atlanta1 Posted December 20, 2007 Share Posted December 20, 2007 Does anyone know if CT and pet scan measurements are comparable? My dad had ct 10/14, PET 10/31 and another CT 12/13. He has had two treatments of carboplatin/taxol. His oncologist is wanting to switch out chemo drugs based on measurements between ct #1 and CT #2 where a tumor on his liver is larger - but if you consider the Pet measurement vs ct #2 - the liver tumor is smaller (liver biopsy is non small cell adenocarcinoma). Of course we are not thinking fast enough in the doctor's office to consider this - today was a frustrating day it seemed like the oncologists office wasn't quite together. It was very busy maybe they were trying to see everyone before the holidays. Thanks for any input. Quote Link to comment Share on other sites More sharing options...
cat127 Posted December 20, 2007 Share Posted December 20, 2007 the PET is not an accurate measurement of size. there is a CT component to the PET, but it is not the same as the regular CT you get. just speaking from work experience where i know we would not look at a PET/CT as proof of change in a tumor size, we would require a dedicated CT to monitor tumor change/shrinkage/progression. you may want to ask dr west, but my work experience agrees with your drs take, that the information from the CTs are the more accurate measures. also, i would recommend you calling the dr and asking them, they should be happy to explain to you their thought process so you can decide for yourself if it seems acceptable. Quote Link to comment Share on other sites More sharing options...
AndyT Posted December 20, 2007 Share Posted December 20, 2007 Amy, I have no firsthand knowledge, but can give you my Dad's Oncologist's opinion. I asked her if Dad's 1st follow-up would be PET or CT. She said CT as it gives her better data to use to track response. She uses PET to determine spread/activity not tumor size. Sorry to hear that your Dad's initial response wasn't what you had hoped for. Hang in there!! Andy Quote Link to comment Share on other sites More sharing options...
john Posted December 20, 2007 Share Posted December 20, 2007 CT is for measuring size and how it looks. A PET measures the metabolic activity. In the past PET was not used to determine if tumor was responding to chemo. Recently I believe there has been studies that indicate PET can be used to measure response to chemo. PET uses a measurement called SUV (Standardized uptake value). This measures the amount of uptake by tissue of the sugar. A SUV of greater than 4 (may indicate a tumor) I don't think you can compare CT to PET. It is like comparing apples to oranges. You could compare PET#1 vs PET#2. Quote Link to comment Share on other sites More sharing options...
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