9887basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]

By

Basem Salama Eldeek MSc,MD,MHPE

Associate prof of community medicine Faculty of medicine king Abdulaziz university,KSA

And mansoura university ,Egypt.    

Acknowledgement

•  The study of the factors affecting cancer, as a way to

infer possible trends and causes.

•  The study of cancer epidemiology uses epidemiological

methods to find the cause of cancer and to identify and

develop improved treatments.

•  This area of study must contend with problems of

•  lead time bias

•  length time bias.

•  Lead time bias is the concept that early

diagnosis may artificially inflate the

survival statistics of a cancer, without

really improving the natural history of

the disease.

•  Length bias is the concept that slower growing, more indolent tumors are more likely to be

diagnosed by screening tests, but improvements in

diagnosing more cases of indolent cancer may not

translate into better patient outcomes after the

implementa t ion o f sc reen ing p rograms .

•  A similar epidemiological concern is overdiagnosis,

the tendency of screening tests to diagnose diseases

that may not actually impact the patient's longevity.

This problem especially applies to prostate cancer

and PSA screening.

•  Some cancer researchers have argued that negative

cancer clinical trials lack sufficient statistical power

to discover a benefit to treatment.

•  Observational epidemiological studies that show

associations between risk factors and specific

cancers mostly serve to generate hypotheses

•  Randomized controlled trials then test whether

hypotheses generated by epidemiological studies

and laboratory research actually result in reduced

cancer incidence and mortality.

•  Programmatic trials.

Robert A. Weinberg, "If we lived long enough, sooner or later we all would get cancer."[10]

•  Over a third of cancer deaths worldwide are due to potentially

modifiable risk factors

§  Tobacco smoking, lung cancer, mouth, and throat cancer;

§  Drinking alcohol, oral, esophageal, breast, and other cancers;

§  A diet low in fruit and vegetables,

§  Physical inactivity, colon, breast,

§  Obesity, is associated with colon, breast, endometrial

§  Sexual transmission of human papillomavirus, which causes

cervical cancer &anal cancer.

•  Men with cancer are twice as likely as women to have a

modifiable risk factor .[11]

•  lifestyle and environmental factors known to affect

cancer risk .

•  use of exogenous hormones (e.g.,

hormone replacement therapy causes breast cancer)

•  exposure to ionizing radiation and ultraviolet radiation,

and certain occupational and chemical exposures.

•  Every year, at least 200,000 people die worldwide from

cancer related to their workplace.[12]

•  Millions of workers run the risk of developing cancers

such as pleural and peritoneal mesothelioma from

inhaling asbestos fibers, or leukemia from exposure to

benzene .[12]

•  It is estimated that approximately 20,000 cancer deaths

and 40,000 new cases of cancer each year in the U.S. are

attributable to occupation.[13]

•  The Saudi Cancer Registry (SCR) of Saudi Arabia is

a population-based registry established in 1992

under the the Ministry of Health (MOH) by the

order of His Excellency the Minister of Health.

•  The SCR commenced reporting cancer cases from

01 January 1994.

Objec'ves:  

•  The primary goal of the SCR is to define the

population-based incidence of cancer in Saudi

Arabia. Additional objectives include programs

for early detection and cancer screening, as well

as cancer research projects.

Saudi Cancer Registry has eleven reports .

§  1994 Summary Report,

§  1994-1996 Incidence Report,

§  1997-1998 Incidence Report,

§  1999-2000 Incidence Report,

§  2001 Incidence Report,

§  2002, 2003, 2004, 2005, 2006,

§  2007and Incidence Reports.  

Cancer report Total reporting cancer cases

Estimated population at

K S A

Absolute incidence

1994-­‐1996   23092   14089156   54.36      per  1000000  

1997-­‐1998   14529   15121791   48.03      per  1000000  

1999-­‐2000   14856   15588805   47.06    per  1000000  

2001   5616   16056470   34.72    per  1000000  

2002   5876   15612781   37.63    per  1000000  

2003   8840   16109198   54.78    per  1000000  

2004   9381   16527340   56.76  per  1000000  

2005   10513   16945484   62.47  per  1000000  

2006   11040   17270181   63.92  per  1000000  

2007   12,309   17493364   70.63  per  1000000  

20  

25  

30  

35  

40  

45  

50  

55  

60  

65  

70  

75  

20  

25  

30  

35  

40  

45  

50  

55  

60  

65  

70  

75  Absolute  incidence    

absolute  incidence    

94   95   96   97   98   99   20   01   02   03   04   05   06   07  

Thyroid  C  73  

5.5   5.3   4.6   5   5.7   5.4   4.8   4.6   4.7   6.1   5.7   6.4   6.5   6.6  

Colon    C18   2.2   2.7   2.6   2.2   2.2   2.9   2.6   3.4   3.1   4.2   4.3   4.3   5.3   4.8  

NHL  C82,85,96   4.3   4.2   4.1   4   5   4.3   4.1   4.4   4.4   5   5   5.3   4.8   5.1  

94   95   96   97   98   99   20   01   02   03   04   05   06   07  

Leukemia  C92,94   1.8   1.8   1.7   1.6   1.7   1.6   1.7   1.8   1.8   1.6   1.9   1.6   2   1.5  

 Hodgkin  C81   1.4   1.3   1   1.1   1.3   1.2   1.2   1.1   1   1.5   1.4   1.3   1.6   1.6  

 stomach  C16   2.4   2.4   2.1   1.8   2   1.9   1.6   1.7   1.8   1.8   1.7   1.7   2.7   2.5  

 liver  C22  

3.9   3.1   3.3   2.9   3.8   2.7   3.2   2.7   2.8   3.3   2.9   3.1   3.1   2.6  

94   95   96   97   98   99   20   01   02   03   04   05   06   07  

Breast  C50  

13.4   13   13.4   13.3   14.3   12.6   13.7   12.1   13.9   14.6   16.5   18.7   18.1   21.6  

Corpus  uteri  C54  

2.1   1.4   1.4   1.6   2   1.6   2.5   2.1   2.2   2.8   2.9   3.6   3.6   4  

Corpus  cervix  C53  

2.4   2.2   2.5   2.3   2.9   2   1.9   2   1.8   1.9   2   2.1   1.6   1.9  

Ovary  C56  

2.9   3   2.7   3.1   3.1   2.2   2.2   2.4   2.3   2.5   2.4   2.9   3   2.6  

§  The total number of cancer incident cases reported to

the SCR was 12,309.

§  Overall cancer was slightly more among women than

men.

§  Cancers affected 5,982 (48.6%) males and 6,321

(51.4%) females with a male to female ratio of 95:100.

§  9,347 cases were reported among Saudis,

§  2,590 among Non-Saudis.

•  11,651 cases were analyzed, of which 9,124 (78.3%) were Saudis and 2,527 (21.7%) were Non-Saudis.

Among the Saudis •  4,351 (47.7%) were male •  4,773 (52.3%) were female. •  The male to female ratio

•  was 91:100. 47%  

53%  

proportion

Males  

Female  

Confirmation of Diagnosis of malignancy

•  Histologically in 86.2% of the cases.

•  Haematological & cytologically in 8% of cases.

•  Clinically confirmed cases were 0.3%.

•  Radiologically confirmed cases were 2%.

•  Cases confirmed by Death Certificate Only were

2.7% .

•  The method of diagnosis was unknown for 0.8%

of the cases.

Age adjusted rate (ASR) of all cancers among Saudi Population

47  48  49  50  51  52  53  

total   Men   Women  

CIR  

CIR per 100,000

Total 52.3%

Men 49.4 %

women 51.5%

Age adjusted rate (ASR) of all cancers among Saudi Population

77  78  79  80  81  82  83  84  85  

Total   Men   Women  

ASR  

ASR per 100,000  

Total 82.1

Men 80

women 84.2

The age-specific incidence rate (AIR) increased with

age for gender.

After the age of 64 years, the increase was nearly one and one half fold for males

compared to females.

The median age at diagnosis is was 59 years for men and

50 years for women

§  Riyadh Region 108.5/100,000

§  Tabuk Region 105.0/100,000 §  Eastern Region

104.4/100,000 §  Makkah Region

89.3/100,000 §  Madinah Region

73.8/100,000.  

0  

20  

40  

60  

80  

100  

120  

ASR  

ASR  

Percentage  distribu'on  of  most  frequent  type  of  cancer  by  gender  2007  age  (0-­‐14  year)Saudi  children    

Percentage  distribu'on  of  most  frequent  type  of  cancer  by  gender(  above  14  years)  2007  Saudi  Adult      

Percentage  distribu'on  of  most  frequent  type  of  cancer  by  age  and    gender  2007    

Percentage  distribu'on  of  most  frequent  type  of  cancer  by  gender  2007    

Percentage  distribu'on  of  most  frequent  type  of  cancer  by  gender  2007  age  (15-­‐29  year)  

Percentage  distribu'on  of  most  frequent  type  of  cancer  by  gender  2007  age  (30-­‐44  year)  

Percentage  distribu'on  of  most  frequent  type  of  cancer  by  gender  2007  age  (45-­‐59  year)  

Percentage  distribu'on  of  most  frequent  type  of  cancer  by  gender  2007  age  (60-­‐74  year)  

Percentage  distribu'on  of  most  frequent  type  of  cancer  by  gender  2007  age  (75+year)  

Males    

Females    

Specific cancer common in female

Males and 6.6 / 100,000 females

Preventive oncology

Summary Of Primary Preventive Actions

Prospects seem bright for ultimately preventing many

cancers. There is already much that can be done:

1. Quit smoking and use of tobacco in any from, and

encourage all nonusers not to start (especially the young).

2. Stop alcohol.

3. Control exposures to known carcinogens in the

workplace.

4. Reduce exposures outside the workplace to known

carcinogens such as arsenic, chromium, nickel, vinyl

chloride, and asbestos.

5.  Restrict use of drugs that are known/suspected to be

carcinogenic.

6. Prudent use of diagnostic x-rays.

7. Avoid excess exposure to sunlight, especially for fair

skinned persons, and encourage use of protective

creams and sunscreen.

8. Avoid giving estrogens to pregnant women. Use the

lowest dose necessary and include a progestin in the

regimen.

Summary Of Primary Preventive Actions

5.  Restrict use of drugs that are known/suspected to be

carcinogenic.

6. Prudent use of diagnostic x-rays.

7. Avoid excess exposure to sunlight, especially for fair

skinned persons, and encourage use of protective

creams and sunscreen.

8. Avoid giving estrogens to pregnant women. Use the

lowest dose necessary and include a progestin in the

regimen.

Summary Of Primary Preventive Actions

Screening for cancer

SCREENING AND 2 RY PREVENTION

•  By means of early detection followed by

definitive treatment.

•  Screening is one component of early

detection Secondary prevention can be

achieved only if there is a stage of that

cancer that is amenable to cure, and if

there are means of detecting the cancer

at that stage.

Natural history of a disease over time, including the pre-clinical stage in which a screening test can detect the

presence of disease.

A screening test can identify diseased individuals before Detection by routine diagnosis (Occurance of symptoms).

Treatment at the time of detection by screening, as opposed to the time of routine diagnosis, results in an improved chance of survival.

Biologic onset of disease

Disease detectable by screening

Detection by Screening test

Detectable by routine methods

Death

treatment

The clinical decision-making is based on probability.

Probability of breast cancer (percent)

0 20 40 60 80 100

Before mammogram

After positive mammogram

After positive FNA results

0.3 13 64

Diagnostic test (screening test) is to move the estimated probability of the presence of a disease toward either end of probability scale, thereby providing information that will alter subsequent diagnostic or treatment plans.

Bias in Screening lead-time bias    

DN

A d

amage

Can

cer begins

Can

cer first screen

detectable

Lead time

Death

Patient diagnosed from clinical symptoms

Apparent survival

Apparent survival Patient diagnosed by screening

Lead time

Lead time bias is an increase in survival as measured From detection of disease to death, without lengthening of life.

Advanced Uses of Screening Tests

-To Determine the probability that a disease is present’

-To assess the severity of an illness’ -To predict the disease outcome’ -To monitor response to therapy’ -To estimate the probability of an outcome.

Evaluation of a screening Test.

Evaluation of a Diagnostic Test.

Truth (gold standard) Test results (Screening

test)

No disease Disease

b False-positive

Non diseased+ positive test

a True positive

Disease present +test positive

Positive

d True negative Non diseased with

negative test

c False-

negative Have the disease

with negative test results

Negative

Evaluation of a Diagnostic Test. Sensitivity and Specificity

Sensitivity and specificity are descriptors of

the accuracy of a test.

The sensitivity of a test is defined as the percentage of persons with the disease of interest who have positive test results: few false positive

Sensitivity = X 100 = a/a + c X100 = 14/14+1 X100 = 93 %

True positives

True positive+ false negatives

Evaluation of a Diagnostic Test. Sensitivity and Specificity

Specificity of a test is defined as the percentage of persons without the disease of interest who have negative test results

It is the ability of the test to rule out the non-diseased few false negative

Specificity = X 100 = d /d + b X 100 = 91/91+8 X100 = 92 %

True negatives

True negatives + false-positives

Evaluation of a Diagnostic Test.

Total

Surgical biopsy FNA results

No cancer Cancer 22 8

False-positive

14 True

positive

Positive

92 91 True

negative

1 False-

negative

Negative

114 99 15 Total

Sensitivity = 14/14+1 X100 = 93 %

Specificity = 91/91+8 X100

= 92 %

Positive and Negative Predictive Value

Two measures concerning the estimation of the probability of the presence or absence of disease are the positive predictive value (PV+) and the negative predictive value (PV-).

The PV+ is defined as the percentage of who actually have the disease of interest to persons with positive test results (allow us to estimate how likely it is the disease of interest is present if the test is positive).

PV+= X 100 = a/a + b X100 = 14/ 14+8 X100 = 64 %

True positives

True positives +false positives

Positive and Negative Predictive Value

The PV- is defined as the percentage of who do not have the disease of interest to persons with negative test results :

PV- = X 100 = d/ d + c X100 = 91 /91+1 X100 = 99 %

True negatives

True negatives + false negatives

Likelihood Ratios (LR)

Likelihood Ratios LR + Likelihood Ratios LR -

Likelihood Ratios An LR+ of 1, indicates a test of no value in sorting

out persons with and without disease.

The larger the LR+more than 1 , the stronger the association between having a positive test result and having the disease.

LR+ of more than 10 is an indication of a test of high diagnostic value.

The smaller the LR- value, the better the diagnostic value of the test.

An LR- of 0.1 or less is an indication of a good diagnostic test.

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9.     

References  

References  9-­‐Saudi  cancer  register  incidence  report  ,2003.  

10-­‐Saudi  cancer  register  incidence  report,2004.  

11-­‐Saudi  cancer  register  incidence  report,2005.  

12-­‐Saudi  cancer  register  incidence  report,2006.  

13-­‐Saudi  cancer  register  incidence  report,2007.  14-­‐States  and  V.A.  at  Odds  on  Cancer  Data  (10  October  2007).  New  York  

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