PMC6745955_01
Biological data during the clinical course of the patient. BCR-ABL1 fusion transcript ratio was of 36.9% at diagnosis of CML while CALR allele burden was of 0.8% and was only detectable using digital PCR. At 3 months, BCR-ABL1 ratio decreased to 0.96% and CALR mutation allele burden increase to 27%. During the follow up, CML achieved a BCR-ABL1 molecular response MR4 at 1 year and MR4.5 at 15 months. The CALR mutation remained stable between 20% and 30% of allele burden.
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F1
After 3 months, a reincrease of platelets count was observed (1022 109/L) despite an optimal molecular response to imatinib with a ratio BCRL-ABL1/ABL1 of 0.96% (Fig. 1). The CALR allele burden remained stable during the follow-up around 25% to 30% (Fig. 1).
Molecular screening for CALR mutation. Screening for CALR mutation was performed by fragment analysis at diagnosis of CML (panel A), and 3 months later when the thrombocytosis appeared (panel B). Digital PCR at the time of diagnosis of CML was able to detect the CALR type 1 mutation with a VAF of 0.8% (panel C). VAF = variant allele frequency, WT = wild-type allele.
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F2
ThermoFisher, Waltham, USA), a more sensitive technology that allow detection up to 0.01% of allele burden. The type 1 CALR mutation was detected with 0.8% of allele burden (Fig. 2).