1. By
Basem Salama Eldeek
MSc,MD,MHPE
Associate prof of community medicine
Faculty of medicine king Abdulaziz university,KSA
And mansoura university ,Egypt.

2. Acknowledgement

4. • 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.

5. • This area of study must contend with
problems of
• lead time bias
• length time bias.

6.
• 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.

7. • 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
implementation of screening programs.

8. • 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.

9.
• 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.

10. 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.

11.
• 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.

12.
• 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]

14. • 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.

15. 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.

17. 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.

18. 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

19. 20
25
30
35
40
45
50
55
60
65
70
75

20. 20
25
30
35
40
45
50
55
60
65
70
75
Absolute
incidence
absolute
incidence

21. 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

22. 94
95
96
97
98
99
20
01
02
03
04
05
06
07
Leukemi
a
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

23. 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

24. § 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.

25. • 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

26. 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.

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

28. 47
48
49
50
51
52
53
total
Men
Women
CIR
CIR per
100,000
Total 52.3%
Men 49.4 %
women 51.5%

29. 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

30. 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

31. § 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

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

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

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

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

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

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

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

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

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

44. Males

45. Females

46. Specific cancer common in female

63. Males and 6.6 / 100,000 females

83. Preventive oncology

84. 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.

85. 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

86. 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

87. Screening for cancer

88. 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.

89. 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

90. 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.

91. Bias in Screening
lead-time bias
DNAdamage
Cancerbegins
Cancer
firstscreendetectable
Lead
time
Death
Patient diagnosed from clinical symptoms
Apparent survival
Apparent survivalPatient 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.

92. 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.

93. Evaluation of a screening Test.

94. Evaluation of a Diagnostic Test.
Truth (gold standard)
Test results
(Screening
test)
No diseaseDisease
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

95. 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

96. 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

97. Evaluation of a Diagnostic Test.
Total
Surgical biopsy
FNA results
No cancerCancer
228
False-
positive
14
True
positive
Positive
9291
True
negative
1
False-
negative
Negative
1149915Total
Sensitivity =
14/14+1 X100
= 93 %
Specificity =
91/91+8 X100
= 92 %

98. 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

99. 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

100. Likelihood Ratios
(LR)
Likelihood Ratios LR + Likelihood Ratios LR -

101. 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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