Droplet digital PCR for BCR/ABL(P210) detection of chronic myeloid leukemia: A high sensitive method of the minimal residual disease and disease progression.

This study intended to establish a droplet digital PCR (dd-PCR) for monitoring minimal residual disease (MRD) in patients with BCR/ABL (P210)-positive chronic myeloid leukemia (CML), thereby achieving deep-level monitoring of tumor load and determining the efficacy for guided clinically individualized treatment. Using dd-PCR and RT-qPCR, two cell suspensions were obtained from K562 cells and normal peripheral blood mononuclear cells by gradient dilution and were measured at the cellular level. At peripheral blood (PB) level, 61 cases with CML-chronic phase (CML-CP) were obtained after tyrosine kinase inhibitor (TKI) treatment and regular follow-ups. By RT-qPCR, BCR/ABL (P210) fusion gene was undetectable in PB after three successive analyses, which were performed once every 3 months. At the same time, dd-PCR was performed simultaneously with the last equal amount of cDNA. Ten CML patients with MR4.5 were followed up by the two methods. At the cellular level, consistency of results of dd-PCR and RT-qPCR reached R2  ≥ 0.99, with conversion equation of Y = 33.148X1.222 (Y: dd-PCR results; X: RT-qPCR results). In the dd-PCR test, 11 of the 61 patients with CML (18.03%) tested positive and showed statistically significant difference (P < .01). In the follow-up of 10 CML patients who were in MR4.5. All patients were loss of MR4.0, and 4 were tested positive by dd-PCR 3 months earlier than by RT-qPCR. In contrast with RT-qPCR, dd-PCR is more sensitive, thus enabling accurate conversion of dd-PCR results into internationally standard RT-qPCR results by conversion equation, to achieve a deeper molecular biology-based stratification of BCR/ABL(P210) MRD. It has some reference value to monitor disease progression in clinic.

Wang WJ ，Zheng CF ，Liu Z ，Tan YH ，Chen XH ，Zhao BL ，Li GX ，Xu ZF ，Ren FG ，Zhang YF ，Chang JM ，Wang HW ... -  《-》

Monitoring Treatment-Free Remission by Droplet Digital PCR in CML Patients with Deep Molecular Response to Tyrosine Kinase Inhibitor: An Analysis Based on Real-World Data.

Treatment-free remission (TFR) is emerging as a new therapy goal for chronic myeloid leukemia (CML) patients in the tyrosine kinase inhibitors (TKI) era. Data indicates the unfavorable success rate of TFR. This study aimed to compare and evaluate the clinical value of dd-PCR in predicting relapse in CML patients entering TFR. Using dd-PCR and RT-qPCR technology, dynamic BCR/ABL transcripts were detected in 13 CML patients who discontinued TKI treatment after sustaining undetectable BCR-ABL levels for a median time of 25 months. The results showed that in 13 patients, only 2 cases (22.2%) of 9 patients who executed planned discontinuation achieved TFR within 12 months. In the first 6 months, the detection rate of BCR/ABL transcripts by dd-PCR was higher than that by RT-qPCR and the two methods kept a positive correlation (r=0.9651, P=0.0349). Meanwhile, the time of detectable BCR/ABL by dd-PCR were significantly shorter (P<0.05), which was an average of 2.98 months earlier than RT-qPCR. The total TKI therapy and MR4.5 duration time related with TFR were longer in patients with intermediate or high Sokal risk scores (p<0.05). The dd-PCR could be more sensitive than RT-qPCR for monitoring BCR/ABL transcripts of CML patients with deep molecular response to TKI. The technique can be used as a preferred method to detect the transcripts in the first 6 months after TKI cessation.

Zhu G ，Yang Y ，Wang H ，Xie J ，Hu J ，Guo W ，Zhang L ，Liu Z ，Chen X ，Chang J ，Xu J ，Tan Y ... -  《-》

Sensitive detection and quantification of minimal residual disease in chronic myeloid leukaemia using nested quantitative PCR for BCR-ABL DNA.

Increasing numbers of patients with chronic myeloid leukaemia (CML) treated with tyrosine kinase inhibitors achieve undetectable levels of BCR-ABL mRNA using sensitive quantitative real-time reverse transcriptase PCR (RT-qPCR) methods and a method to measure minimal residual disease (MRD) in patients with low levels could be of value. Following isolation and sequencing of the patient-specific BCR-ABL breakpoint, a DNA-based nested qPCR assay was established, and MRD was measured by this method and one-round RT-qPCR in 38 samples from 24 patients with CML. Mixing experiments using patient DNA in normal DNA indicated that DNA qPCR could detect BCR-ABL sequences at a limit of approximately 10⁻⁶. In 22 samples in which MRD was detectable by both methods, comparison of the results of DNA qPCR with the results obtained on the same sample by RT-qPCR showed good correlation. In another 16 samples, BCR-ABL mRNA was not detectable by RT-qPCR. In 8 of the 16 samples, BCR-ABL DNA was detected at levels ranging from 1.1 × 10⁻⁵ up to 2.8 × 10⁻⁴ and in the remaining eight samples BCR-ABL was not detected by either method. In one patient, who had stopped imatinib, an almost 1000-fold rise in MRD, to 5.2 × 10⁻⁴ was observed in sequential samples. Nested DNA qPCR was more sensitive than one-round RT-qPCR and could be used for the monitoring of patients with CML with very low levels of MRD.

Bartley PA ，Ross DM ，Latham S ，Martin-Harris MH ，Budgen B ，Wilczek V ，Branford S ，Hughes TP ，Morley AA ... -  《-》

Molecular analysis of lineage-specific chimerism and minimal residual disease by RT-PCR of p210(BCR-ABL) and p190(BCR-ABL) after allogeneic bone marrow transplantation for chronic myeloid leukemia: increasing mixed myeloid chimerism and p190(BCR-ABL) dete

Serrano J ，Roman J ，Sanchez J ，Jimenez A ，Castillejo JA ，Herrera C ，Gonzalez MG ，Reina L ，Rodriguez MC ，Alvarez MA ，Maldonado J ，Torres A ... -  《BLOOD》

RT-qPCR and RT-Digital PCR: A Comparison of Different Platforms for the Evaluation of Residual Disease in Chronic Myeloid Leukemia.

Tyrosine kinase inhibitors (TKIs) are the cornerstone of successful clinical management of patients with chronic myeloid leukemia (CML). Quantitative monitoring of the percentage of the fusion transcript BCR-ABL1 (breakpoint cluster region-c-abl oncogene 1, non-receptor tyrosine kinase) BCR-ABL1IS (%BCR-ABL1IS) by reverse transcription-quantitative PCR (RT-qPCR) is the gold standard strategy for evaluating patient response to TKIs and classification into prognostic subgroups. However, this approach can be challenging to perform in a reproducible manner. Reverse-transcription digital PCR (RT-dPCR) is an adaptation of this method that could provide the robust and standardized workflow needed for truly standardized patient stratification. BCR-ABL1 and ABL1 transcript copy numbers were quantified in a total of 102 samples; 70 CML patients undergoing TKI therapy and 32 non-CML individuals. 3 commercially available digital PCR platforms (QS3D, QX200 and Raindrop) were compared with the platform routinely used in the clinic for RT-qPCR using the EAC (Europe Against Cancer) assay. Measurements on all instruments correlated well when the %BCR-ABL1IS was ≥0.1%. In patients with residual disease below this level, greater variations were measured both within and between instruments limiting comparable performance to a 4 log dynamic range. RT-dPCR was able to quantify low-level BCR-ABL1 transcript copies but was unable to improve sensitivity below the level of detection achieved by RT-qPCR. However, RT-dPCR was able to perform these sensitive measurements without use of a calibration curve. Adaptions to the protocol to increase the amount of RNA measured are likely to be necessary to improve the analytical sensitivity of BCR-ABL testing on a dPCR platform.

Alikian M ，Whale AS ，Akiki S ，Piechocki K ，Torrado C ，Myint T ，Cowen S ，Griffiths M ，Reid AG ，Apperley J ，White H ，Huggett JF ，Foroni L ... -  《-》