Doctors use a computer program -- a predictive model -- to help them decide which women are most likely to have an abnormal breast cancer gene. Based on the results of the model, doctors may suggest genetic testing for women likely to have an abnormal gene. Insurance companies use the same models to decide who gets coverage for genetic testing.
A study found that two models used to predict BRCA1 and BRCA2 abnormalities aren't very accurate when used on Asian women. This could mean Asian women aren't referred for genetic testing when they should be or that insurance companies don't cover the testing even when it's recommended. The two models looked at in this study are BRCAPRO and Myriad II.
Most inherited cases of breast cancer are associated with two abnormal genes: BRCA1 (BReast CAncer gene 1) and BRCA2 (BReast CAncer gene 2). Women with an abnormal BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70. Abnormal BRCA1 and BRCA2 genes are found in 5% to 10% of all breast cancer cases in the United States.
Factors that increase the risk of an abnormal BRCA1 or BRCA2 gene are:
- personal history of breast or ovarian cancer
- family history of breast or ovarian cancer
- a relative with a gene abnormality
The models doctors and insurance companies use to decide who should get genetic testing consider these and other factors, including ethnicity, to determine a woman's risk of having an abnormal breast cancer gene and whether testing makes sense for her. This study looked at how accurate the BRCAPRO and Myriad II models were in estimating the likelihood that 200 Asian women and a smaller number of white women would have an abnormal breast cancer gene.
- Genetic testing showed that 25 white women had either an abnormal BRCA1 or BRCA2 gene. The BRCAPRO model predicted 24 and the Myriad II model predicted 25. This means both models were just about perfect in predicting the number of white women who would have an abnormal breast cancer gene.
- Genetic testing showed that 49 Asian women had either an abnormal BRCA1 or BRCA2 gene. The BRCAPRO model predicted 25 and the Myriad II predicted 26. This means that the models were only about 50% accurate in predicting the number of Asian women who would have an abnormal breast cancer gene.
- The BRCAPRO model was very bad at predicting an abnormal BRCA2 gene in Asian women. The model predicted only four Asian women would have an abnormal BRCA2 gene, but genetic testing showed that 26 Asian women had an abnormal BRCA2 gene. The Myriad II model doesn't specify whether an abnormal gene will be BRCA1 or BRCA2, so the researchers couldn't determine its BRCA2 accuracy.
If you're an Asian woman and you and your doctor are considering genetic testing based on your personal or family history, ask your doctor about this study. If you're an Asian woman and your doctor has said you don't need genetic testing, you should also discuss the results of this study.
No matter what your ethnic background is, if you know you have an abnormal BRCA1 or BRCA2 gene, your risk of developing breast cancer is higher than the average woman's. You can't change your genetics. But you can make sure that if breast cancer develops it's diagnosed as early as possible. You and your doctor should develop a screening plan designed for your unique situation that includes more frequent screenings that start at an early age and possibly MRI scans or other screening tests. Abnormal breast cancer genes also increase the risk of ovarian cancer, so it's important to discuss this with your doctor, too.
Visit the Breast Cancer Risk Factors: Genetics page to learn more about abnormal breast cancer genes.