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BASIC STATISTICAL PRINCIPLES (In relation to Cancer Registration)
BY
Dr. T. RamnathScientist F
National Cancer Registry Programme
(Indian Council of Medical Research)
Bangalore
DECEMBER -2012
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Few Important terms used in NCRP – Reports
1. Cancer 2. Cancer Registration
3. Cancer Registry 4. Registry Area
5. Population at risk 6. Crude rate
7. Age specific rate 8. Age adjusted rate
9. Leading sites
10.Graphical presentation of the data
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Cancer: Is a group of diseases characterized by the uncontrolled growth and spread of abnormal cells.
Cancer Registration: It is a continuous process of systematic collection of Data on the occurrence and characteristics of reportable neoplasms.
Continuous: Main feature that distinguishes cancer registration from a cancer survey – which is for a limited period of time.
Systematic: Implies collection of data from all cancer cases in a prescribed format from various sources in a given population.
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All neoplasms with a morphology behaviour
code of “3” as defined by the International
Classification of Diseases – Oncology, Third
Edition, are considered as Reportable
neoplasms.
- Excludes /0 benign tumors – adenoma,
fibroma.
- Excludes/1 uncertain whether benign or
malignant.
- Excludes / 2 carcinoma–in-situ.
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Cancer Registry: It is an organization or an office
for the systematic collection, storage, analysis,
interpretation and reporting of data on subjects
with cancer.
At present, there are 27 PBCRs and 9 HBCRs
which are functioning under the network of NCRP.
According to Cancer Incidence in Five Continents,
published by IARC, France, more than 440
registries from 81 countries are functioning in the
world.
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Registry Area: It is the well defined Geographical
area from which cancer cases are registered by
the Registries.
Population at risk: The population as a whole or a
part which is susceptible to have a specific cancer
is known as Population at risk. It is defined on the
basis of demographic data, such as place of
residence, sex, age group and ethnicity. It is the
population residing in the Registry area which is
at the risk of developing cancer.
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Incidence : It is the number of new cases arising
in a given period from a defined area.
1. Number of persons with certain disease
condition (cancer cases).
2. Period of time (one year/two years) and
3. Registry area or Place.
This information is collected routinely by Cancer
Registries and can be expressed as an absolute
number of cases per year.
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Example:
The PBCR of Bhopal has reported the registration of 3977 new cancer cases during the period 2006-08.
Incidence Rate: The incidence rate is simply
calculated by dividing the number of new cases
by the population at risk. For cancer, the
incidence is expressed as an annual rate per
100,000 population or person at risk.
1. Number (persons), 2. Area (place)
3. Period and 4. Population at risk
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Prevalence : Prevalence is the existing
number of cases (New + Old) observed in a
given period in a specified population. This
can be expressed as an absolute number of
cases per year.
Prevalence Rate: The Prevalence rate is
simply calculated by dividing the existing
number of cases by the population at risk.
For cancer, the Prevalence is expressed as
an annual rate per 100,000 population or
person at risk.
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Relationship between Incidence and
prevalence
The prevalence and incidence rates are related
in the following way:
Prevalence = Incidence * period
P = I*D
The prevalence (P) is proportional to the product
of the incidence rate (I) and the average duration
of the disease.
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For Chronic diseases
Incidence < Prevalence
For Acute diseases:
Incidence > Prevalence
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Definitions: New cancer cases during a year Crude rate = Estimated Population* of the same year X 100,000
Crude rate Average cancer cases during the given Period(Period) = Average of Populations** for the same period
X 100,000 * Mid year; ** Mid years
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Definitions:
Crude rate New cancer cases for the given Period(Period) = Estimated person years for the period
X 100,000
In Epidemiological or Cohort studies, relatively small
number of individuals are followed up and categorised
according to presence of absence of risk factors which are
responsible for development of certain disease condition(s)
among them.
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Invariably , there will be withdrawals of subjects from the
group under study owing to death, migration and inability
to trace them. Often new individuals are added up in the
study to maintain the requried number of subjects under
the study. The result is that individuals are under the
observations and at the risk of disease for varying length
of period. Thus, the denominator for calculation of
incidence rate is calculated by summing up the person
years which are contributed by them.
Person years:
It is the cumulative sum of time periods for which the
population is exposed to the risk of developing certain
disease condition during the specified period of time.
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Calculation of Person years for Incidence rate
SUBJECT 2001 2002 2003 2004 2005 2006 2007 Time at risk
A 2
B + 4
C + 4
D 5
E 5
Total years at risk 20
Incidence = 2 person for 20 person years
= 10 /100 person years of observation
Hypothetical group of 5 persons with certain risk factor were followed up for 7 years, two of whom developed the disease of interest.
Here, we are dealing with the time for which the population is exposed.
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Registry Area
Cases
Bangalore 2665
Kolkata 2134
Chennai 2375
Mumbai 5356
Population
3552676
2529719
2354949
7336175
Crude Rate
75.0
84.4
100.9
73.0
No. of Cancer Cases by Registry Area and Crude Rate - Males - 2006
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Registry Area Crude Rate
Dibrugarh District
74.3
Aizawl District
150.8
Imphal East 43.4
Imphal West 87.6
Population
13,11,765
3,84,711
4,35,619
4,83,151
Cases
975
580
189
423
No. of Cancer Cases by Registry Area and Crude Rate - Males - 2006
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2006 2007 2008
No. of Cases 2375 2499 2518 7392
Estimated Population
23,54,949 23,81,244 24,07,832 71,44,025
Crude Rate per 100,000
100.9 104.9 104.6 103.5
Calculation of Crude Rate and Average Crude Rate - All Sites - Chennai - Males - (2006-08)
Variable PooledReporting Year
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Definitions: New cancer cases during a year Age specific for a particular age group Rate = X 100,000 Estimated Population* of the same year for the same age group
Average Average cancer cases during the given timeAge specific Period for a particular age group Rate = X 100,000 Average Population** of the same Period for the same age group
* - For mid year; ** Person Years
00 - 04 40 - 44
05 - 09 45 - 49
10 - 14 50 - 54
15 - 19 55 - 59
20 - 24 60 - 64
25 - 29 65 - 69
30 - 34 70 - 74
35 - 39 ≥ 75*
Age group (in years) considered for reporting purposes
75-79 80-84 ≥ 85 *
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Age group (years)
No. of cases
Population Age Sp. Rate
Age group
No. of cases
Population Age Sp. Rate
0 - 4 12 264199 4.5 40 - 44 136 227067 59.9
5 - 9 30 279257 10.7 45 - 49 198 204910 96.6
10 - 14 20 311089 6.4 50 - 54 290 155992 185.9
15 - 19 31 338451 9.2 55 - 59 287 96839 296.4
20 - 24 36 435358 8.3 60 - 64 362 82766 437.4
25 - 29 53 409191 13.0 65 - 69 341 53778 634.1
30 - 34 72 320236 22.5 70 - 74 310 40048 774.1
35 - 39 97 291160 33.3 > = 75 379 42335 895.2
1 Total 2655 3552676 74.7Age not known
Cancer cases and population by different age groups - All sites - Bangalore - Males – 2006
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Application of Age Specific Incidence and Mortality Rate of Bangalore PBCR to Populations of different Countries and
Change in CR – Males - 2006
Country PBCR Population* CR CMR
India Bangalore 3,133,069 73.3 28.6Canada - 14,534,508 140.1 59.6Finland - 2,490,658 151.7 64.2Australia South
731,707 153.3 66.3
USA Connecticut 1,405,295 160.3 70.0
China Hong Kong 3,348,040 161.2 68.2
UKEngland, Merseyside and Cheshire
1,170,326 165.8 71.8* Source: Five years break-up by Cancer Incidence in Five Continents - Vol. VIII - IARC Scientific Publication No.155 - 2002
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Percentage Age Distribution of different countries
PBCR AreaBroad Age group (years)
<25 25-44 45-64 65+
Bangalore 47.1 34.5 14.7 3.7
Canada 35.2 33.6 21.0 10.2
Finland 32.9 31.0 25.2 10.9
Australia- South 35.7 31.1 21.3 12.0
USA 32.9 33.0 21.4 12.7
UK -England, Merseyside and Cheshire
34.2 29.6 23.4 12.8
China- Hongkong 31.8 34.5 18.8 14.8
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2006 2007 2008
No. of Cases
92 81 74 247
Estimated Population
144117 147292 150510 441919
Crude Rate 63.8 55.0 49.2 55.9
Calculation of Average Age Specific Rate (AASR) - Breast Cancer - (40-44 years) - Chennai (2006 - 2008)
Variable Reporting Year
Pooled
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Age adjusted or Age standardized rate:
∑ aiwi AAR = for i = 1,2,….n ∑ wi Where
ai = Age specific rate for age group i
wi = the world standard population for age group i
n = the no. of age groups (n=16)
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Incident rate (per 100,000 population) of Cancer – All sites - Bangalore - Males – 2006 & World Standard Population
Age group
(years)
Incidence rate (ai )
World standard
population ( Wi )*
Age group
(years)
Incidence rate*(ai )
World standard
population ( Wi )*
0 - 4 4.5 12000 40 - 44 59.9 6000
5 - 9 10.7 10000 45 - 49 96.6 6000
10 - 14 6.4 9000 50 - 54 185.9 5000
15 - 19 9.2 9000 55 - 59 296.4 4000
20 - 24 8.3 8000 60 - 64 437.4 4000
25 - 29 13.0 8000 65 - 69 634.1 3000
30 - 34 22.5 6000 70 - 74 774.1 2000
35 - 39 33.3 6000 > = 75 895.2 2000
All ages 74.7 100000
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Age group (years)
aiwiAge group aiwi
0 - 4 54504 40 - 44 359365 10851328/100000
5 - 9 107428 45 - 49 579767 108.5
10 - 14 57861 50 - 54 929535 5003540/31000
15 - 19 82434 55 - 59 1185473 161.4
20 - 24 66152 60 - 64 1749511 8453948/36000
25 - 29 103619 65 - 69 1902265 234.8
30 - 34 134901 70 - 74 1548142
35 - 39 199890 > = 75 1790481
TR(35-74) =
Age specific rates and World Standard Population by different age groups - All sites - Bangalore - Males – 2006
AAR =
TR (35-64) =
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No. of sites for which cases and incidence rates are reported:
Males: 51 sites (C00- C95)
Lip, Tongue, Mouth, Salivary glands, Tonsils, ..... Hypopharynx, Oesophagus, stomach...... Larynx, lung ..... Prostate. Testis,... Kidney, Eye, .... Myelomas,, Leukaemias
Females: 55 sites (C00-C95)
Lip, tongue, mouth, salivary glands, tonsils, ..... Hypopharynx, Oesophagus, Stomach ..... Larynx, Lung ..... Breast, Cervix, Ovary, ... Kidney, Eye, .... Myelomas, Leukaemias
Common sites: C00-C47+C49; C64-C95 (29 sites) (18 sites)Male genital organs: C60-C64 (4 sites)Female genital organs: C50-C58 (8 sites)
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Ten leading sites of Cancer - Bhopal - Males - (2006-08)
Sl. No. Leading SitesNo. of cases
%
1 Lung 207 10.3
2 Mouth 205 10.2
3 Tongue 195 9.7
4 Oesophagus 107 5.3
5 Larynx 98 4.9
6 Hypopharynx 92 4.6
7 NHL 88 4.4
8 Prostate 82 4.1
9 Brain NS 55 2.7
10 Stomach 50 2.5
All Sites 2015 100.0
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Crude Mortality Rate Cancer deaths during a year = X 100,000 Estimated Population* of the same year
Age specific Mortality Rate
Cancer Deaths during a year for a particular age group = X 100,000 Estimated Population* of the same year for the same age group
* - For mid year
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Age group (years)
No. of cases
Population
Age Sp. Rate
Age group
No. of cases
Population
Age Sp. Rate
0 - 4 6 264199 2.3 40 - 44 37 227067 16.35 - 9 5 279257 1.8 45 - 49 55 204910 26.8
10 - 14 4 311089 1.3 50 - 54 115 155992 73.715 - 19 5 338451 1.5 55 - 59 112 96830 115.720 - 24 8 435358 1.8 60 - 64 128 82766 154.725 - 29 12 409191 2.9 65 - 69 152 53778 282.630 - 34 15 320236 4.7 70 - 74 155 40048 387.035 - 39 27 291160 9.3 > = 75 199 42335 470.1
3 Total 1038 3552676 29.2
Cancer mortality cases and mortality Incidence rates by different age groups - All sites - Bangalore - Males – 2006
Age not known
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Registry C.R. A.A.R.
Bangalore 78.2 113.4
Barshi 47.3 51.5
Bhopal 70.4 104.6
Chennai 103.5 115.2
Delhi 75.5 124.3
Mumbai 70.2 99.1
Crude Rate (C.R.), Age Adjusted Rate (A.A.R.) per 100000 Population by different Registries -
(2006-08)
Source: NCRP Report – (2006-08)
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Registries Relative %
Microscopic 80.3
X-Ray 2.5
Clinical 10.7
Others 1.4
DCO 5.1
Total 2015
Percentage Distribution of Cancer Cases according to different Methods of
Diagnosis - Bhopal - Males - 2006-08
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PBCRs - 27HBCRs – 9POCSS - 17
NATIONAL CANCER REGISTRY PROGRAMME, BANGALOREIndian Council of Medical Research
List of PBCRs
1. Tata Memorial Hospital, Mumbai;2. Kidwai Memorial Institute of Oncology,
Bangalore;3. Cancer Institute (WIA), Adyar, Chennai4. Regional Cancer Centre, Thiruvananthapuram5. Assam Medical College, Dibrugarh6. Postgraduate Institute of Medical Education &
Research, chandigarh7. Dr. B. Borooah Cancer Institute, Guwahati8. Government Medical College, Bhopal9. All Indian Institute of Medical Sciences, New
Delhi
NATIONAL CANCER REGISTRY PROGRAMME, BANGALORE
Indian Council of Medical Research
List of HBCRs