Measuring the response to therapy for CML patients is done by blood and bone marrow testing. This testing is critical to CML patients as the greater the response to drug therapy, the longer the person’s disease can be controlled. Other things that factor into the equation include the stage and features of the person’s CML at the time of diagnoses.
At the end of this week I will be seeing my doctor again. He will be performing the usual CBC with differential and an additional blood test called a Quantitative PCR (Polymerase Chain Reaction) test. A PCR test had not been done when I was first diagnosed, or on subsequent doctors’ visits, so the last time I saw him I had my first PCR; which gave us a baseline. I am anxious to have this second PCR performed because it will actually tell me how my blood is responding to treatment thus far.
There are four different stages of response for blood cancer patients. I will discuss two of them today and the other two tomorrow. Nearly all people undergoing treatment will reach the first response level which is called a “complete hematologic response” (CHR)) This response is achieved when immature CML cells are eliminated from detection in the blood; the white cell count is no longer elevated, the platelet count is in the normal range and the spleen is no longer enlarged. This test result is monitored by a simple blood test. The goal during early treatment is to decrease the number of chronic myelogenous cells to one-tenth of the level at the start of treatment. My guess is that I have quite possibly reached this goal as I had 380,000 white cells when I was diagnosed and I currently have only 4,200 now.
Another stage of response is the “major molecular response” (MMolR). This is monitored by the blood test called the quantitative PCR. This is the one that I am excited about! This test is a bit more confusing to understand, but what its’ test results show, is your response to treatment. The goal is to have a 3-log or greater reduction in Bcr-Abl RNA or DNA in the blood and marrow. A 3-log reduction is a 1/1,00 or 1,000 fold reduction of the level at the start of treatment. Since the test had not been done at the start of treatment, we will be using my last test done three months after I began treatment.
My PCR result was 5.9 x 10-2, for all of you veterans out there I am sure that you understand these numbers better than I do. I know that what I want to see on my next test is a reduction from there. I am hoping that my respite of ten days without my Sprycel, thanks to my lingering bronchitis, doesn’t cause an increase in these numbers. I am hoping that my diligent dose, at 10:30 am every day with the exception of those ten days will show a HUGE reduction in Bcr-Abl levels; Why not shoot for the moon, right?