29 NCCN Guidelines for Patients ® : Chronic Myeloid Leukemia, 2018 4 Chronic phase Monitoring Monitoring It’s important to monitor the treatment response. This is done by testing a blood sample by QPCR. QPCR is a very good test for finding CML cells. It can find “a needle in a haystack.” Thus, it is the preferred testing method to see how treatment is working. QPCR-IS scores Across labs, different scales are used to measure and report QPCR test results. Thus, test results are not the same. It’s like how money differs across countries. For example, $1 in the United States is not equal to €1 in Europe. Results can also differ within the same lab. To solve this problem, the IS ( I nternational S cale) was made. The IS score is the percentage of cells with BCR-ABL1 that remain after treatment. See Figure 9 . This is called the molecular response. A conversion factor is used to convert your results to the IS. It’s like the exchange rate used to compare money from different countries. As a result, IS scores are consistent. Scores can also be compared between people and labs. The IS uses a standard baseline of BCR-ABL1 100%. A tenfold drop from baseline is called a log reduction. A 1-log reduction ( BCR-ABL1 10%) means there are 10 times fewer CML cells compared to baseline. A 2-log reduction ( BCR-ABL1 1%) means 100 times fewer cells. A 3-log reduction ( BCR-ABL1 0.1%) means 1,000 times fewer cells. A good lab can detect a 4.5-log reduction ( BCR-ABL1 0.0032%). Milestones For CML, treatment results are discussed in terms of milestones. These milestones are: EMR ( e arly m olecular r esponse) is defined as BCR-ABL1 ≤10% at 3 months and 6 months. It is a sign of how well treatment will work long term. CCyR ( c omplete cy togenetic r esponse) is the absence of the Philadelphia chromosome as measured by cytogenetics. A CCyR corresponds with BCR-ABL1 0.1% to BCR-ABL1 1%. It is often achieved within 12 months. MMR ( m ajor m olecular r esponse) is defined as BCR-ABL1 <0.1%. The goal is to reach this milestone between 12 and 18 months. Although not a milestone, another treatment result is a CMR ( c omplete m olecular r esponse). A CMR is when BCR-ABL1 can’t be detected. For this response, a lab that can detect at least a 4.5-log reduction is needed. Figure 9 QPCR-IS scores and milestones The IS score is the percentage of cells with BCR-ABL1 that remain after treatment. Milestones are based on the percentage and time since treatment started. Copyright © 2017 National Comprehensive Cancer Network ® (NCCN ® ). www.nccn.org Baseline 100% 10% 1-log reduction 1% 2-log reduction 0.1% 3-log reduction 0.0032% 4.5-log reduction EMR at 3 and 6 months CCyR by 12 months MMR by 18 months

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