[MOL] Learning the lingo..... [01469] Medicine On Line

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[MOL] Learning the lingo.....

Cancer Statistics

Cancer statistics are used for a variety of purposes. Researchers and =

cancer organizations (such as the National Cancer Institute) use =

statistics to track cancer trends. For example, if the incidence of any =

type cancer is seen to be increasing across several years, researchers =

will want to discover why and what can be done about it. Scientists also =

use statistics to determine how well a particular prevention or =

treatment method may be working: If a new chemotherapy drug increases =

the 5-year survival rate of patients with breast cancer, that shows =

scientists that the drug is a valuable addition to the treatment =


When it comes to the general public and cancer patients, the usefulness =

of cancer statistics depends on how they are interpreted and used. It =

has been widely reported that the lifetime risk of developing breast =

cancer is 1 in 8- a frightening thought for women who misinterpret that =

statistic to mean that at any time, they have a 1 in 8 chance of having =

breast cancer. The actual chances of developing breast cancer change =

throughout a woman's life, so that a 20-year-old woman has a current =

risk of only 1 in 2,500 of developing the disease within the next 10 =

years, and a 50-year-old woman has a current risk of about 1 in 39. =

Heredity, ethnicity, reproductive history, lifestyle factors and other =

risk factors all contribute to an individual's risk. So cancer =

statistics are useful when used for broad perspective but not for =

individual application.=20

The following definitions are provided to help you make sense of the =

sometimes confusing statistical terminology used when discussing cancer =

and its outcomes. Incidence describes the number of new cases of cancer =

developed by a specific population group within a set period of =

time-usually one year. For example, the total 2000 incidence of =

testicular cancer will be about 6,900 men. Incidence rate is the number =

of new cases in a population. The incidence is usually expressed in =

terms of the number of cases per 100,000 people. For example, the =

incidence rate for testicular cancer in the United States is =

approximately 3 new cases per 100,000 men, often stated simply as 3 per =


Prevalence is the total number of people with cancer or with a =

particular risk factor for cancer at a particular moment in time in the =

entire population. For large groups of people, prevalence is estimated =

by collecting information from a smaller subset of people and then =

extrapolating that information to the general population. For example, =

by collecting DNA information from breast cancer patients, scientists =

have estimated that the prevalence of the BRCA-1 gene in the total =

population is between 0.04 percent and 0.2 percent, meaning that much =

less than 1 percent of the total population has this breast cancer =

susceptibility gene.=20

Morbidity is a state of illness; i.e., it is often said that smoking is =

a major cause of morbidity in the U.S.=20

Mortality means pertaining to death.=20

Mortality rate is the number of people in a population group who die of =

cancer within a set period of time, usually one year. Cancer mortality =

rate is usually expressed in terms of deaths per 100,000 people. For =

example, the mortality rate for stomach cancer in the U.S. in 1930 was =

28 (28 deaths per 100,000 people), but dropped to 4 by 1992, meaning =

that only 4 people out of every 100,000 in the U.S. died of stomach =

cancer in 1992.=20

Prognosis is the prediction or estimation of the course and outcome of =

the disease, usually including the chances for recovery. While =

physicians may base a prognosis on statistical precedents, each =

individual is different, with actual outcomes affected by many factors, =

including the patient's age and general health, the type and stage of =

cancer, and the effectiveness of the particular treatment used. =

Therefore, while a prognosis may be helpful for explaining the =

seriousness of a disorder or for guiding treatment decisions, it cannot =

be used to predict disease outcomes for an individual.=20

Survival rate is the measure of the number of people who develop cancer =

and survive over a period of time. Scientists commonly use five-year =

survival as the standard statistical basis for defining when a cancer =

has been successfully treated.=20

The 5-year survival rate includes anyone who is living five years after =

a cancer diagnosis including those who are cured, those in remission, =

and those who still have cancer and are undergoing treatment. For =

example, when colorectal cancers are detected early, the 5-year survival =

rate is 92 percent, meaning that 92 percent of all colorectal cancer =

patients live at least 5 years after diagnosis if the cancer is detected =


The "overall" 5-year survival rates measure everyone who has ever been =

diagnosed with a particular cancer equally, which may lead to distorted =

statistics. For example, a 90-year-old man and a 30-year-old man who =

have the same cancer will be grouped together. The 90-year-old may die =

of other causes within the five-year period due to normal life =

expectancy, and this can skew the data. A more statistically accurate =

view of survival is the "relative" 5-year survival rate, which compares =

cancer patients' survival rate with the survival rate of the general =

population, taking into account differences in age, gender, race and =

other factors. In this case, the 30-year-old and the 90-year-old would =

be treated as statistically different.=20

Risk refers to the chance that an individual will contract a disease. =

High-risk is when the chance of developing cancer is greater than the =

chance for the general population. For example, people who smoke have a =

high risk of developing lung cancer compared with people who don't =


Risk factor is anything that has been identified as increasing a =

person's chance of getting a disease. These can be controllable or =

uncontrollable, personal or environmental. For example, risk factors for =

developing colon cancer include having a hereditary predisposition to =

the disease (uncontrollable) and eating a high-fat, low-fiber diet =


Relative risk is a measure of how much a particular risk factor =

increases the risk of development of a specific cancer. For example, the =

risk for developing ovarian cancer increases by 300 percent for a woman =

with a close family history of the disease compared to a woman without a =

family history. In this example, the relative risk of developing ovarian =

cancer is 3 for those with a family history, meaning they have 3 times =

the risk.=20

Attributable risk is a measure of how much of the total incidence of =

disease is caused by that risk factor. For example, even thought the =

relative risk of developing breast cancer for a woman with the BRCA-1 =

gene is high, since the prevalence I of the BRCA-1 gene is low, most =

cases of breast cancer are not caused by the BRCA-1 gene.=20

Lifetime risk is the probability of developing or dying of cancer =

sometime during one's lifetime. A person has a lifetime risk of 2 in 5 =

of developing cancer, meaning that for every five people in the =

population, two will eventually develop cancer. The lifetime risk of =

dying of cancer in 1 in 5.=20

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