Breast Cancer Probabilities

A National Cancer Institute (NCI) report estimates that about 1 in 8 women in the United States (approximately 13.3 percent) will develop breast cancer during her lifetime. This estimate is based on cancer rates from 1997 through 1999, as reported in NCI's Surveillance, Epidemiology, and End Results (SEER) Program publication SEER Cancer Statistics Review 19731999. This publication presents estimates of the risk of developing breast cancer in 10-, 20-, and 30-year intervals. Each age interval is assigned a weight in the calculations based on the proportion of the population living to that age.

The 1 in 8 figure means that, if current rates stay constant, a female born today has a 1 in 8 chance of being diagnosed with breast cancer sometime during her life. On the other hand, she has a 7 in 8 chance of never developing breast cancer. Because the SEER calculations are weighted they take into account that not all women live to older ages, when breast cancer risk becomes the greatest. A woman's chance of being diagnosed with breast cancer is:*

from age 30 to age 40 . . . . . . . 1 out of 252
from age 40 to age 50 . . . . . . . 1 out of 68
from age 50 to age 60 . . . . . . . 1 out of 35
from age 60 to age 70 . . . . . . . 1 out of 27
Ever . . . . . . . . . . . . . . . . . . . . 1 out of 8

In evaluating cancer risk for a cancer-free individual at a specific point in time, age-specific (conditional) probabilities are more appropriate than lifetime probabilities. For example, at age 50 a cancer-free black woman has about a 2.5-percent chance of developing breast cancer by age 60, and a cancer-free white woman has about a 2.9-percent chance.

Among the racial/ethnic groups studied by SEER**, non-Hispanic white, Hawaiian, and black women have the highest levels of breast cancer risk. Other Asian/Pacific Islander groups and Hispanic women have lower levels of risk. Some of the lowest levels of risk occur among Korean and Vietnamese women. These probabilities are based on population averages. An individual woman's breast cancer risk may be higher or lower depending upon a variety of factors; including family history, reproductive history and other factors that are not yet fully understood.

The NCI is directing special attention to women with disproportionately high rates of breast cancer and poor survival rates including members of certain minority groups and the medically under served. Efforts targeted at these groups are under way in all components of NCI's program: basic research, early detection, clinical trials, rehabilitation, education and information dissemination and cancer centers.

* Source: National Cancer Institute Surveillance, Epidemiology, and End Results Program, 19971999.

 ** Source: National Cancer Institute Surveillance, Epidemiology, and End Results Program, Racial/Ethnic Patterns of Cancer in the United States 19881992.

 Reprinted from

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Breast Cancer Probabilities