Oncotype DX Test in Colon Cancer

Oncotype DX, one of the newest tests used for patients with stage II colon cancer, may serve as a guide for making the right treatment decision.

Similar to the test used for patients with early-stage breast cancer, Oncotype DX is a test performed after surgery. However, the final decision is made according to the course of adjuvant (preventive chemotherapy) treatment administered after surgery. This test determines the risk of cancer recurrence by evaluating the activity of certain genes in a sample taken from the tumor tissue. Because stage II colon cancer carries an approximate recurrence risk of %25, the Oncotype DX test is important during the decision-making stage. The risk probability identified by this test will help determine an individualized treatment plan. Adjuvant chemotherapy administered after surgery is not routinely recommended for all patients with stage II colon cancer. This type of treatment is considered for patients at high risk. Therefore, it is extremely important to identify patients who will truly benefit.

The Oncotype DX colon cancer test was developed by Genomic Health. 3 major steps were completed during the development of the test:

1. Colon cancer genes were investigated. In research conducted by Genomic Health, a group of genes related to colon cancer was examined using research tools capable of measuring RNA levels in certain genes.
2. Clinical studies were conducted. Research was performed on the identified genes to determine those most closely associated with the risk of colon cancer recurrence.
3. A test was developed to determine the risk of recurrence. An algorithm was created after samples from more than 1.800 patients were examined. The formula generates a numerical recurrence score based on results indicating the likelihood of colon cancer recurrence.

Gene expression analysis technology and the algorithm are the two key components of the Oncotype DX colon cancer test. Clinical studies involving more than 2.100 colon cancer patients confirmed the validity of this test. This carefully designed series of procedures is a standardized testing method that is informative and enlightening for physicians in determining the correct diagnosis and treatment method, while also offering patients potential benefits on the path to recovery.

The Oncotype DX Colon Cancer test is a new method used to determine the risk of stage II colon cancer recurrence by evaluating the levels of 12 genes in the tumor obtained during a biopsy or surgery performed on a patient with colon cancer. How or to what extent these 12 genes are active is investigated. Test results are given as a numerical recurrence score indicating the likelihood of cancer recurrence, ranging from 0 to 100. In addition, the mismatch repair test performed by immunohistochemistry on a colon tumor sample will play an influential role in your doctor’s decision regarding the treatment method.

Chemotherapy administered after surgery is performed to prevent colon cancer from recurring. The likelihood of colon cancer recurrence is another factor that plays an important role in the decision regarding chemotherapy after surgery in patients with stage II colon cancer.

Determining Whether the Oncotype DX Test Is Appropriate for the Patient

The results of the Oncotype DX® Colon Cancer test, an effective testing method for determining the likelihood of cancer recurrence in patients with early-stage colon cancer, are used to develop a treatment plan after surgery. The checklist below may help determine whether you are a potential candidate for the Oncotype DX Colon Cancer test.

If;

• you have been diagnosed with stage II colon cancer and have undergone your initial surgery,
• you have recently been diagnosed with stage II colon cancer and are discussing chemotherapy treatment options with your doctor,

this means that you may be a candidate for the Oncotype DX Colon Cancer test.

The necessity of the Oncotype DX test, which is appropriately performed only before chemotherapy treatment, is a decision that must be made by your doctor based on the examinations performed. In addition to standard tests, this test also helps identify features such as T stage, lymph node involvement, test score, and mismatch repair, which are used to evaluate the patient’s needs. In this way, the doctor and patient, having made the best individualized treatment decision, can help increase the rate of successful effective treatment.