Oncotype DX is a diagnostic test that quantifies the likelihood of disease recurrence in women with early stage, node negative breast cancer. With the information provided by the test it may be possible for doctors and patients to make more informed decisions about breast cancer treatment options.
Oncotype DX analyzes a specific set of genes within a tumor to determine a recurrence score. The recurrence score is a number between 0 and 100 that corresponds to the likelihood that a recurrence with happen within 10 years of initial diagnosis.
Results presented at the 2006 annual San Antonio Breast Cancer Symposium (SABCS) stated that the Oncotype DX test can more accurately predict estrogen receptor (ER) status than the two other commonly used tests, immunohistochemistry and ligand binding.
Another Oncotype DX study presented at the SABCS said that the test could predict the response to Tamoxifen by the levels of estrogen expression.
The researchers concluded that ER and PR expression, as measured using the Oncotype DX test, provide different pieces of information about prognosis and likely response to Tamoxifen among patients with node-negative breast cancer.
1. Oncotype DX can measure the activity of dozens of genes and reveal which ones are most active. The test is expensive, but many insurers cover it because it often prevents even more costly and unnecessary chemotherapy.
Predictive "accuracy" is the data existing to validate the Oncotype DX test. However, the traditional criteria ever used to evaluate laboratory tests has been the predictive "accuracy" of the test. None of the available laboratory tests used in the selection of treatments for cancer patients have ever been tested for "efficacy." This includes estrogen receptor, progesterone receptor, Her2/neu, Oncotype DX, EGFR amplification/mutation, immunohistochemical staining for tumor classification, Cell Culture Assays, Bacterial Culture and Sensitivity Testing, CT, MRI and Pet Scans to measure tumor response to treatment.
The Oncotype DX test is a tool for the oncologist. The oncologist should take advantage of all the tools available to him/her to treat a patient. And since studies show that only 25-30% of patients do respond to chemotherapy that is available to them, there should be due consideration to looking at the advantage of molecular and cellular assay tests.
For the vast majority of cancer patients, the cancer will not recur regardless of whether they receive chemotherapy. So they are exposed needlessly to the treatment, which can cause myelosuppression, mucositis, cardiac problems, peripheral neuropathy, central neurotoxicity, or leukemia. Doctors cannot tell, however, which patients needed the chemotherapy.
Because of this, there is a good portion of cancer patients that are either undertreated or overtreated because there was no adequate information on who will recur. The Oncotype DX is another test to enhance the ability to distinguish between low risk and high risk patients. Patients in the high-risk group, who would benefit from chemotherapy can then be pre-tested to see what treatments have the best opportunity of being successful, and offers a better chance of tumor response resulting in progression-free survival, while those in the lower-risk groups can be spared the unnecessary toxicity, particularly associated with ineffective treatment.
Research and application of these tests are being encouraged by growing patient demands, scientific advances and medical ethics. These tests are not a luxury but an absolute necessity, and a powerful strategy that cannot be overlooked.
Posted at 9:35PM on Dec 21st 2006 by Gregory D. Pawelski