| Breast cancer is the most common cancer and the | | | | altered BRCA1 or BRCA2 gene. In other words, |
| second leading cause of cancer deaths in women in | | | | women with an altered BRCA1 and/or BRCA2 gene |
| the United States. In 2008, approximately 184,450 | | | | are up to eight times more likely to develop breast |
| patients were estimated to be diagnosed with | | | | cancer than women without alterations in those |
| invasive breast cancer, and an estimated 40,930 | | | | genes. The BRCA1 mutation confers a higher risk |
| were estimated to die of this disease. | | | | than a BRCA2 mutation. Women who inherit a |
| Furthermore, over 50,000 female carcinoma in situ | | | | damaged BRCA1 gene have a 60-85% chance of |
| breast cases would have been diagnosed. The | | | | developing breast cancer at some stage in their lives |
| etiology of breast cancer is poorly understood with | | | | and a 20-40% chance of developing ovarian cancer. |
| multiple genetic and environmental factors involved in | | | | For BRCA2, the risks are 40-60% and 10-20%, |
| the initiation and progression of cancer. | | | | respectively. |
| | | | | |
| Scandinavian Twin Study: For years, there has been | | | | Family History and Breast Cancer: Although the |
| a hot debate as to whether the cause of breast | | | | spotlight in hereditary breast cancer has been |
| cancer is genetic or environmental. Then in 2000, | | | | directed on the BRCA genes, the majority of |
| Lichtenstein and his colleagues at the Karolinska | | | | patients with a family history of breast cancer are |
| Institute in Sweden published their study of 44,788 | | | | BRCA1 and BRCA2 negative. Even in these BRCA |
| pairs of twins from the Swedish, Danish, and Finnish | | | | negative patients, however, there is an increased risk |
| twin registries. In this study, they looked at cancer | | | | of developing cancer with a family history of breast |
| risk with 28 different types of cancers and did | | | | cancer. Six factors (unrelated to BRCA genes) |
| statistical modeling of genetic and hereditary | | | | have been studied in patients with a family history of |
| contributions in eleven different cancer types. For | | | | breast cancer. They are as follows: |
| breast cancer, they clearly showed that only 27% of | | | | |
| breast cancers were due to genetic factors. This | | | | 1. Degree of relationship: If the family member |
| was an even lower hereditary component than other | | | | with a history of cancer is a first degree relative, the |
| common cancers such as prostate and colorectal. | | | | increased risk is much greater than for second |
| This study and others have confirmed the fact that | | | | degree relatives. |
| over 70% of breast cancers are influenced by | | | | 2. Number of relatives who have had breast |
| environmental factors. | | | | cancer: People with two or more family members |
| | | | | who have had breast cancer are at higher risk than |
| BRCA genes: Although much attention has been | | | | those with only one affected relative. |
| made about hereditary breast cancer, only two | | | | 3. Age of onset of cancer: If the relative |
| genes are commonly tested for breast cancer risk | | | | developed breast cancer at an early age |
| assessment. These two genes are tumor | | | | (pre-menopausal), the risk is higher than if the relative |
| suppressor genes named "BRCA1" and "BRCA2" that | | | | developed post menopausal breast cancer. |
| are involved with DNA repair. These two genes | | | | 4. Bilateral breast cancer: If the relative has a |
| only account for about 5% of all breast cancers. | | | | history of bilateral breast cancer, the risk is greater |
| Because of the Scandinavian twin study, most | | | | than having a relative with unilateral breast cancer. |
| experts believed that there are other yet to be | | | | 5. Gender of the relative: If the family member |
| discovered genes involved with breast cancer. | | | | with breast cancer is a man, the risk is higher. |
| Because the chance of having a BRCA mutation in | | | | 6. Other related early onset tumors: If there is a |
| the general population is so low, genetic testing is not | | | | family history of early onset ovarian cancer, this |
| indicated in most patients. However, if a patient has | | | | incurs an increased risk for a person. |
| a family history of breast cancer, then a | | | | |
| mathematical model can be used to determine if | | | | How to decide whether you need the BRCA gene |
| BRCA testing is indicated. The likelihood of being a | | | | test |
| BRCA carrier increases with the number of relatives | | | | |
| who had cancer and if the cancers occurred earlier in | | | | The following is an excerpt from the American |
| life. For example, in families with four or more cases | | | | Society of Breast Surgeons: |
| of breast or ovarian cancer under the age of 60, | | | | 1. Early onset breast cancer (diagnosed before age |
| over 80% are found to have a damaged version of | | | | 50) |
| BRCA1 or BRCA2. If a patient is a carrier of one or | | | | 2. Two primary breast cancers, either bilateral or |
| both of the BRCA1 and BRCA2 genes, her risk of | | | | ipsilateral |
| breast cancer dramatically increases. According to | | | | 3. A family history of early onset breast cancer |
| estimates of lifetime risk, about 13.2% (132 out of | | | | 4. Male breast cancer |
| 1,000 individuals) of women in the general population | | | | 5. A personal or family history of ovarian cancer |
| will develop breast cancer, compared with estimates | | | | 6. Ashkenazi (Eastern European) Jewish heritage |
| of 36-85% (360-850 out of 1,000) of women with an | | | | 7. |