Genomic Health, a life science company in California, offers Oncotype DX testing. This 21-gene assay provides prediction of chemotherapy benefit for breast cancer patients, as well as recurrence. Validated, the test allows physicians and patients to make more informed treatment decisions. However, the test only applies to patients with certain cancer characteristics. According to the Mayo Clinic, this limits the test's usefulness, as it applies to only a small number of patients.
Medical Endorsement
The American Society of Clinical Oncologists states that the medical usefulness of Oncotype DX lies in predicting risk of recurrence and identifying which patients to spare chemotherapy. The National Comprehensive Cancer Network similarly states that the option of using Oncotype DX to guide chemotherapy treatment decisions applies for patients with cancers meeting the criteria.
Patient Eligibility
Patients benefiting from Oncotype DX testing include those with early-stage invasive, lymph node-negative and estrogen receptor-positive breast cancer. Stage I or Stage II invasive breast cancer indicates small tumor size and cancer cells beginning to invade neighboring normal tissue. Note that patients with carcinoma in situ, such as ductal carcinoma in situ, or DCIS, would not benefit. These cancers are Stage 0, and they do not invade other tissue. Patients with more advanced stages of breast cancer involving spread to the lymph nodes or to other body parts beyond the breast also do not benefit from Oncotype DX. Further, patients having Oncotype DX generally have breast cancer that tests positive for estrogen receptors or progesterone receptors, called ER positive and PR positive, respectively.
Genes
The Oncotype DX test analyzes a panel of 21 genes within a tumor sample. The categories of genes include proliferation and invasion. These types of genes control growth of cells and make more copies of cells, as well as control the cell's ability to spread. Other gene categories in the Oncotype DX test include HER2. According to the American Association for Cancer Research, the HER2 gene, or human epidermal growth factor receptor 2, also plays a role in regulating cell growth. Oncotype DX genes also include estrogen receptors, progesterone receptors and other hormones.
Tissue Sample Needed
Oncotype DX uses breast cancer tissue, usually obtained during a lumpectomy, mastectomy or core biopsy. After surgical collection, the sample processing involves putting the tissue into paraffin wax, which preserves it for future diagnostic testing. A health care provider orders Oncotype DX to be done with the tissue already obtained, and thus requires no additional procedure. Upon ordering the test, a pathologist uses the tissue in the paraffin and slices several thin sections to send to the company. As such, Oncotype DX uses only a small part of the tissue sample.
Results
The Oncotype DX results give a number between 0 and 100, not categorized into "high" or "low" values. The score corresponds to a likelihood of breast cancer recurrence within 10 years and indicates response to chemotherapy. With physician interpretation, this information provides a personal result for the patient.
