Breast Cancer

Tumor Markers

Tumor markers are substances, such as genes, proteins or molecules, which are produced by cancer cells or other cells of the body in response to cancer. They can be measured in the blood, plasma, urine, cerebrospinal fluid or other body fluids or tissues. Tumor markers are also known as biomarkers, molecular markers, biological markers or serum markers.

Research into identifying tumor markers is changing the way doctors identify, diagnose, stage and treat certain types of cancer. Targeted therapy is a type of treatment used because it “targets” specific tumor markers in an attempt to kill the cancer cells or stop them from growing.

How Tumor Markers Are Used

Tumor markers may be diagnostic, prognostic or predictive. Diagnostic tumor markers help doctors determine the type or subtype of a tumor. However, tumor markers are not the sole tests used to diagnose cancer. They typically are used along with other blood tests, biopsies and imaging scans. A prognostic tumor marker provides information about a person’s overall cancer outcome, regardless of therapy. A predictive tumor marker helps doctors guide and monitor a specific treatment approach. Some tumor markers may also help to determine how aggressive (fast-growing) a tumor is or monitor for cancer recurrence.

Your doctor will recommend the kind of testing that is best for you. To test for a tumor marker, your doctor will take a sample of your blood, tumor or other bodily fluids. These samples are sent to a laboratory where they are tested, and results are returned to your doctor.

Breast cancer tumors vary in several important ways. The presence of tumor markers and genetic profiling on breast tumor tissue has led to additional classifications of breast cancer according to subtypes based on molecular or genetic changes.

Common Types of Tumor Markers

Tumor markers and genetic mutations offer insight into breast and gynecologic cancers.

  • BRCA1 and BRCA2 (breast cancer 1 and breast cancer 2) are genes that both men and women have. However, when people inherit a mutated version of either of these genes, their risk of developing breast cancer increases. Testing positive for either of the BRCA1 or BRCA2 mutations also raises the risk for ovarian, fallopian tube and peritoneal cancers. BRCA1 and BRCA2 cause a condition known as hereditary breast and ovarian cancer syndrome.
  • CA-125 is a standard tumor marker for ovarian, fallopian tube and primary peritoneal cancers. High levels of CA-125 in the blood may also be found in lung, pancreatic, breast, liver, colon and uterine cancers, as well as in some noncancerous conditions.
  • ER and PR (estrogen and progesterone receptors) are hormones that circulate naturally in the body. They send signals to special receptor proteins inside normal breast cells. These normal breast cells depend on estrogen and/or progesterone to grow. Estrogen and progesterone hormones can also send signals to some breast cancer cells (those that carry the ER and/or PR tumor markers) to “turn on” the growth of breast cancer cells. Breast cancers are classified according to the presence (ER+/PR+) or absence (ER-/PR-) of these receptors in the cells, and the amount (or expression) of receptors. Blocking of these receptors by drugs can decrease tumor growth.
  • HER2 overexpression occurs when multiple copies of the human epidermal growth factor receptor-2 (HER2) gene are present (known as gene amplification). The protein sends signals that increase the growth of breast cancer cells. High levels of HER2 are associated with fast-growing tumors that are more likely to recur. Breast cancers with overexpression of HER2 are likely to respond to treatment with an anti-HER2 agent that prevents HER2 from sending signals.

Genetic Testing

Genetic testing is an analysis of a person’s genes, proteins and chromosomes and is designed to look for inherited gene abnormalities (changes, alterations or mutations) that may increase the risk of cancer. Genetic testing can be done by analyzing a variety of different tissue samples but is most frequently based upon blood, saliva or swabs from inside of the mouth. After being examined in a laboratory, the results are sent back to your doctor and/or genetic counselor, or may be sent directly to you. Decisions to pursue genetic testing are complicated for emotional, financial and technical reasons. It is, therefore, useful to have a consultation with a trained genetic counselor before, as well as after, undergoing the testing so that the results are interpreted properly. Genetic tests are usually requested by a doctor or other health care provider, but the decision to have genetic testing is a personal one that should be discussed with not only your doctor and genetic counselor, but also your family. There are several strong “indicators” that may encourage you to investigate genetic counseling.

Consulting with a genetic counselor before testing will help you understand your risks for other cancers. After testing, your counselor can help you interpret the results and use them to plan future health care, such as a schedule for screenings. If a genetic mutation is identified, your genetic counselor may discuss options to reduce your risk, including earlier or more frequent screenings, lifestyle changes or preventive treatments.

Your doctor may strongly encourage you to share the results of genetic testing with your family. A positive result may confirm a hereditary cancer syndrome and/or indicate a higher chance of a mutation in a first-degree relative (sibling, child or parent). Understanding your results will allow family members to make more informed decisions about their own health care and lifestyle. It’s important to remember, however, that genetic test results provide clues regarding likelihood of cancer developing in an individual, but they do not provide 100% certainty. A person with a negative test result, therefore, may still develop cancer, and some individuals testing positive for a mutation might not develop cancer. Furthermore, the genes that have been linked to cancer risk can have a variety of different types of mutations or abnormalities, and some of these abnormalities are more strongly associated with cancer risk than others.

Genetic testing can be expensive, and the cost depends on several factors, such as the complexity of the test and how many family members are tested. The initial testing is usually the most expensive, but once a mutation is identified in a family, the cost may drop significantly for relatives who are tested subsequently because they can undergo targeted testing to look for the previously-identified specific mutation. Medicare and private health insurance cover testing in most cases, but always investigate your insurance coverage first. Some testing laboratories are also able to help verify insurance coverage before testing is done.

Though genetic testing can be helpful in some cases, it’s important to note that most cancers occur because of changes or mutations to a gene as a result of an outside cause rather than a hereditary genetic abnormality. For instance, exposure to sunlight or tobacco may cause gene changes, or gene changes can be the result of other random events with no definite cause.

Many people who have a family history of cancer worry about hereditary risk, but most cancers – even those within a single family – occur simply by chance. In fact, only 5-10 percent of cancers are strongly linked to inherited genetic mutations.

Additional Resources

 

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