saltygirl wrote:How does cancer mutate? Can you have an original tumor with Kras. But metastases no mutations? Or reverse? Do most cancers eventually mutate? Just curious to learn more about mutations.
DK37 wrote:In 2016, O Stoma Mia wrote:
Here are some of the types of questions that I have:• MSI status – is it a property of patient or a property of a tumor? Some of the writings on the topic of MSI testing refer to “MSI patients” while other passages refer to “ MSI tumors”. So, is MSI status something that a patient has always had (like blood type), and if so can this be assessed at anytime during lifetime – for example could MSI status be assessed for a fetus by doing amniocentesis in the same way that Down’s Syndrome is assessed before childbirth, etc,?
• MSI status for tumors – Does MSI testing require a tumor? If so, does it make any difference whether it is the primary tumor or a metastatic tumor?
• MSI status for tumors – within-tumor variability - If MSI testing is done on tumors, then can the specimen from one part of the tumor turn out to be MSI-High while a specimen from a different part of the same tumor turns out to be MSI-Low?
• MSI status for tumors – tumor location - If MSI testing is done on metastatic tumors, and if the patient has several such tumors (eg., one in liver and one in lungs) then can one of these tumors test as MSI-High while the other tumor tests as MSI-Low? Can MSI testing on a primary tumor yield different results from MSI testing on a metastatic tumor?
• MSI status test-retest reliability - If MSI status is determined as MSI-Low on one testing, what is the likelihood that it will turn out to be MSI-High when a second test is done on the same sample? What if different labs give different results when they are doing tests on the same tumor?
• MSI testing sample requirements - What is minimally needed in order to do MSI testing? Can this be done on a blood sample or on a urine samle, or does it have to be done on a sample from a tumor? If it requires a tumor, then does it have to be a primary tumor, or a metastatic tumor, or does it make any difference? Can an MSI test be done on a pre-cancerous polyp, for example?
• MSI testing – specimen preservation requirements. If MSI testing requires a specimen taken from a tumor, does it make any difference how the specmen was preserved? What if it was not preserved in a paraffin block, but was preserved in a bottle of formaldehyde or in some non-standard manner? In other words, are there industry-wide standards on specimen preservation that must be met before MSI testing can take place? Prior to surgery, does the surgeon need to be informed that MSI testing will be needed so that he/she will be sure to preserve the specimen in the proper manner to allow subsequent MSI testing?
• MSI testing when tumor specimen is not available - What if the requirement is for a tumor sample, but the patient has been NED for 5 or 10 years, does not have any visible tumors any more, and the original resected/biopsied tumor is no longer available? Can MSI testing still be done, for example, by testing the Circulating Cancer Cells in the blood instead, or by using some other method?
• MSI testing for family members. If a patient has received his/her MSI testing results and now wants to have family members tested for MSI status, is this at all possible if the family members have never been diagnosed with cancer?
• MSI status stability - If a patient is tested for MSI now, in 2016, will these results still be valid 5 or 10 years from now, or could the patient’s current MSI status change after being subjected to 4 or 5 years of continuous chemo regimens of one type or another?
Absolutely fantastic questions O Stoma Mia! You are much better than some formally trained molecular biologists!! I'll try to gather answers for them
Cheers,
-DK
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