The Oncotype DX Breast Recurrence Score Test looks at how active 21 genes are in a sample of tumour. Those genes influence how likely a cancer is to grow and how it responds to treatment. The result is a single number from 0 to 100.
It is a genomic test, which is not the same as a genetic one. Genetic tests look for inherited mutations linked to higher breast cancer risk and use blood or saliva. A genomic test reads the tumour itself.
Who it is for
Most early-stage, estrogen receptor-positive, HER2-negative breast cancers are treated after surgery with a hormonal drug such as tamoxifen or an aromatase inhibitor. Whether chemotherapy should be added is often unclear. That is the question the test is meant to help answer.
A patient may be a candidate if she has recently been diagnosed with stage I, stage II or stage IIIa invasive cancer that is estrogen receptor-positive. The cancer must be lymph node-negative or have reached no more than three nodes. She and her doctor must also be weighing chemotherapy after surgery.
The test does two jobs. It estimates the risk of the cancer coming back away from the breast, and it predicts whether chemotherapy is likely to help. Studies have found it useful for both.
Reading the score
The ranges depend on menopausal status. For post-menopausal women, whether or not nodes are involved, a score of 0 to 25 means lower risk, and the benefit of chemotherapy is small and likely does not outweigh the side effects. A score of 26 to 100 means higher risk, and chemotherapy is likely to be worth it.
Pre-menopausal women face finer cut-offs. With lymph node-negative cancer, 0 to 15 is lower risk. A score of 16 to 25 falls in the low to medium band, where chemotherapy may offer a small benefit, and ovarian suppression plus hormonal therapy may do as much. Doctors and patients weigh both options. From 26 to 100, the benefit of chemotherapy is likely to be greater than the risks.
With lymph node-positive cancer, a pre-menopausal woman who scores 0 to 25 sits in the low to medium range and may benefit from chemotherapy, though ovarian suppression is again an alternative. At 26 and above, chemotherapy is likely worthwhile.
The score never stands alone. Doctors read it alongside the size and grade of the cancer and the number of hormone receptors on the cancer cells.
The DCIS version
A second test covers DCIS, or ductal carcinoma in situ, a non-invasive form of breast cancer. It analyses 12 genes and also gives a score from 0 to 100. This one estimates the chance that DCIS returns in the same breast, either as DCIS again or as invasive cancer, and whether radiation would help.
Below 39 means low risk, and radiation is likely to bring a small benefit that will not outweigh the side effects. Between 39 and 54 is intermediate, and it is unclear whether radiation is worth the risks. Above 54, the risk is high and radiation is likely to help more than it harms. Candidates are people newly diagnosed with DCIS who are having a lumpectomy or have had a core biopsy.
Cost
Medicare and many other insurers cover the tests. Patients whose plans do not can ask their doctor to work with the insurer. Abbott, which makes the tests, runs a Patient Assistance Program to help people with billing and insurance. Consult your doctor for medical advice.
