Hi Ian... it is always confusing and after 12 years I still suffer! I think that it is only useful to talk about log reductions on a molecular level... i.e not when calculating how big a cytogenetic response you have had.
if you were 68.9- let's say 70% - bcr/abl at diagnosis then really you could probably say that you were more or less 100% PH+. you are now 1.40% bcr/abl which, according to the European Leukaemia Net guidlines for molecular monitoring, means that you are just about at the level where you would be deemed PH negative. Currently the cut-off is 1 to 1.5% bcr/abl
So according to how I understand the nomenclature you have achieved a Complete Cytogenetic Response or CCyR within 3-4 months which is GREAT and represents an 'optimal' response.
Log reductions would now be the calculation that would kick in. i.e if you are at
1.40% now and your next pcr shows
0.14 then that would represent a 1 log reduction
0.014 would be 2 log
0.0014 would be 3 log etc etc until you reach bcr/abl Undetectable or as many patients call it PCRu
Of course I might be totally wrong but this is the way I have understood the usefulenss of using log reduction as a measurement.
It was first used in the IRIS trial to measure responses against the pre therapy bcr/abl levels of 30 patients who were part of that trial. It seems to have stuck with us as a measurement although it is not really applicable now as all the original samples of those 30 patients have long been used up.
Hope this is helpful and not even more confusing.
Sandy
