Using Tumor Markers to Select the Best Cancer Treatment
What if a dependable way could be found to identify which cancer treatment would most likely work for you? Researchers are studying tumor markers—substances found in the body when cancer is present—to give doctors the tools and knowledge to predict how individual patients are likely to respond to cancer treatments. For certain cancers, tumor markers already can help guide the best choice of treatment.
One of the major challenges in treating cancer is that each individual’s cancer is unique: no two tumors are exactly alike, even after the same diagnosis. For this reason, treatment that is effective for one individual might not work for another. Cancer cells contain an individual’s unique set of genes (biologic units of heredity). In addition, they contain oncogenes (cancer-causing genes). Different cancer cells may contain unique combinations of genes and oncogenes.
Tumor markers are often proteins produced by the cancer cell as a result of oncogene activity. They may be detected through laboratory testing of blood or urine samples, or with biopsy (tissue) samples. Researchers would like to know which tumor markers can be detected in cancer cells that are responsive or resistant to treatment. This would help them predict how a tumor will behave in response to chemotherapy or other treatments. It also would help them identify the best treatment option for that particular cancer.
Breast Cancer
Tumor marker testing is already in use for selection of certain treatments. Since 1998, Herceptin® (trastuzumab) has been approved for treating women with breast cancer tumors that overexpress (produce unusually high levels of) the HER2 protein. Tykerb® (lapatinib) was recently approved in combination with another cancer drug, Xeloda® (capecitabine), as treatment for advanced HER2-positive breast cancer.
Colorectal Cancer
Erbitux® (cetuximab) and Vectibix™ (panitumumab) are drugs that act against the epidermal growth factor receptor (EGFR) and are used to treat colorectal cancer. Researchers have reported that the EGFR-targeting drugs Erbitux and Vectibix are much more likely to be effective in patients with advanced colorectal cancer (cancer of the large intestine).
Vectibix is more effective for treating patients with advanced colorectal cancer (cancer of the large intestine) if the cancerous tumors do not have mutations of the KRAS oncogene.Investigators have also shown that patients with advanced colorectal cancer are much more likely to respond to Erbitux if their tumors do not have a mutated version of KRAS. Knowing this, doctors can use the presence or absence of KRAS oncogene mutations as a tumor marker for identifying patients with a better chance of responding to Vectibix or Erbitux treatment. To learn more about tumor markers in colorectal cancer, click here.
How do I get tested for tumor markers?
- Talk to your health care team. Depending on your type of cancer, they may have already included testing for tumor markers in your diagnostic evaluation.
- If your health care team does not believe tumor marker testing is appropriate for you, ask why. (There may not be enough known about tumor markers for your cancer diagnosis.)
- Ask if consultation with experts in tumor marker research might help (as long as this does not interfere with treatments recommended for you that are known to work).
- Find out if your health insurance covers the cost of tumor marker testing for use in guiding treatment.
Questions to Ask Your Doctor about Tumor Markers
Should I be tested for tumor markers?
Do you routinely use tumor markers to help patients with my cancer diagnosis?
Under what circumstances would you use tumor markers to guide my treatment?
How would the presence or absence of tumor markers affect the choice of therapy for me?
Is there any research on tumor markers related to my cancer diagnosis?
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