With breast cancer, your doctor may recommend a 21-gene test. Depending on the type of cancer you have, this test can indicate whether the cancer is likely to come back at some point. This helps doctors choose the right treatment strategy from the start of treatment.21 Genetic testing is often a deciding factor in whether a patient needs chemotherapy.
Who should be tested?
21 Genetic testing does not require additional procedures for the patient and can be done by the doctor using tissue specimens obtained during a biopsy or surgery. Your doctor may recommend this test if you have:
- Stage I or II invasive breast cancer;
- Breast cancer that is estrogen receptor positive (ER+), meaning the cancer cells can grow in response to estrogen;
- No lymph node metastasis.
If ductal carcinoma in situ (DCIS) is diagnosed, it may also undergo 21 genetic testing, which can help determine whether to proceed with radiation therapy.
What do the test results mean?
The 21-gene test will analyze 21 different genes within the cells of a tumor sample, some of which suggest that the cancer is more aggressive and more likely to come back after treatment. The test results are displayed on a scale of 0 to 100.
Breast cancer that is not intraductal carcinoma in situ
- Score no greater than 17: means that if treated with endocrine therapy, the cancer is at low risk of recurrence and chemotherapy may not be needed to prevent recurrence.
- Score 18 to 31: means the risk of cancer recurrence is moderate and chemotherapy may be helpful to prevent recurrence.
- Score > 31: represents a high risk of recurrence and may require concurrent chemotherapy and endocrine therapy.
Intraductal carcinoma in situ
- Score no greater than 38: represents a low risk of cancer recurrence and the risk of radiation therapy will outweigh the benefit.
- Score 39-54: means the risk of cancer recurrence is moderate and it is not clear whether radiotherapy will help.
- Score > 54: represents a high risk of cancer recurrence and the patient may benefit most from radiotherapy.
21 Genetic testing is not the whole story
Of course, genetic test results alone are not enough to decide on treatment. Doctors also consider the size and stage of the tumor, the number of hormone receptors in the tumor, and the patient’s age before recommending a treatment plan.
In addition, there are genetic tests that have shown promise in guiding early breast cancer treatment, but more research is needed.
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