In defense of Oncotype DX
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 only data supporting any of them relate to test "accuracy."
In light of the precious little in the way of guidance from clinical trials with respect to best empiric therapy (where the only thing that has been proven to correlate with treatment decisions is reimbursement to the prescribing oncologist) and the importance of basing cancer treatment at least in part on patient preferences, it is entirely reasonable to support judicious application of laboratory tests which have been well characterized with respect to test "accuracy." These are diagnostic tests and should be held to that criteria, and not to that of therapy.
This laboratory test, as well as the others, 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 to the resistance that has been found to chemotherapy drugs.
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.
Cell Culture Assays can report to a physician specifically which chemotherapy agent would benefit a high risk cancer patient by testing that patientís live cancer cells. Drug sensitivity profiles differ significantly among cancer patients even when diagnosed with the same cancer. Knowing the drug sensitivity profile of a specific cancer patient allows the treating oncologists to prescribe chemotherapy that will be the most effective against the tumor cells of that patient.
Every breast cancer patient should have her own unique chemotherapy trial based on consultation of pathogenic profiles and drug sensitivity testing data. 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.