Cancer Incidence Related Definitions and Associated Formulas
This link shows formulas used to calculate rates with examples.
Mortality - The number of deaths, with a certain type of cancer
as the underlying cause of death, during a specific time period (i.e. one year).
Cancer mortality is usually expressed as the number of deaths due to cancer per
Frequency - The number of deaths from a certain type of cancer
during a specific time period.
Rate - The number of deaths from a certain type of cancer divided by the population
of individuals in that geographic area (i.e. state, county) during a specific time.
Crude Rate - The number of deaths during a specific time period
and in a specific geographic area per 100,000 individuals who are susceptible to
Age-specific rate - The number of deaths from a certain type of
cancer per 100,000 individuals over a specific time period for a specific age group.
Age-adjusted rate - Cancer rates vary with age, and populations
vary by their age distributions. Age adjustment allows for comparison of rates between
different populations with different age structure. The "effect of age"
is no longer present upon age-adjustment. Age-adjusted rates are calculated using
the age distribution of the 1970 or 2000 US standard population, and they are usually
expressed per 100,000 population.
95% Confidence Intervals - The formulas used to calculate the 95%
confidence intervals is R + 619.81*(R/D)1/2
Where R = crude cancer mortality rate, D = population denominator, and 619.81=1.96*(100,000)1/2
When frequencies are less than 100 then 95% confidence intervals are calculated
using the formulas provided on pages 98-102 in the
NCHS 2001 Birth Report a pdf document.
Rate Calculations With Small Numbers - There are variations in
all statistics that are the result of chance. This characteristic is of particular
importance in classifications with small numbers of events where small variations
are proportionately large in relation to the base figure. As an example, small changes
in the number of deaths in small population areas or in the number of deaths from
a rare cancer could result in large changes in these crude rates. For this reason,
rates for counties with small populations or other small bases should be used cautiously.
Race - Race is reported as White, Black, Other, and Unknown. Other
race group includes Asian, Pacific Islander, and Native Americans.
Age - Age at death
Population Data - With the exception of population data by race
and population data for selected age groups of teens, the 2000 Census data, provided
by the Office of Research and Statistics (South Carolina Budget and Control Board),
were used to calculate the rates in this report. Population data by race and for
selected age groups were modified. Age Adjusted rates use 18 age groups and the
corresponding 18 standard weights from the 1970 and 2000 U.S. population.
Population Data By Race - The U.S. Census Bureau Population data
contains data for both "multiple race", and single race categories. This
presents problems for calculating vital statistical rates. The following methodology
was developed jointly by Office of Research and Statistics, South Carolina State
Budget and Control Board and the Division of Biostatistics and Health GIS, Public
Health Statistics and Information Services, SCDHEC.
The populations of these two race categories were allocated to the standard single
race categories by age, gender and county. This allocation was based on the proportional
distribution of the population of the standard single race categories within each
of these age, gender, county groups.
Population Data For Selected Age Groups - For inter-census years,
ORS provides estimated population data for South Carolina by age for five-year age
groups. It is assumed that the population within each of these age categories is
distributed uniformly through out the age interval. Based on this assumption, the
population for females 14-17, 15-17 and 18-19 years is derived, consecutively, as
follows - (20% of the female population 10-14 years plus 60% of the female population
15-19 years), (60% of the female population 15-19), and (40% of the female population
Residence Data - Data allocated to the place in South Carolina
where the person lived at time of death.
SOURCES OF INFORMATION
Centers for Disease Control (CDC) - Located in Atlanta, GA, the
CDC is an agency of the Department of Health and Human Services. The CDC serves
as the national focus for developing and applying disease prevention and control,
environmental health, and health promotion and education activities designed to
improve the health of people of the United States.
National Program of Cancer Registries (NPCR) - Funded by the CDC,
the NPCR is a population-based system of cancer registries established in 1992 by
the Central Cancer Registries Amendment Act (Public Law 102-515). When fully implemented,
programs funded by the NPCR will collect data on cancer for 96% of the US population.
Surveillance, Epidemiology and End Results (SEER) - Program of
the National Cancer Institute that collects and publishes cancer incidence and survival
data from 11 population-based cancer registries and three supplemental registries
covering approximately 14 percent of the United States population.
Cancer site - The body organ or system where cancer originates;
the anatomical site of origin.
Metastasis - Movement of disease from one organ or part to another
not directly connected.
Risk factor - Anything that increases a person's chances of getting
a disease. Examples include smoking, diet, and age.
Cancer cluster - A group of more cancer cases/deaths than normal
in a small area, like a neighborhood, or within a short time period. Cancer clusters
are reported when people learn that an unusual number of their friends, family,
neighbors or co-workers have cancer.
COUNTIES BY REGIONS
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