Hello all,
Can someone please help, I'm feelinin a bit dim & struggle to understand the log reduction system.
I was dx at 100% & am now at 0.11
Does this mean that I am at a 2 log reduction, & will achieve 3 log when I fall below 0.1
Have I got this right?
Bob
You are here
Log reduction
I am not an expert but it means currently you are at something like 2.99 log reduction, when you hit 0.1 or lwoer that will be a 3 log reduction or better
i think :S
Hi Bob,
There is a complication in doing the calculation. If at diagnosis time your PCR was 11, then your calculation would be correct.
In order to do your own calculation you need to know what the PCR value is for 100% pH+ at the lab where the test is being run. In my experience it can be anywhere from 10 to 100. The lab that does my test reports in log reduction. There is another lab that I used in the past tht reported pcr values. The number that they used for 100 % pH+ at diagnosis time was 70. This means that 0.7 would be a 2 log reduction at that lab.
In your case 0.11 would be a 2 log reduction if the starting value for your lab was 11 for a patient at 100% pH+.
At one point there was a standard value assigned based on a group of 30 patients at 100%. Somehow ths starting value has been lost, so each lab now calculates their own.
We are still waiting for PCR results to be standardized.
Another factor that needs to be considered is the sensitivity of the test they are using. Some labs are more sensitive than others. You can be PCRU at one lab and only a 4 log reduction at another.
Lets keep watching them go down.
Zavie
Hi Bob,
it is confusing and most of us struggle to understand pcr values in terms of log reductions and we then use that as some sort of measurement of how well we are doing.
Originally the 3 log reduction was taken from on of the earlier studies when samples from 30 patients who were enrolled in the study were used as a benchmark to measure the responses. Obviously those original samples no longer exist so some doctors think that to talk in terms of log reductions can be misleading.
The way I think about is - and this might be wrong but it is my way of understanding it all--
a diagnosis is made at a particular clinic who's lab has a measurement of your PH+ cell population compared with your normal cell population.
If they give this PH+ population a number of 100% then that is a general baseline and is the only one you have. Any reduction from that is good news.... so if you were 100% PH+ at diagnosis and now you are 0.11 then at your particular lab the calculations follow like this:
100.0000 baseline PH + cells population
010.0000 = 90% Major cytogenetic response MCyR
001.5000 = Hammersmith lab consider this the cut off point where PH+ cells are no longer visible under the microscope using the FISH test
Complete cytogenetic response CCyR :
0.1100 = 1 log
0.0100 = 2 log
0.0010 = 3 log and so on.........
0.0000 = Complete molecular response CMyR or PCRu
At this level we know that there is still a population of PH+ cells but they cannot be detected by current technology. In some patients if you reach PCRu and retain it for 2 years or more then you might be able to take part in a study to see if you can stop imatinib. Currently, some patients do maintain this deep molecular remission, some do not and need to take imatinib again.
If I have got the maths wrong then I am sure someone will point it out.... but the best way to think about it is to watch your pcr's fall over time.... the goal is to see a reduction and maintain that reduction in the long term... no matter by how many logs that might be....
I hope this is of some help. Do no get fixated on particular log reductions.
You have done well and should celebrate.
Sandy
Thank you Sandy,
That explains things in a way that even I can undrestand. I was just interested to know where I was. I am just happy that the numbers keep falling & hopefully will continue to do so, but if they stopped now & stayed where they are that would be better than what we had. Time will tell where we go.
Bob
Hi All
I haven't posted for awhile but still read the forum regularly. When I saw this topic it got me wondering about my own situation. On diagnosis, I remember my specialist saying that the FISH study showed 100% PH+ chromosomes which I guess meant that every cell they looked at had the PH+ chromosome. But the PCR done at the time was 58.89%. Is the PCR looking at a different thing? Now I'm unsure. Can anyone help?
Jeanette
Hi Jeanette,
All these numbers certainly can get confusing!
Basically there are 2 ways to measure you progress. One of them is to look directly at your cells to count how many are Ph+ This is how cytology and FISH tests work. The other method is to look for the level of a particular protein produced only by the Ph+ cells. This is what the PCR test does The PCR test can't reliably measure the absolute number of these proteins so instead it looks at the proportion of them against a control protein normally present in the blood.
In your case at your starting point every cell they looked at via the FISH was Ph+ and they found roughly 59 copies of the BCR-ABL protein to every 100 copies of the control protein they found.
With luck your levels of Ph+ cells will quickly become so low that they won't be able to find any actual Ph+ cells by cytology or FISH. They will then have to rely solely on looking for the proteins instead and watching their levels fall. They track the falling level by reference either to your own intial PCR percentage or to an average starting level for the lab that does the test.
The talk about Log reductions is just an added complication to deal with the fact that most doctors are not great at maths and have difficulty with any numbers they can't count on their fingers. The technicians therefore tell them the PCR results in a mathematical shorthand whereby 1 log reduction means a tenth of the base level, 2 log = one hundredth, 3 log = one thousandth etc.