3 replies to this topic

[Tedsey]

I am under the impression that FISH and Karyotyping look for the same thing.  Except a BMB is more accurate.  Why do oncs still do FISH?  I have never had a FISH done and I have been to two large cancer centers associated with two large universities.  Why do some oncs use them and other's don't?  What is the value of the FISH vs. Karyotyping?

[Trey]

The karyotyping (chromosome analysis) done during a BMB can spot a number of abnormalities in the chromosomes, but a FISH will only look for a specific issue it is told to look for (using "probes" specific for some issue).  Then a separate FISH would need to look for another issue.  So FISH is a very narrow karyotype tool looking only for narrow issues, and will not show other issues that might be present.  FISH is useful when the Onc already knows you have CML, so a FISH can be run that specifically looks for the Philadelphia Chromosome.  Or a certain FISH can look at some other detailed chromosome issue.  Sometimes just looking to see everything that is present in the chromosomes is a better approach, which is what the BMB does.  And a BMB does more then karyotyping.  It also looks for marrow fibrosis and other marrow problems.

For example, if a person has a BMB done to diagnose CML, the BMB karyotype would show the Philadelphia Chromosome, and if they also had a Trisomy 8 chromosome mutation, the BMB would see that also.  A CML FISH would only see the Philadelphia Chromosome.  A separate FISH could look for Trisomy 8, but how would anyone know to look for it?

A FISH is a useful tool when someone is having difficulty achieveing CCR (zero BMB or FISH).  The FISH is less intrusive, so easier to use on a regular basis.  And it may be a little better than PCR since it is a direct check on percentage of leukemic cells.  After CCR the FISH is useless unless there is loss of response, so PCR is better.

Overall, for your issues Tedsey, FISH would actually be a good tool for monitoring your progress.  Probably better than PCR, which has not been very useful for you, given changes in labs, etc.  FISH results can be compared directly from all labs, unlike PCR.

http://en.wikipedia.org/wiki/Karyotyping

http://en.wikipedia.org/wiki/Fluorescent_in_situ_hybridization

[Tedsey]

Thanks Trey.  I get another PCR this month.  Since the e1a2 was not discovered at dx and it only showed up in my recent BMB and not the PCR four days earlier, I will ask my onc about it.  Can FISH look for e1a2?

[Trey]

FISH does not distinquish among breakpoints, it just counts them all.  PCR can distinquish various breakpoints (as long as it looking for more than just b2a2 and b3a2), so continuing PCRs are also a good idea for you.