Many women may be familiar with the statistic, one in eight wome Study Finds Risk of Breast Cancer Misinterpreted by Many Women (dateline April 10, 2001) | Breast Health News | Imaginis - The Women's Health & Wellness Resource Network

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Study Finds Risk of Breast Cancer Misinterpreted by Many Women (dateline April 10, 2001)

Many women may be familiar with the statistic, "one in eight women will develop breast cancer." However, a new study reports that this lifetime risk if often misinterpreted, causing many women to overestimate their chances of developing breast cancer. Instead, the researchers believe that risk projections over a shorter period of time, with specific attention to age and race/ethnicity, may be more helpful for each woman in understanding her breast cancer risk.

The often-cited "one-in-eight" statistic means that for a female who is born today and lives to be 85 years of age, her lifetime risk of developing breast cancer is one in eight (or approximately 12.8%). This statistic is based on population averages. Each woman's breast cancer risk may be higher or lower, depending upon a several factors, including family history, genetics, age at first menstruation, and other factors that have not yet been identified. Also, the "one-in-eight" statistic does not take into account specific age groups or races, which may influence breast cancer risk.

In an effort to clarify the overall risk of breast cancer, Dr. Cyllene R. Morris and her colleagues from the Public Health Institute in Sacramento, California estimated the risk of developing breast cancer within the next five, 10, or 20 years for women of four major races/ethnic groups currently between the ages of 30 and 70. Data were collected from the California Cancer Registry and statewide mortality rates, and the results of the study were published in the April 2001 issue of the American Journal of Preventive Medicine.

The results of the study revealed that for women currently aged 30, there is a 2% (1 in 50) chance that they will develop breast cancer within the next 20 years. When women reach 40 years of age, the overall risk increases to 4.3% (1 in 20), based on an increase in age.

When taking into account specific races/ethnic groups, the researchers found that among women currently aged 50, the estimated risk of developing invasive breast cancer within 5 years ranged from 0.8% (1 in 133) among Hispanics to 1.3% (1 in 75) among Caucasians. Invasive breast cancer (as opposed to non-invasive breast cancers such as ductal carcinoma in situ) describes cancer that has spread past the ducts and lobes to invade surrounding fatty and connective tissues of the breast.

For women aged 50, the risk of developing breast cancer within 10 years is 2.9% (1 in 34) among Caucasians, 2.3% (1 in 43) among African Americans, 2.0% (1 in 51) among Asian/Pacific Islanders, and 1.6% (1 in 63) among Hispanics. The risk of developing breast cancer within 20 years increases among all races/ethnic groups for women currently aged 50. The following table summarizes the team’s data for women currently aged 50.

Estimated Risk of Developing Invasive Breast Cancer

Age/Race Risk Within 10 Years Risk Within 20 Years
50 years old,
1.6% (1 in 63) 3.7% (1 in 27)
50 years old,
Asian/Pacific Islander
2.0% (1 in 51) 3.9% (1 in 26)
50 years old,
2.3% (1 in 43) 5.0% (1 in 20)
50 years old,
2.9% (1 in 34) 6.6% (1 in 15)

By estimating breast cancer risk within the next one or two decades based on age and race/ethnicity, Dr. Morris and her colleagues believe that women will be less likely to overestimate their risk of breast cancer. According to the National Cancer Institute, on average, Caucasians and African-Americans have the highest levels of breast cancer risk while Asian/Pacific Islanders and Hispanic women have a lower risk of developing breast cancer (less than two-thirds that of Caucasian women). Koreans, Native Americans, and Vietnamese women have the lowest risk of breast cancer.

While the risk of breast cancer increases as women age, several other factors have been identified that put women at a higher-than-average risk of breast cancer. These factors include:

  • Family or personal history of breast cancer
  • Genetics (specifically mutations of the BRCA1 or BRCA2 genes)
  • Previous breast biopsies showing non-cancerous conditions (such as LCIS or atypical hyperplasia)
  • Early onset of menstruation (before age 12) or late menopause (after age 50)
  • Having a first child after age 30 or never having children
  • Alcohol/smoking and diet/obesity
  • Previous radiation therapy (especially during childhood)
  • Long-term use of hormone replacement therapy (more than five years)

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