Sigmoidoscopy Exam of Boomers Age 55 to 64 Could
Reduce Colorectal Cancer Deaths by 43%
Two-thirds of cancers and growths are in the rectum
and lower colon, which can be examined by flexible sigmoidoscopy
There are 4 basic tests for colon cancer: a stool test (to check
for blood); sigmoidoscopy (inspection of the lower colon;
colonoscopy (inspection of the entire colon); and double
contrast barium enema. All 4 are effective in catching cancers
in the early stages, when treatment is most beneficial. More
from MedlinePlus below news story. More about Colorectal Cancer
at bottom of page.
April 28, 2010 - A single examination of the lower
colon and rectum using sigmoidoscopy, between the ages of 55 and 64
years, reduced colorectal cancer mortality by 43% in those screened, and
incidence by one third. These are findings of a very large long-term UK
study reported in an Article Online First and in an upcoming edition of
The Lancet.
The article is written by Professor Wendy Atkin,
Imperial College London, UK, and Professor Jane Wardle, University
College London, UK, and colleagues from the UK Flexible Sigmoidoscopy
Trial Investigators. The trial was funded by the UK Medical Research
Council, Cancer Research UK, The UK National Institute for Health
Research, and KeyMed.
Colorectal cancer is the third most frequently
diagnosed cancer worldwide, accounting for more than 1 million cases and
600 000 deaths every year.
Survival is strongly related to stage at
diagnosis, with survival rates of 90% for localised cases. Current
screening methods using the faecal occult blood test, which detects
early cases, reduce mortality by around 15%, and many countries have
introduced screening programmes based on this test.
Study finds very few seniors given this option and
when they do it is for a less toxic treatment - see video. Second report
looks at cost of colon cancer care.
There
could be an overall colorectal cancer mortality reduction of 50 percent
by 2020; rates declined most among senior citizens over 65 and increased
most in people under age 50
Cancer's precursor polyps, known as adenoma, sharply
increase after age 50
Below
story see...
>Medicare's coverage of tests for colorectal cancer.
>More about colon cancer.
Sept. 3, 2008 People over age 50, who are still
wrestling with the decision of whether they should have a colonoscopy,
received another wake-up call this week from a study detailing the rapid
increase of polyps the precursor of virtually all colorectal cancers
that begin to occur at that age.
Read more...
Most colorectal cancers arise from adenomas:
predominantly symptomless growths that develop in 20% of the population.
Two-thirds of colorectal cancers and adenomas are
located in the rectum and sigmoid (lower) colon, which can be examined
by flexible sigmoidoscopy.
The authors of this study proposed that one
flexible sigmoidoscopy screen undertaken between ages 55 and 64 years is
a cost-effective and acceptable method to reduce colorectal cancer
incidence and mortality. Their hypothesis is based on observations
suggesting that most people who develop a distal colon cancer will have
developed an adenoma by 60 years of age, and that removal of adenomas by
sigmoidoscopy provides long-term protection against the development of
distal colorectal cancer.
Recruitment and screening were started in November,
1994 and completed in March, 1999. The study took place in 14 UK
centres: 11 in England, two in Wales, and one in Scotland. Baseline
findings from the trial were published in 2002, and in this Article the
authors report the results after a median of 11 years of follow-up.
Participants underwent flexible sigmoidoscopy with
polypectomy for small polyps* and referral for colonoscopy if there were
polyps meeting any of the following high-risk criteria: 1 cm or larger;
three or more adenomas; tubulovillous or villous histology; severe
dysplasia or malignant disease; or 20 or more hyperplastic (benign)
polyps above the distal rectum. Individuals who had no polyps or only
low-risk polyps at flexible sigmoidoscopy were discharged.
A total of 170,432 eligible men and women, who had
indicated on a previous questionnaire that they would accept an
invitation for screening, were randomly allocated to intervention
(flexible sigmoidoscopy screening) or control groups. The primary
outcome was the incidence of colorectal cancer, including prevalent
cases detected at screening.
The control group consisted of 113,195 and 57,237
to the intervention group, of whom 112,939 and 57,099, respectively,
were included in the final analyses.
A total of 40,674 (71%) people underwent flexible
sigmoidoscopy.
During screening and median follow-up of 11 years,
2,524 participants were diagnosed with colorectal cancer (1818 in
control group vs 706 in intervention group) and 20,543 died (13 768 vs
6775; 727 certified from colorectal cancer [538 vs 189]).
In intention-to-treat analyses (which included
people assigned to screening but who did not attend), colorectal cancer
incidence in the intervention group was reduced by 23% and mortality by
31%. Incidence of distal colorectal cancer (rectum and lower colon) was
reduced by 50%. Incidence of colorectal cancer in people attending
screening (excluding non-attendees) was reduced by 33% and mortality by
43%. The numbers needed to be screened to prevent one colorectal cancer
diagnosis or death, by the end of the study period, were 191 and 489,
respectively.
The authors say: "After 11 years of follow-up,
colorectal cancer incidence was reduced by a third and colorectal cancer
mortality by more than 40% in those who underwent screening. Confining
results to the rectum and sigmoid (lower) colon, incidence was reduced
by half in those who were screened."
Furthermore, they point out that 59% (126) of the
215 colorectal cancer cases that developed were detected at screening
and very few cases were detected post screeningsuggesting that
screening has a lasting protective effect.
The researchers also add that results of previous
case-control studies suggested that flexible sigmoidoscopy could reduce
distal colon cancer incidence and mortality by around 70%. They say: "So
far the cumulative reduction in people attending screening in our study
is 50%.
This lower value is most likely attributable to
dominance of screen-detected prevalent cancers in the first four years
of follow-up, and only after this point did a benefit in terms of
incidence reduction become apparent. If incidence in the screened
participants remains low during further follow-up, the magnitude of the
incidence reduction will continue to increase."
While the study recorded no effect of screening on
the upper or proximal colon, sigmoidoscopy does not examine the upper
colon so this result could be expected. Only the 5% participants with
high-risk polyps were referred for more complete colonoscopy
examination.
The authors add: "Rates of all-cause mortality
excluding colorectal cancer were slightly, although not significantly,
reduced in the intervention compared with the control group. This
reassuring finding suggests that the screening did not have unexpected
harms."
They continue: "Economic analyses suggest that,
with pre-existing assumptions, a once-only flexible sigmoidoscopy screen
at age 55 or 60 years would be cost saving, largely because of the
avoided costs of treatment resulting from the reduction in incidence...
Our study population is representative in terms of risk of colorectal
cancer and there is no reason to believe that the potential benefits of
screening would differ in people who chose not to participate."
They conclude: "The results from our trial show
that flexible sigmoidoscopy is a safe and practical test and, when
offered only once to people between ages 55 and 64 years, confers a
substantial and longlasting protection from colorectal cancer."
In an accompanying Comment, Professor David F
Ransohoff, Department of Medicine and Epidemiology, University of North
Carolina at Chapel Hill, NC, USA, says that although sigmoidoscopy
screening is not perfectly protective, "the good news is that this size
of benefit is large for any cancer screening test, certainly compared
with mammography for breast cancer or assay of prostate-specific antigen
for prostate cancer".
"Perhaps even greater reduction for screening
sigmoidoscopy will be observed after more follow-up in the UK and
Norwegian randomised trials, because long follow-up is needed to account
for the 'prevalent (screen detected) colorectal cancers [that] dilute
any incidence reducing effect of polypectomy', as well as to detect
mortality reduction, he added.
More frequent endoscopy might lead to still
greater reductions in colorectal cancer, as may be assessed in the US
randomised trial of screening sigmoidoscopy repeated at 5 years. In
2010, the UK randomised study must be regarded as the most reliable
evidence about the size of the reduction in colorectal cancer for 10
years after endoscopic examination of the left [lower] colon."
About
Sigmoidoscopy by MedlinePlus Enclyclopedia
Sigmoidoscopy
Sigmoidoscopy is an internal examination of
the lower large bowel (colon) and rectum, using an instrument
called a sigmoidoscope.
How the Test is Performed
During the test, you are positioned on your
left side with your knees drawn up toward your chest. A
gastroenterologist or surgeon will perform the test. First, the
doctor does a digital rectal exam by gently inserting a gloved
and lubricated finger into the rectum to check for blockage and
to dilate (gently enlarge) the anus.
Next, the sigmoidoscope - a hollow tube
through which the doctor can see - is inserted into the rectum.
Air is introduced into the colon to expand the area and help the
doctor see better. The air may cause the urge to have a bowel
movement.
The sigmoidoscope is advanced, usually as
far up as the sigmoid colon or descending colon. Then, as the
scope is slowly removed, the lining of the bowel is carefully
examined. The hollow channel in the center of the scope allows
for the passage of forceps for taking
biopsies or for other instruments for therapy.
Sigmoidoscopy may be done using a rigid or
flexible scope. Ask your doctor which procedure you are having.
Cancer of the colon or rectum is also called
colorectal cancer. In the United States, it is the fourth most common
cancer in men and women. Caught early, it is often curable.
It is more common in people over 50, and the risk
increases with age. You are also more likely to get it if you have
● Polyps - growths inside the colon and rectum
that may become cancerous
● A diet that is high in fat
● A family history or personal history of colorectal cancer
●
Ulcerative colitis or
Crohn's disease
Symptoms can include blood in the stool, narrower
stools, a change in bowel habits and general stomach discomfort.
However, you may not have symptoms at first, so screening is important.
Everyone who is 50 or older should be screened for colorectal cancer.
Colonoscopy is one method that your doctor can use to screen for
colorectal cancer. Treatments for colorectal cancer include surgery,
chemotherapy, radiation or a combination.
What Are the Key Statistics for Colorectal Cancer?
Excluding skin cancers, colorectal cancer is the
third most common cancer diagnosed in both men and women in the United
States. The American Cancer Society's most recent estimates for the
number of colorectal cancer cases in the United States are for 2009:
● 106,100 new cases of colon cancer (52,010 in
men and 54,090 in women)
● 40,870 new cases of rectal cancer (23,580 in
men and 17,290 in women)
Overall, the lifetime risk for developing
colorectal cancer is about 1 in 19 (5.2%). This risk is slightly higher
in men than in women. A number of other factors (described in the
section,"What
are the risk factors for colorectal cancer?") may also affect a
person's risk for developing colorectal cancer.
Colorectal cancer is the third leading cause of
cancer-related deaths in the United States when men and women are
considered separately, and the second leading cause when both sexes are
combined. It is expected to cause about 49,920 deaths (25,240 in men and
24,680 in women) during 2009.
The death rate (the number of deaths per 100,000
people per year) from colorectal cancer has been dropping for more than
20 years. There are a number of likely reasons for this. One is that
polyps are being found by screening and removed before they can develop
into cancers. Screening is also allowing more colorectal cancers to be
found earlier when the disease is easier to cure. In addition, treatment
for colorectal cancer has improved over the last several years. As a
result, there are now more than 1 million survivors of colorectal cancer
in the United States.
Participants underwent flexible sigmoidoscopy with
polypectomy for small polyps* and referral for colonoscopy if there were
polyps meeting any of the following high-risk criteria: 1 cm or larger;
three or more adenomas; tubulovillous or villous histology; severe
dysplasia or malignant disease; or 20 or more hyperplastic (benign)
polyps above the distal rectum. Individuals who had no polyps or only
low-risk polyps at flexible sigmoidoscopy were discharged.