Breast Cancer Risk Factors

Question 1:
Does the woman have a medical history of any breast cancer or of ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS)?

Explanation
A medical history of ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS) increases the risk of developing invasive breast cancer. The method used by the Breast Cancer Risk Assessment Tool to calculate the risk of invasive breast cancer is not accurate for women with a history of DCIS or LCIS. In addition, the tool cannot accurately predict the risk of another breast cancer for women who have a medical history of breast cancer.

Question 2:
What is the woman's age?

Explanation
The risk of developing breast cancer increases with age. The great majority of breast cancer cases occur in women older than age 50. Most cancers develop slowly over time. For this reason, breast cancer is more common among older women.

Note: This tool only calculates risk for women 35 years of age or older.

Question 3:
What was the woman's age at time of her first menstrual period?

Explanation
Women who had their first menstrual period before age 12 have a slightly increased risk of breast cancer. The levels of the female hormone estrogen change with the menstrual cycle. Women who start menstruating at a very young age have a slight increase in breast cancer risk that may be linked to their longer lifetime exposure to estrogen.

Question 4:
What was the woman's age at her first live birth of a child?

Explanation
Risk depends on many factors, including age at first live birth and family history of breast cancer. The relationship of these two factors in white women is shown in the following table of relative risks.

Relative Risk of Developing Breast Cancer*

Age at first
live birth # of affected relatives
0 1 2 or more
20 or younger 1 2.6 6.8
20-24 1.2 2.7 5.8
25-29 or no child 1.5 2.8 4.9
30 or older 1.9 2.8 4.2

For women with 0 or 1 affected relative, risks increase with age at first live birth. For women with 2 or more first degree relatives, risks decrease with age at first live birth.

* Adapted from Table 1, Gail MH, Brinton LA, Byar DP, Corle DK, Green SB, Shairer C, Mulvihill JJ: Projecting individualized probabilities of developing breast cancer for white females who are being examined annually. J Natl Cancer Inst 81(24):1879-86, 1989. [PubMed Abstract]

Question 5:
How many of the woman's first-degree relatives - mother, sisters, daughters - have had breast cancer?

Explanation
Having one or more first-degree relatives (mother, sisters, daughters) who have had breast cancer increases a woman's chances of developing this disease.

Question 6:
Has the woman ever had a breast biopsy?
6a: How many previous breast biopsies (positive or negative) has the woman had?
6b: Has the woman had at least one breast biopsy with atypical hyperplasia?

Explanation
Women who have had breast biopsies have an increased risk of breast cancer, especially if their biopsy specimens showed atypical hyperplasia. Women who have a history of breast biopsies are at increased risk because of whatever breast changes prompted the biopsies. Breast biopsies themselves do not cause cancer.

Question 7:
If known, please indicate the woman's race/ethnicity.

Explanation
The original Breast Cancer Risk Assessment Tool was based on data from white women. But race/ethnicity can influence the calculation of breast cancer risk. The model for African American women was derived from the Women’s Contraceptive and Reproductive Experiences (CARE) Study (see reference 5) and NCI’s SEER Program. The model for Asian and Pacific Islander women in the United States was derived from the Asian American Breast Cancer Study (AABCS) and NCI’s SEER Program (see reference 6). For Hispanic women, part of the model is derived from white women who participated in the Breast Cancer Detection Demonstration Project and from SEER data. The risk estimates for Hispanic women are therefore subject to greater uncertainty than those for white women. Calculations for American Indian and Alaskan Native women are based entirely on data for white women and may not be accurate. Researchers are conducting additional studies, including studies with minority populations, to gather more data and to increase the accuracy of the tool for women in these populations.

Note: If the woman's race/ethnicity is unknown, the tool will use data for white females to estimate the predicted risk.

Question 7a:
What is the sub race/ethnicity?

Explanation
To calculate breast cancer risk using Asian-American as the race/ethnicity, the sub race/ethnicity needs to be known. If the sub-category of race/ethnicity is not known, then “Unknown” should be selected in Question 7, rather than Asian-American. The “Other Asian American” category includes women of Asian Indian/Pakistani, Korean, Vietnamese, Laotian, and Kampuchean descent. The “Other Pacific Islander” category includes women of Guamanian, Samoan, and Tongan descent.