A 
Age Class / Age Group
In HKCaR, two types of age groups are generally used for cancer statistics:

A 
Agespecific Rate
The age specific rate (a_{i}, per 100,000 population) is a ratio of the event for the specific age group i. It is calculated by dividing the number of cases in the age class i (r_{i}) by the corresponding populationatrisk (n_{i}) and multiplying the result by 100,000. Thus,
a_{i} =
r_{i}
n_{i}
× 100,000

A 
Agestandardised Rate
Standardisation is necessary when comparing several populations with different age structures or for the same population over time in which the age profiles change accordingly. Comparisons with rates from other sources are valid only if they use the same standard population for calculations. The agestandardised rate (ASR, per 100,000 population) in accordance with direct method is calculated by summing up the products of the agespecific rates (a_{i}, where i denotes the i^{th} age class) and the number of persons (or weight) (w_{i}) in the same age subgroup i of the chosen reference Standard Population, then dividing the sum of Standard Population weights, i.e.
ASR =
Σa_{i}w_{i} Σw_{i} Cases of cancer of unknown age may be included in a series. An adjustment is made by multiplying the derived ASR by R Σr_{i} where R denotes the total number of cases; A denotes the number of age groups; Σr_{i} = r_{1} + r_{2} + r_{3} + ··· + r_{A}, where r_{i} denotes the number of cases occurred in the i^{th} age class; 
A 
Average Annual Percent Change
Average Annual Percent Change (AAPC)^{1} is a summary measure of the trend over a specified interval. It is computed as a weighted average of the annual percent changes over a period of years from the joinpoint regression model^{2}. HKCaR adopts at least the past 25 years of available data to estimate the AAPC of age standardised rate over the past ten years. In view of the data quality and sufficiency, except the figures published during 20092014, data from 1983 to 1990 are generally not included for estimation.
For details of calculation, please refer to the website of National Cancer Institute. References:

C 
Carcinoma insitu
Carcinoma insitu (Ca insitu) is noninvasive and the earliest form of cancer. Abnormal cells are present but have not spread to surrounding tissues or other parts of the body.
(Note: The cancer incidence and mortality published in the HKCaR website DO NOT include the cases of carcinoma insitu.) 
C 
Crude Rate
The crude rate (C, per 100,000 population) is the ratio of the number of people in which the event happens in a specific time period to the populationatrisk. It is calculated by dividing the total number of cases (R) by the total number of populationatrisk (N) and multiplying the result by 100,000 for common interpretation, i.e.
C =
R
N
× 100,000

C 
Cumulative Rate
The cumulative rate (CR%, unit: %) is the sum over each year of the agespecific incidence rates. It can be interpreted as an approximation of cumulative risk. The cumulative rate can be expressed as
CR% = 100 × Σa_{i}t_{i} CR%74 = 100 × Σ5a_{i} For illustration of the calculation, please refer to "Chapter 11 Statistical methods for registries, P.Boyle and D.M. Parkin, International Agency for Research on Cancer". 
C 
Cumulative Risk
The cumulative risk (or lifetime risk, unit: %) refers to the risk an individual would have of developing or dying from a particular cancer over his life span in the absence of any other cause of death. It can be expressed as
Cum. Risk = 100 × [1  exp ( CR% / 100)]

C 
Cytology
Cytology refers to diagnosis is determined by examining the cells under a microscope.

D 
DCO%
DCO%, one of the common quality indicators for assessing data completeness, is the percentage of cases which the information came from death certificate only.
A high DCO% implies high proportion of incomplete case ascertainment due to failure to capture cases while patients are alive. (See also MV%)

H 
Histology
Histology refers to diagnosis is determined by examining the histological characteristics of tissues or cells under a microscope, whilst the histology of a cancer refers to the microscopic characteristics of a tumour.

I 
International Classification of Diseases (ICD)
International Classification of Diseases (ICD) compiled by World Health Organization (WHO) is used to classify diseases and code diagnoses. In Hong Kong, ICD9 (the 9th Revision of ICD) and ICD10 (the 10th Revision of ICD) are commonly used to code malignant cancer cases. For the sake of consistency, those primarily based on ICD9 are converted to grouped ICD10 codes.

I 
International Classification of Diseases for Oncology (ICDO)
International Classification of Diseases for Oncology (ICDO) compiled by World Health Organization (WHO) is a dualaxial classification, with coding systems for both topography and morphology.
It is principally used in cancer registries and pathology reports.

I 
Incidence
Cancer incidence is the number of new cancer cases arising in a specified population over a given time period. It can be either expressed as an absolute number of cases per year or as a rate per 100,000 persons per year.

M 
Male : Female ratio
The sex ratio is the number of males for each female in a population.

M 
Median age
Median age is the age at the midpoint when the individuals are ranked by their age.

M 
Morphology
The morphology of a cancer refers to the histology and biological behavior of a tumour.

M 
Mortality
Cancer mortality is the number of cancer deaths occurring in a specified population over a given time period. It can be either expressed as an absolute number of deaths per year or as a rate per 100,000 persons per year.

M 
MortalitytoIncidence ratio
The MortalitytoIncidence ratio (MIR) serves as a populationbased indicator to evaluate disparities in cancer screening, incidence, treatment, and survival. It is defined as the agestandardised mortality rate divided by the agestandardised incidence rate. i.e.
MIR =
ASR_{mortality}
ASR_{incidence}

M 
MV%
Morphological verification refers to cases for which the diagnosis is based on histology or cytology. MV%, one of the common quality indicators for assessing data completeness, is the percentage of cases with a morphologically verified diagnosis. Higher the MV%, higher the accuracy of diagnosis. (See also DCO%)

P 
Populationatrisk (also known as personyears at risk)
Populationatrisk is the population that is exposed to the occurrence of an event (e.g. developing or dying from cancer) over a given time period. Generally, the population estimates are used to approximate the population at risk. The Hong Kong Cancer Registry adopts the midyear population estimates provided by the government's Census and Statistics Department for this quantity.

P 
Prevalence
The prevalence of cancer is an estimate of the number (or proportion of) the population alive on a specific date who had been diagnosed with cancer.
(Note: The HKCaR has yet to provide cancer prevalence in Hong Kong.) 
S 
Stage
Cancer staging provides information about the extent of disease spread, usually classified as Stage I to IV or Unstaged. The classification of staging is primarily based on the American Joint Committee on Cancer (AJCC) and Union for International Cancer Control (UICC) TNM staging system for most cancer sites. The HKCaR only records stage at diagnosis for invasive cancers.
In general, an overall stage of 0, I, II, III and IV can be assigned for most cancers according to the combination of T (describes the size of tumour), N (describes whether the tumour has invaded to the nearby lymph nodes) and M (describes whether the tumour has metastasized to other parts of the body):


S 
Standard Population
Standard population is the age distribution used as weights to create ageadjusted statistics. The most widely used has been the World Standard population modified by Doll et al., (1966) from that proposed by Segi (1960).
The sum of standard population weights (w_{i}, where i denotes the i^{th} age class) is 1, i.e.
Sum of weights =
Σw_{i} = 1 , where A = 18.
The table below shows various standard populations which have been used for ageadjusting in different countries. Distribution of World Standard Populations (in percent)


S 
Survival rate
Cancer survival rate is the proportion of patients alive at some point subsequent to the diagnosis of their cancer. It is represented as the probability of a group of patients "surviving" a specified amount of time (E.g. 3 years, 5 years or 10 years).

T 
Topography
Topography is the site in the body where the tumour is located.
