Guest guest Posted May 11, 2007 Report Share Posted May 11, 2007 Hi Efrem, A lot of doctors only do the PCR test once a person has reached CCR. FISH tests are not that reliable and they are not very sensitive either. A FISH test will only look at 200-500 cells whereas a PCR test can look at up to a million cells (depending on the lab). That's why you can be zero on a FISH test but not a PCR. The analogy I like to use is this: if you took a swimming pool and filled it up with ping pong balls. You put a trillion white ping pong balls in it (which represent the good, healthy cells) and 10,000 blue ping pong balls (which represent the bad, leukemic cells) in it. Then if you scooped out 500 balls, you could easily find all 500 to be white (good cells) but if you scooped out a million balls, there's a much greater chance that you'll find a few blue ones in there (bad cells). The more cells they look at, the more chances they'll find one that has the bcr/abl protein. In fact, just about everyone still has bcr/abl positive cells, the question is if the lab is using a sensitive enough PCR to detect them. Just because some people show negative on a PCR, doesn't mean they don't have any leukemic cells in them, it just means that the test wasn't sensitive enough to pick them up. Your goal in treatment is to reach a 3 log reduction from baseline which is a thousand fold decrease in bcr/abl cells. Each lab has what they consider to be their baseline so depending on the lab you use, they'll either mark on your report how you compare with that baseline or they'll give you the numbers and you'll have to figure it out yourself. I hope that helps, Tracey > > I know that I have asked this question already but I lost my responses. > > I have been on Gleevec for almost four months and reached cytologic remission last month. My doctor drew some additional blood this past week to now conduct a FISH test and do a PCR for the BCR- ABL protein.. > > Can someone please remind me the difference between the two tests and why we do both. > > Also, my doctor told me that you can be FISH negative but still have the BCR-ABL protein in your body. Can someone please elaborate on that and explain how that is possible, and whatthat means as far as remission. > > Thank You > > Efrem > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted May 11, 2007 Report Share Posted May 11, 2007 A CCR or complete cytogenetic response is when your BMB comes back with 20 normal cells. In the old days, this was the goal of treatment because so few reached it on Interferon. With the advent of Gleevec, patients began getting much better responses so they needed to develop more sensitive testing to track the residual disease. Hence the PCR was born. The experts don't really refer to any reponse as a " remission " because there is no cure for CML and there will always be traces of the disease. This is why they use the word " response " . Once you've reached a complete cytogenetic response (CCR), the next step would be to reach a major molecular response (MMR). This is the 3 log reduction I was refering to in my earlier post. This is the current goal of most patients and doctors. If you reach a complete molecular response (CMR), then your PCR would be negative but again, this is not a " remission " and there are concerns about a negative result to begin with. The concerns with a negative result include; was the test sensitive enough (did it look at enough cells), did the sample arrive in good shape or was it degraded with heat or time and was the test done fast enough or did it sit on the shelf for some time. If these concerns can be eliminated (mostly by using one of the big hospital labs like OHSU), and the result is still negative, then this would be the best you could hope for. I hope that helps explain things, Tracey > > > > I know that I have asked this question already but I lost my > responses. > > > > I have been on Gleevec for almost four months and reached > cytologic remission last month. My doctor drew some additional blood > this past week to now conduct a FISH test and do a PCR for the BCR- > ABL protein.. > > > > Can someone please remind me the difference between the two tests > and why we do both. > > > > Also, my doctor told me that you can be FISH negative but still > have the BCR-ABL protein in your body. Can someone please elaborate > on that and explain how that is possible, and whatthat means as far > as remission. > > > > Thank You > > > > Efrem > > > > > > Quote Link to comment Share on other sites More sharing options...
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