During your cancer journey, you have probably encountered the term ‘’tumor markers’’.
There are two distinct types of markers:
Tumor tissue markers and Cancer biomarkers. Although both are considered ”markers” they are completely different from each other, both in the means of obtaining them and their function.
Tumor Tissue Markers
Tumor tissue markers are found in the actual tumor, obtained by biopsy. Some markers are associated with only one type of cancer, whereas others are associated with more than one cancer diagnosis. Estrogen and progesterone receptors determine whether treatment with antihormone therapy should be considered for treating breast cancer, are examples of frequently used tumor tissue markers. Some markers are used to determine if a patient is likely to benefit from a specific treatment with certain targeted therapies, for example: BRAF mutation for cutaneous melanoma and colorectal cancer patients, HER2 for breast and gastric cancer patients, KRAS mutation for colorectal cancer and non-small cell lung cancer (NSCLC) patients, or PD-L1 for NSCLC as well.
Cancer biomarkers are substances produced by tumor cells or by some healthy cells in response to the tumor. They have moved away from the original cancer site and can be found in the blood, urine, stool, or other bodily fluids of some cancer patients. Therefore, they can be measured in a blood or a urine test. Cancer biomarkers can be used for screening, for monitoring response to therapy or for detecting disease recurrence:
Screening/detecting early cancer- in the last decade, prostate-specific antigen (PSA) was widely used to screen for prostate cancer. Another example is the use of cancer antigen 125 (CA 125) as a biomarker for screening women at high risk for developing ovarian cancer. Recently, a few biomarkers to diagnose bladder cancer gained FDA approval, among them are NMP 22 and BTA that can be detected in the urine.
Monitoring response to treatment- a specific biomarker can be a good indicator of how effective treatment is or has been. Generally speaking, if the treatment is effective, biomarker levels should decrease during or after treatment.
Detecting recurrence- elevated biomarkers levels after treatment, can indicate a recurrence, but not always. The elevation might occur a few months before detection by any clinical or radiological evidence. For example, calcitonin, is a well-known biomarker for thyroid cancer recurrence, or CEA is a biomarker used for detecting recurrence in colon, pancreatic, lung, breast or gastric cancer.
Have you encountered any of these terms ‘’tumor tissue markers’’ or ”cancer markers”? Did you understand them? Was any of it explained by your treating team?