Q-PCR testing timelines depend on the lab where your sample is tested. Generally, 3-4 weeks is not an unusual amount of time to wait for Q-PCR results in the UK.
As you are so newly diagnosed waiting for test results creates a lot of anxiety. However, a Q-PCR test is a very sensitive test and is quite complex to perform, as opposed to FISH/cytogenetics which only tests from 50 to 200 cells. Given you say your 3mth results were not quite at <10% I assume it was pretty near that percentage? A good response at 3mths is considered to be at/< 35% Ph+ or at/< 10% BCR/ABL.
Try not to focus too much on achieving optimal goals outlined in ELNet Recommendations and/or NCCN Guidelines. Many of us have taken longer to reach these goals/milestones but have gone on to respond very well to TKI therapy and have reached the recommended goal eventually.
You may find it helpful to read our booklet about PCR testing - see below for a snippet from the booklet: Q-PCR testing
Qualitative PCR (NOTE: this kind of PCR test confirms whether you have or do not have the BCR/ABL gene and therefore have Ph+CML)
The polymerase chain reaction qualitative test is used to diagnose Ph+CML by confirming whether or not BCR-ABL1 gene transcripts (copies) are present in a blood and/or bone marrow sample. It can detect very small amounts of BCR-ABL1, even when the Philadelphia chromosome is not detected in bone marrow cells with cytogenetic testing.
FISH: Fluorescence in situ hybridization
A more sensitive method than cytogenetics, testing upwards of 50 to 200 cells. FISH uses probes labelled with fluorescent dyes which ‘light up’ the fused BCR-ABL1 gene sequence. Fluorescent probes are sections of single strands of DNA complementary to the specific portions of the DNA of interest, in this case, the ABL1 and BCR-ABL1 genes. When slides are examined using a special microscope, the genes that match the DNA probe appear as bright spots on a dark background. The test determines the percentage of cells in a sample containing the BCR-ABL1 gene. It can be used on either blood or bone marrow samples without the need to culture the cells, so results are available more quickly than with conventional cytogenetics.
Quantitative Reverse Transcriptase Polymerase Chain Reaction (QRT-PCR): What the test measures and its relationship to other tests.
At diagnosis, virtually every white cell in a blood or marrow sample will be leukaemic (Ph+) so the result should, in theory, be 100% Ph+.
However, because there are higher levels of Ph+ cells present at diagnosis, q-PCR testing is not accurate, which is why Ph positivity varies between 50% and 100%. This test may be used to establish a baseline value of Ph+ cells at diagnosis.
After the start of therapy, Q-PCR is used at specific time points after cytogenetic/FISH tests.
Once tests show that the Ph+ cell population has reduced to less than 10%, Q (quantitative) PCR testing can more accurately quantify the amount of residual disease left in the marrow.
The goal of TKI therapy is to reduce the abnormal BCR-ABL1 gene to a deep molecular level, preferably to at least 0.1% (MMR/MR3).
During the first 3, 6, 9 and 12 months of therapy, Ph+ cells should reduce significantly.
When the level of Ph+ cells falls below 1% Q-PCR testing is extremely accurate and will be used to monitor the stability of a molecular response.
Under ideal conditions, this test (quantitative PCR) can detect 1 Ph+ cell in every 100,000 cells, although more commonly it detects 1 Ph+ cell in every 10,000.
I hope this reassures you,
Sandy
