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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