According to the National Human Genome Research Institute, "genetic testing" covers a wide variety of clinical and non-clinical tests and includes testing of DNA, RNA, and proteins. Breast cancer genetic tests use blood samples or tissue samples to assess these genetic components to predict future breast cancer occurrence and breast cancer recurrence, and to guide treatment decisions.
Predictive Testing:
Predictive genetic testing identifies inherited gene changes, or mutations, which increase the risk to develop breast cancer. These breast cancer genetic mutations involve inheriting an increased risk for breast cancer, not inheriting the disease itself. Thus, this type of genetic testing determines future breast cancer risk for women who have had breast cancer as well as for women who have never had any type of cancer.
All of the predictive genetic tests for breast cancer use blood cells to sequence genes looking for DNA mutations. The tests available are for a number of different genes including the BRCA1 and BRCA2 genes. These two genes account for nearly half of inherited breast cancer. Alterations in other genes also increase the risk for inherited breast cancer, although according to the National Cancer Institute together these account for 5% or less of all inherited breast cancer.
Cancer Biomarker testing:
Breast cancer biomarker measures the level of various gene products or proteins, made by cancer cells, and reflects the presence of or severity of breast cancer. For example, rising blood levels of the protein carcinoembryonic antigen (CEA) indicate breast cancer recurrence, and CEA levels thereby monitor a patient after cancer treatment.
Kerlikowski and colleagues reported in April 2010 that new biomarkers might soon be available to determine which ductal-carcinoma-in-situ cancers progress to invasive breast cancer.
Pharmacogenetic testing:
Pharmacogenetic testing assesses acquired genes mutations or protein levels to determine cancer treatment. An example of pharmacogenetic breast cancer testing includes HER2/neu, also called HER2. For breast cancer patients, the breast cancer tissue sample obtained at biopsy or at surgery is tested by immunohistochemistry or fluorescence in situ hybridization to assess the protein levels of HER2. Only those patients whose cancers test high for HER2 receive the drug Herceptin.
HER2 is also one of the genes tested in Oncotype DX. This multigene test assesses over 20 different genes in breast cancer tissue, and provides a breast cancer recurrence score and prediction of whether certain breast cancer patients will benefit from chemotherapy.
References
- National Human Genome Research Institute: Issues in Genetics: Genetic Testing
- Genetic Home Reference: handbook: genetic testing: What are the types of genetic tests?
- Mayo Clinic: Diseases and Conditions: Breast cancer types: What your type means
- National Cancer Institute: Genetics of Breast and Ovarian Cancer: Other Rare Breast and Ovarian Cancer-Associated Syndromes
- National Cancer Institute: Genetics of Breast and Ovarian Cancer: Low-Penetrance Predisposition to Breast and Ovarian Cancer
