Screening can reduce colorectal cancer mortality, as
well as the incidence of the disease, but it is has been unclear which
screening method is the best.
Two long-term studies confirm the
effectiveness of major screening technologies, but leave the question of
superiority up in the air. Both appear in the September 19 issue of
the New England of Medicine.
In one study with a 22-year follow-up period,
colonoscopy was shown to have advantages over sigmoidoscopy for the prevention
of colorectal cancer. In addition, screening colonoscopy reduced the risk for
any colorectal-cancer-associated death, whereas sigmoidoscopy lowered the risk
of dying only from left-side tumors.
"Our data support the use of
colonoscopy as a the preferred screening option for patients if the primary
consideration is maximal reduction in risk of colorectal cancer," said
study coauthor Andrew Chan, MD, MPH, associate professor of medicine,
gastroenterology, at the Massachusetts General Hospital in Boston.
In the second study, which has a 30-year follow-up period,
annual and biennial screening with fecal occult blood testing reduced the risk
for death from colorectal cancer. The risk for death from colorectal cancer was
32% lower with annual screening, compared with no screening, and 22% lower with
biennial screening.
The Best Method?
But how does colonoscopy compare to fecal
occult blood screening?
Both of these tests are effective for
colorectal cancer screening, and both these studies support current screening
guidelines, according to an accompanying editorial by Theodore R. Levin, MD, and
Douglas A. Corley, MD, PhD, from Kaiser Permanente Medical Centers in
California.
In addition, the screening tests have improved
since the trial participants first used them.
The editorialists emphasize that these
studies are quite different from one another, which makes it difficult to make
direct comparisons of effectiveness.
"It would be tempting to use these 2
studies to draw conclusions about which test is more effective," they
write.
The reduction in mortality was better with
colonoscopy than with annual fecal occult blood testing (68% vs 32%). However,
it is a mistake to directly compare these results, the editorialists point out.
"The 2 study populations are not comparable: one was a randomized trial,
the other an observational study of volunteers, and both tests have undergone
improvements since the studies were performed."
To date, no completed studies directly
compare fecal occult blood testing with colonoscopy, although randomized trials
are ongoing.
Although the performance of colonoscopy
has probably improved because of the greater recognition of nonpolypoid
colorectal neoplasia, and it "appears to have a performance edge over the
old guaiac fecal occult blood test, fecal occult blood testing has largely been
replaced by the more effective fecal immunochemical test (FIT)," they
note. This newer test has better sensitivity than the guaiac fecal occult blood
testing used in that study.
Of importance, recent data show that
individuals were more likely to "complete screening if they were offered
guaiac fecal occult blood tests, a choice between colonoscopy and guaiac fecal
occult blood tests, or FIT alone, as compared with being offered colonoscopy
alone," they write.
In the Kaiser Permanente Northern
California health system, where both editorialists practice, a combined
approach is used, and substantial improvement in rates of colorectal cancer
screening has been achieved.
Colonoscopy vs Sigmoidoscopy
In the first study, Dr. Chan and colleagues evaluated the association
between the use of lower endoscopy (updated biennially from 1988 to 2008) and
colorectal cancer incidence (to June 2010) and mortality (to June 2012). The
cohort involved 88,902 individuals who participated in the Nurses' Health Study
and the Health Professionals Follow-up Study.
Over a follow-up period of 22 years, there were 1815 documented cases of
colorectal cancers and 474 colorectal-cancer-specific deaths.
When endoscopy screening was compared with no screening, multivariate
hazard ratios (HRs) for colorectal cancer were 0.57 after polypectomy, 0.60
after negative sigmoidoscopy, and 0.44 after negative colonoscopy.
A negative colonoscopy was associated with a reduced incidence of
proximal colon cancer (multivariate HR, 0.73), and the rate of mortality from
proximal colon cancer was lower after screening colonoscopy (multivariate HR,
0.47), but not after sigmoidoscopy.
The multivariate HRs for colorectal cancer mortality were 0.59 after
screening sigmoidoscopy and 0.32 after screening colonoscopy.
Even though colonoscopy appears to have some advantages over
sigmoidoscopy, there are reasons patients might opt for the latter. "A
screening sigmoidoscopy generally does not require a full bowel preparation or
the administration of sedation, so patients undergoing the procedure can
generally expect to miss less work," Dr. Chan told Medscape
Medical News.
"In addition, although serious complications from both colonoscopy
and sigmoidoscopy are quite rare — generally about 1 to 3 per 1000 patients —
they do occur at a higher rate with colonoscopy than with sigmoidoscopy,"
he noted.
Dr. Chan and colleagues point out that although randomized controlled
trials have shown that screening with flexible sigmoidoscopy reduces the
incidence of colorectal cancer and associated mortality, comparable data for
screening colonoscopy are not yet available.
"I think that, based on the data assembled so far and the
widespread availability of colonoscopy, we should continue our current practice
of recommending colonoscopy as one of a few screening options, with a full
discussion of the risks, benefits, and areas of uncertainty associated with
each test," said Dr. Chan.
Reduces Long-term Risk
In the second study, Aasma Shaukat, MD, MPH, from the University of
Minnesota in Minneapolis, and colleagues provide an update to the Minnesota
Colon Cancer Control Study, which assessed the long-term effect of fecal occult
blood test screening on all-cause and colorectal cancer mortality.
The initial cohort involved 46,551 participants 50 to 80 years of age
who were randomized to usual care or to annual or biennial screening with fecal
occult blood testing. Screening tests were performed from 1976 to 1982 and from
1986 to 1992.
The researchers used the National Death Index to obtain updated
information about the participants and to determine cause of death.
A total of 33,020 participants (70.9%) died from any cause during the
30-year follow-up period; 732 of the deaths were attributable to colorectal
cancer.
Table. Deaths From Colorectal Cancer in the Study Groups
Deaths
|
Annual Screening (n = 11,072)
|
Biennial Screening (n = 11,004)
|
Usual Care (n = 10,944)
|
n (%)
|
200 (1.8%)
|
237 (2.2%)
|
295 (2.7%)
|
Annual screening lowered colorectal cancer mortality (relative risk
[RR], 0.68), as did biennial screening (RR, 0.78). There was no reduction in
all-cause mortality with annual screening (RR, 1.00) or with biennial screening
(RR, 0.99).
Men 60 to 69 years of age got the most benefit from screening. RR for
death from colorectal cancer was 0.46 with annual screening, 0.42 with biennial
screening, and 0.44 for either screening.
The overall reduction in colorectal cancer death associated with
biennial screening was greater for men than women (P = .04 for
interaction). This difference was not observed with annual screening (P =
.30 for interaction) or with the 2 screening methods combined (P =
.06 for interaction).
"The reductions in colorectal cancer mortality in the Minnesota
Colon Cancer Control Study are comparable to those reported in randomized
clinical trials of screening with flexible sigmoidoscopy, suggesting that fecal
occult blood testing remains an effective and acceptable method of
screening," the authors write. "Stool-based tests for colorectal
cancer screening are an active area of current research, with development and
testing of new stool-based tests."
Tomado de: medscape.com
Referencia: N Engl J Med. 2013; 369:1095-1105, 1106-1114, 1164-1166
