In today’s post, let us look at what kind of biomarker tests are available?
The common biomarker tests that people have use a sample of their tumor. This can be the resected tumor tissue (in people who had surgery 1st) or a tumor biopsy (if surgical tissue is not available) or blood.
The tumor biopsy can be from the diagnostic colonoscopy so the tumor that’s sampled is the primary tumor. Or it can be a biopsy from metastases in the liver, for example.
Is it likely for the primary tumor to be much different from the metastases at the molecular level?
This is a great question and has a nuanced answer. For tumor cells to detach from the primary tumor, travel in the body and seed in a new organ and grow there, it is likely that the tumor cell needed to use many new gene expression programs. So in this sense the tumor cell in the metastasis is likely different from a tumor cell at the primary tumor. Most tumor tests only report mutations that are known to be relevant in cancer and mutations known to be important in colorectal cancer. How likely are these mutations to be much different between a primary tumor and metastases? As far as mutations that are actionable or targetable, it is unlikely that these mutations are much different between a primary tumor and a metastases. So the answer to the question above is yes, but most such changes may not make a difference in treatment decisions. So testing either the primary tumor or a met is quite acceptable to learn about the tumor mutations that are targetable or those that would result in changing treatment strategies.
Here is a nice paper to read on this topic:
So now you know your biomarkers and what they mean for you etc.
But did you know that there is a simple way to keep track of your actionable biomarkers?
Steve Schwarze, who was the COLONTOWN Mayor and Cabinet member had a brilliant idea..
He created this that anyone can use. Go to COLONTOWN University click below:
How often should the tumor testing be done is a question I have heard people ask as well.
As I understand, if your tumor has only been exposed to chemo and a biologic like bevacizumab or Avastin, it is quite likely that over 3-5 years your tumor may have not changed too much molecularly to make it now targetable with new targeted therapies. So testing your tumor (if mets are in an accessible place) or blood more frequently may not be needed.
But if you are on EGFR inhibitors like Cetuximab or Panitumumab or if your tumor has a BRAF mutation and you have been on targeted therapy for it, checking if your tumor has evolved and developed new mutations may be important to learn. In such cases, more frequent testing for tumor biomarkers in blood may be important.
When is a good time for a repeat test is another common question people have.
From what I have seen, when people have progression while on EGFR inhibitors or other targeted therapy or they were on a clinical trial for targeted therapies and have progression, this is a good time to repeat a tumor genomic testing, perhaps using a liquid biopsy.
We will discuss this in more detail in another post.
Please share your experiences or questions around this topic.
I will be back soon with another post. Until then, take care!
#ToLife #ToScience
— Dr. George