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EPIDEMIOLOGY OF
COLORECTAL CANCER
Mohsen Janghorbani
Professor of Epidemiology
Isfahan University of Medical Sciences
INTRODUCTION
98% adenocarcinoma.
1/2 CRC in rectum and rectosigmoid,
1/4 in sigmoid, 1/4 in caecum,
ascending, transverse and descending
colon.
3/4 of primary CRC will also have
benign adenoma.
WORLWIDE INCIDENCE FOR CRC
Incidence varies in different region of
the world, increased in N. America,
W. Europe, Australia, New Zealand.
Higher incidence in industrialized areas,
8.5% of all new cancer cases diagnosed
worldwide.
Groups that move to high risk areas
assume the risk of that geographical
region.
DESCRIPTIVE
EPIDEMIOLOGY
Gender
Age
Ethnic/ race
Socio-economic status
Geographical distribution
High risk areas include North
America, Europe and Australia.
Low risk areas include Central and
South America, Asia and Africa.
ESTMATED RATES OF CRC INCIDENCE BY
GENDER AND AREA
SECULAR TRENDS
The numbers of new cases of
colorectal cancer worldwide has
increased rapidly since 1975.
RISK FACTORS
Genetic
Environmental factors
GENETIC FACTORS
Familial adenomatous polyposis.
Hereditary non-polyposis CRC.
History of CRC in first degree relatives
Inflammatory bowel disease (Crohn and,
specially, ulcerative colitis).
DIETARY AND NUTRITIONAL
PRACTICE
Energy intake
Meal frequency
Adult height
High body mass
Physical activity
Carbohydrates
Extrinsic sugars
DIETARY AND NUTRITIONAL
PRACTICE
Fat and cholesterol
Protein
Alcohol
Vitamins
Minerals
Foods and drinks
ENERGY INTAKE
• Total energy intake has no simple relationship
with CRC risk, but its effect may be
dependent on levels of obesity and physical
activity. Whatever the reason, the data on
energy intake and CRC are inconsistent; no
judgment is possible.
MEAL FREQUENCY
• 5 case control studies have shown a
small increase in risk (10 to 20%)
associated with each daily eating
occasion.
• Frequent eating possibly increases the
risk of CRC.
ADULT HEIGHT
4 cohort studies have found an increase
risk in association with greater stature
and colon cancer. In contrast, case
control studies have found no
association between height and CRC.
Being tall as an adult possibly increase
the risk of CRC.
BODY MASS INDEX
One cohort and 4 case-control studies
were null.
3 cohort and 8 case-control studies
found positive results.
Obesity possibly increases risk of
CRC, particularly in men, but perhaps
not rectal cancer.
PHYSICAL ACTIVITY AND
COLON CANCER
Of 9 cohort study only 2 reported no
substantial association.
Of 11 case-control studies only 1 study
reported increased risk.
The evidence that physical activity, specially
when life-long, decrease the risk of colon
cancer, is convincing, but not for rectal cancer.
PHYSICAL ACTIVITY AND
RECTAL CANCER
2 cohort study reported higher level
of activity are associated with weak
increase in risk of rectal cancer.
Of 7 case control studies 4 reported no
substantial association.
The evidence relating to physical
activity, and the risk of rectal cancer is
more limited and inconsistent; no
judgment is possible.
Carbohydrates
Evidence on diet high in starch and
the risk of CRC is rather inconsistent.
Diet high in starch possibly decrease
the risk of CRC.
EXTRINSIC SUGARS
One cohort and 8 case-control studies
have shown the diet comparatively
high in refined sucrose are associated
with increase risk of CRC. 4 further
studies found no or weak association.
Diet high in extrinsic (refined) sugars
possibly increase risk of CRC.
Evidence is strongest for sucrose.
FIBER
Data from prospective study weakly
supportive of fiber hypothesis.
2 meta analysis of 13 and 16 case
control studies provided evidence for
a linear reduction in CRC.
Diets high in fibers possibly decrease
the risk of CRC.
FAT
Diet high in total fat or saturated fat
possibly increase the risk of CRC.
The evidence on mono- or
polyunsaturated fat and CRC is
inconsistent; no judgment is possible.
This evidence is obtained from ecological
studies, animal experiments, and casecontrol and cohort studies.
CHOLESTEROL
2 cohort studies found no association.
One meta-analysis of 13 case control
studies of CRC found a weak increase in
risk.
An ecological study reported a positive
correlation between cholesterol and colon
cancer mortality.
In 9 of 11studies egg consumption was
associated with the risk of colon cancer and
with rectal cancer in 6 of 8 studies.
CHOLESTEROL
The evidence suggests that dietary
cholesterol may increase the risk of CRC
but the overall picture is also consistent
with no association, no judgment is
possible.
PROTEIN
5 cohort studies and 8 of 15 case
control studies found no association.
The epidemiological evidence for an
association of protein with CRC is
inconsistent; no judgment is possible.
ALCOHOL
High alcohol consumption probably
increase the risk of CRC. The effect
generally seems to be related to total
ethanol intake irrespective of the type of
drink.
VITAMINS
High dietary carotenoid intake
possibly decreases the risk of CRC.
High dietary vitamin C, E, folate, and
methionine intake may reduce the
risk of CRC; but the evidence is, at
present, insufficient.
MINERALS
Evidence suggests that vitamin D may
reduce the risk of CRC; but the
evidence is, at present, insufficient.
The evidence on calcium suggest that
there may be a very week overall
reduction in risk but the conservative
judgment is that there is possibly no
relationship.
MINERALS
Dietary selenium is possibly unrelated
to the risk of CRC.
The evidence suggest that iron intake
may increase the risk of CRC , but is,
as yet, insufficient.
FOODS AND DRINK
The evidence suggests that cereals may
reduce the risk of CRC; but are
currently insufficient.
The evidence on roots and tubers
including, especially potato, is
inconsistent, no judgment is possible.
FOODS AND DRINKS
Evidence that diets rich in vegetables
protect against CRC is convincing. The
data on fruit are more limited and
inconsistent; no judgment is possible.
The evidence relating to pulses and the risk
of CRC, is inconsistent, no judgment is
possible.
FOODS AND DRINKS
The evidence relating to nuts and
seeds and the risk of CRC is very
limited, no judgment is possible.
The evidence shows that red meat
probably and processed meat possibly
increases risk of CRC.
FOODS AND DRINKS
The data on poultry consumption are
inconsistent; it may be that poultry has no
relationship with CRC, but no judgment is
possible.
Diet high in fish possibly have no relationship
with the risk of CRC.
FOODS AND DRINKS
Consumption of eggs possibly increases
risk of CRC.
The evidence on the relationship between
CRC and dairy products is inconsistent,
no judgment is possible.
The evidence suggests that coffee may
decrease the risk of CRC but is, as yet,
insufficient.
FOODS AND DRINKS
The data on the relationship between
chlorinated drinking water and CRC are
inconsistent; no judgment is possible.
Cooking meat at high temperature
possibly increases the risk of CRC.
HORMONE REPLACEMENT
THERAPY
Increasing evidence supports an
association between hormone
replacement therapy and a reduced risk
of colorectal cancer.
Of 19 published studies of hormonal
replacement therapy and risk of
colorectal cancer, 10 support an inverse
association and a further five show a
significant reduction in risk.
ASPIRIN AND NSAID
A substantial body of evidence
supports a protective effect of aspirin
and other nonsteroidal
antiinflammatory drugs on the
development of colon cancer.
SMOKING
Cigarette smoking is associated with
an increased tendency to form
adenomas and develop CRC.
CONCLUSION
The evidence that diets high in vegetables
and regular physical activity decrease the
risk of CRC, is convincing.
Alcohol, and consumption of diets high in
red meat, probably increase the risk of
CRC.
CONCLUSION
Diets high in starch, non-starch
polysaccharides (fiber) and carotinoids
all of which possibly decrease risk of
CRC.
Obesity, adult height, frequent eating,
and diet high in sugar, total and
saturated fat, eggs, and processed meat,
all possibly increase risk of CRC.
CONCLUSION
Established non-dietary causes of CRC
include genetic predisposition, ulcerative
colitis, infection with Schistosoma sinesis
and smoking .
Aspirin and NSAIDs decrease risk of
CRC.
THANK YOU