In the name of God

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.

FATDiet 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 case-control and cohort studies.

CHOLESTEROL2 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