What's a Tumor Marker?

I had heard the term tumor marker before being diagnosed with breast cancer, but didn't really know what it was.  It wasn't until I had completed my breast cancer treatment that my oncologist started using a tumor marker to track my cancer.

What is a tumor marker?  According to Wikipedia, "a tumor marker is a biomarker that is found in blood, urine or body tissues that can be elevated by the presence of one or more types of cancer. There are many different tumor markers, each indicative of a particular disease process, and they are used in oncology to help detect the presence of cancer."

Tumor markers are used in conjunction with other tests, like scans and biopsies, to help diagnose a patient with cancer.  Not all tumor markers are elevated when cancer is present, so oncologists use other screening and diagnosis methods along with tumor markers to confirm cancer.  There are literally hundreds of different tumor markers for specific cancers and many cancers that have yet to be designated a tumor marker.

My type of breast cancer, infiltrated ductal adenocarcinoma, produces a protein that can be detected with the tumor marker CA 15-3.  A blood test is all that is needed to look for that specific protein. Like many tumor markers, there are acceptable levels of the protein and levels that are cause for concern.  With CA 15-3, any score under 32 is considered "No evidence of cancer" and nothing to worry about.  If the level goes above 32, the cancer is probably still active and further treatment necessary.

When I had my first tumor marker test several months after chemotherapy had ended in July 2016, my number was 16.  That is half the acceptable level, so "No evidence of cancer."  That was a huge relief!  Three months later, that number dropped again to 14.  Three months after that it dropped again to 12.  The last tumor marker test in April, 2017 was 14.  We will check it again in August.

Since my tumor markers were staying low, my oncologist chose to have me come every 4 months instead of every 3 months to check my tumor marker.  The number will never drop to 0, but as long as it stays at an acceptable level, no cause for worry.  I won't be given a "cancer free" designation until my tumor marker has stayed acceptable for five years, that means under 32 for five years.

I hold my breath for about a week after I have my blood test and meet with my oncologist for the results.  So far, so good.  I am grateful that my type of breast cancer has a tumor marker that we can use to our advantage.  If at some point my tumor marker becomes elevated, we can decide what to do from there, but I am staying positive that my tumor marker will continue to stay low.