Some Cancer Statistics

Cancer statistics are usually not based on an accurate count of cases but on estimations derived from various sources. There is no national cancer registry that counts every cancer diagnosed each year. The American Cancer Society publishes annual estimates based on a compilation of several local tumor registries and extrapolates these to the US population. Like all statistics, cancer numbers can be misused and misunderstood. For instance, the state of California made cancer a reportable disease in 1985, so they have reasonably good statistics. Marin county, an affluent ocean bordering county, has the highest incidence of breast cancer in the state, Fresno county, an inland agricultural county, one of the lowest.

Why is this? Maybe Marin county is deficient in agricultural chemicals in the environment and has too much fresh sea air. Are they too close to a nuclear power plant? Is there something in the water? Too much time spent in hot tubs and health food stores? Should you avoid Marin county? The explanation is not quite so exotic. The highest incidence of cancer occurs in older white women, women with fewer pregnancies, and those who have delayed their pregnancies. Marin county has a population of affluent older white women. Fresno county has a large population of young Hispanic multiparous women. Hispanics have a lower incidence of all cancers compared to white women.

Whenever you hear cancer statistics being quoted, beware. The numbers may be only estimates and will have been interpreted to support the point of view of whoever is quoting them. For example the incidence of breast cancer has increased over the past several years. Is there an epidemic of breast cancer? Most of this increase can be explained by the increased use of mammography screening. More early cancers are being found. If a magical new test were to become available today that could find a single cancer cell and if every woman had this test this year then there would be an enormous increase in the number of breast cancers diagnosed.

This increase would level off after several years, but there would be a huge increase for awhile; it would appear as though an epidemic were occurring. The most recent statistics show a leveling off and even a slight reduction in breast cancer in the USA. The increase in breast cancer over the last several years can easily be attributed to increased screening, as can the recent increase in prostate cancer.

Numbers don't lie, but what is inferred from them is almost always a distortion. For instance, what is the probability that the next time you fly someone will have brought a bomb onboard to blow up the plane? This can be estimated and will be a very small number. Assume that it is one in one hundred thousand flights (1:100,000). What is the probability that there will be two people with bombs on your flight? This will be an exceedingly small number, and is calculated by multiplying 1:100,000, by 1:100,000. This is 1:10,000,000,000. Conclusion: always bring your own bomb when you fly because the likelihood of there being two bombs is infinitesimal. So, provided you don't blow yourself up, there is an infinitesimal likelihood that anybody else on the plane will also have a bomb. The conclusion seems reasonable, but it is not. Do you know why the conclusion is mathematically erroneous?

LEADING CAUSES OF DEATH IN THE UNITED STATES
AMERICAN CANCER SOCIETY 1996

The leading cause of death for both men and women is heart disease and strokes. Forty percent of all deaths are due to the consequences of arteriosclerosis; 24 percent are due to cancers.

The life time risk of developing cancer for a man or woman is about 2 in 5. The risk of death from cancer is about 1 in 5. The risk of dying from heart disease and strokes is about 2 in 5.

THE AMERICAN CANCER SOCIETY
ANNUAL ESTIMATES

99,000 / 78,000

94,400 / 64,300

68,000 / 66,000

27,000 / 27,000

1,400 / 184,300

260 / 44,300

317,000 / 0

41,400 / 0

56,800 / 26,700

15,100 / 8,600

0 / 34,000

0 / 6,000

0 / 15,700

0 / 5,000

0 / 26,700

0 / 14,800

15,300 / 12,300

11,600 / 9,400

The most frequently diagnosed cancer in men is prostate cancer; in women it is breast cancer. The leading cause of deaths due to cancer in men is lung cancer; in women it is also lung cancer. More women die of ovarian cancer than from uterine and cervical cancer combined.

MORTALITY RATE PER 100,000 WOMEN UNITED STATES,
AMERICAN CANCER SOCIETY, 1996

The leading cause of cancer deaths for women used to be from cancer of the cervix, followed by cancer of the stomach. Both causes have decreased dramatically.

MORTALITY RATE PER 100,000 MEN UNITED STATES,
AMERICAN CANCER SOCIETY, 1996

Cancer of the breast had been the leading cause of cancer deaths in women for the past 40 years until recently when it was surpassed by lung cancer. The rate of increase in lung cancer deaths in women is beginning to look the same as the rate of increase in lung cancer deaths in men that began in 1940.

With the exception of lung cancer the death rates for almost all cancers have either decreased dramatically or remained stable for the past 60 years. There is some indication that most recently the death rates for breast cancer in women and lung cancer in men has peaked and is decreasing.

Men began dying of lung cancer in the 1940s because they started smoking in the 1920s. Women began smoking in the 1940s and 50s and began dying in the 1960s and 70s.

LEADING CAUSES OF DEATH FOR CHILDREN AGE 1-14, UNITED STATES,
AMERICAN CANCER SOCIETY

Cancer is the leading illness related cause of death in children. This is because there is not much else for them to die of. They don't get strokes, heart attacks, emphysema, complications from diabetes or other chronic diseases. There are only about 1,600 cancer deaths a year in children, but there are about 7,500 deaths due to accidents and trauma, which is the leading cause of death in children aged 1-14 years.

RISK OF BEING DIAGNOSED WITH AN INVASIVE CANCER FOR WOMEN
IN CALIFORNIA WITHIN THE NEXT 10,20,30 YEARS OR EVENTUALLY, BY AGE

Cancer became a reportable disease in California in 1985, so there are reasonably accurate statistics for the state. California has about one tenth of the US population with about the same distribution of cancers so you can extrapolate these numbers the US as a whole.

AVERAGE ANNUAL INVASIVE CANCER RATES PER 100,000 WOMEN,
BY RACE, IN CALIFORNIA

From above: if you are 45 years old the risk of developing a cancer within the next 10 years is 4.68%, within the next 30 years 24.57% and within your lifetime 41.09%. The risk of developing any cancer within the next year is low for every age group.

There are 363 cancers per 100,000 white women each year, but only 225 cancers per 100,000 Asian women each year. Even with age taken into account there are fewer cancers in Asians.

AVERAGE ANNUAL INCIDENCE (ACTUAL NUMBER) AND INCIDENCE
RATE (PER 100,000) OF INVASIVE BREAST CANCER IN WOMEN IN CALIFORNIA

The incidence of breast cancer per 100,000 women each year increases with age. The number of breast cancers that occur in the age group 40-49 years is almost the same as the number that occur in the age group 50-59 years. The rate is lower because there are more women in the younger age group. Nevertheless, mammographic screening should still be offered to these younger women just as it is for those in their fifties.

RISK OF BEING DIAGNOSED WITH INVASIVE BREAST CANCER
WITHIN THE NEXT 10, 20,30 YEARS OR EVENTUALLY FOR WOMEN IN CALIFORNIA

From above: if you are 65 years old the risk of developing breast cancer during the next 10 years is 4.47%. The risk is twice that of a woman 45 years old, but still 4.47% is a small number.

The tables cited above for California are part of a large compilation of data prepared by the Cancer Surveillance Section, Department of Health Services.

Perkins CI, Morris CR, Wright WE, and Young JL.
Cancer Incidence and Mortality in California by Detailed Race/Ethnicity, 1988-1992.
California Department of Health Services
Cancer Surveillance Section, April 1995.
Sacramento, Ca 94234-7320
tele: 916-327-4663

William M. Rich, M.D.
Clinical Professor of Obstetrics and Gynecology
University of California, San Francisco
Director of Gynecologic Oncology
University Medical Center
Fresno, California