk after a normal
colonoscopy is not known.
To estimate this risk over time, Singh and colleagues at
the University of Manitoba in Winnipeg evaluated cancer
diagnoses and cancer-related deaths reported in the Manitoba
Cancer Registry and the Manitoba Health Population Registry.
This included 32,203 individuals with normal colonoscopy
results and who had been followed for more than 6 months.
The results showed that even after 10 years, people with
normal colonoscopy results had a lower cancer risk than people
in the general population. This suggests that a screening
interval of longer than 10 years may be appropriate.
In a related editorial, Dr. Timothy R. Church, from the
University of Minnesota School of Public Health in Minneapolis,
reminds readers that the benefits of screening were originally
based on trials of stool blood testing, rather than on much
more expensive strategies.
He estimates that at a cost of $500 per colonoscopy,
screening 10 percent of individuals 50 years or older in the US
every year would cost more than $4 billion annually.
SOURCE: Journal of the American Medical Association, May
24/31, 2006.
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