Contributions
Abstract: PB1957
Type: Publication Only
Background
Chronic myeloid leukemia (CML) is caused by a reciprocal translocation between chromosome 9 and 22 forming an oncogenic BCR-ABL1 fusion gene. A BCR-ABL1 Tyrosine kinase inhibitor (TKI) is a therapeutic agent in patients with CML. Although highly potent TKIs have been developed for deeper molecular response, about 50 % of sustained DMR achieved CML patients relapse after TKI cessation. To predict the suitable time point for TKI treatment cessation, highly sensitive and specific molecular real-time quantitative polymerase chain reaction (RQ-PCR) is required to monitor minimal residual disease (MRD) levels.
Aims
In this study, we aimed to evaluate the newly developed RQ-PCR as an additional study of “The Delightedly Overcome CML Expert Stop TKI (DOMEST) trial” conducted by the DOMEST group in Japan.
Methods
In the DOMEST study, after stopping imatinib DMR was assessed by RQ-PCR in a central laboratory (BML, Tokyo, Japan). For this analysis we used residual total RNAs from 102 patient samples of DOMEST trial, which recruited CML patients in chronic phase received imatinib therapy, reduced BCR-ABL1 levels to undetectable levels (MR4.0) by transcription-mediated amplification (TMA), reverse transcriptase-polymerase chain reaction or RQ-PCR for over 2 years. The median age of the patients was 62 years (27-88). The percentage of the patients who had low Sokal risk scores was 57 of 102 cases (56%) and the median duration of imatinib treatment was 99.5 months (13.0-160.0).
Results
BCR-ABL1 negativity has been confirmed by the central laboratory RQ-PCR assay at the starting time point of the DOMEST study (n=102). In 6 of these samples (6 %) the new RQ-PCR assay detected BCR-ABL1 transcripts which were confirmed by the sequencing analysis.
During the MRD monitoring after imatinib cessation, the new RQ-PCR assay detected BCR-ABL1 positivities at the same timing with the central laboratory RQ-PCR in 15 of 102 cases (15%). Correlation of IS % BCR-ABL1/ABL1 between the new RQ-PCR and the central laboratory RQ-PCR assays showed a strong correlation (r = 0.74, P = 0.003). The new RQ-PCR assay detected MRD in 21 cases (21%) at the earlier timing than the central laboratory RQ-PCR assay. We further examined BCR-ABL1 mRNA levels in these 21 samples by a commercially available ODK-1201 RQ-PCR assay kit (Otsuka Pharmaceutical Co., Tokyo, Japan), which detected the low level of BCR-ABL1 mRNA in 14 samples (74%) and negative in 5 samples (26%) with 2 samples of not available due to the insufficient amount. No sample with BCR-ABL1 positive by the central laboratory RQ-PCR assay and negative by the new RQ-PCR assay was observed.
Conclusion
The newly developed RQ-PCR assay has been shown to be more efficient for monitoring MRD in TKI-treated CML comparing the conventional PCR based assays. Further clinical studies of monitoring MRD in TKI-treated CML are required.
Session topic: 8. Chronic myeloid leukemia - Clinical
Keyword(s): BCR-ABL, Chronic myeloid leukemia, MRD, RQ-PCR
Abstract: PB1957
Type: Publication Only
Background
Chronic myeloid leukemia (CML) is caused by a reciprocal translocation between chromosome 9 and 22 forming an oncogenic BCR-ABL1 fusion gene. A BCR-ABL1 Tyrosine kinase inhibitor (TKI) is a therapeutic agent in patients with CML. Although highly potent TKIs have been developed for deeper molecular response, about 50 % of sustained DMR achieved CML patients relapse after TKI cessation. To predict the suitable time point for TKI treatment cessation, highly sensitive and specific molecular real-time quantitative polymerase chain reaction (RQ-PCR) is required to monitor minimal residual disease (MRD) levels.
Aims
In this study, we aimed to evaluate the newly developed RQ-PCR as an additional study of “The Delightedly Overcome CML Expert Stop TKI (DOMEST) trial” conducted by the DOMEST group in Japan.
Methods
In the DOMEST study, after stopping imatinib DMR was assessed by RQ-PCR in a central laboratory (BML, Tokyo, Japan). For this analysis we used residual total RNAs from 102 patient samples of DOMEST trial, which recruited CML patients in chronic phase received imatinib therapy, reduced BCR-ABL1 levels to undetectable levels (MR4.0) by transcription-mediated amplification (TMA), reverse transcriptase-polymerase chain reaction or RQ-PCR for over 2 years. The median age of the patients was 62 years (27-88). The percentage of the patients who had low Sokal risk scores was 57 of 102 cases (56%) and the median duration of imatinib treatment was 99.5 months (13.0-160.0).
Results
BCR-ABL1 negativity has been confirmed by the central laboratory RQ-PCR assay at the starting time point of the DOMEST study (n=102). In 6 of these samples (6 %) the new RQ-PCR assay detected BCR-ABL1 transcripts which were confirmed by the sequencing analysis.
During the MRD monitoring after imatinib cessation, the new RQ-PCR assay detected BCR-ABL1 positivities at the same timing with the central laboratory RQ-PCR in 15 of 102 cases (15%). Correlation of IS % BCR-ABL1/ABL1 between the new RQ-PCR and the central laboratory RQ-PCR assays showed a strong correlation (r = 0.74, P = 0.003). The new RQ-PCR assay detected MRD in 21 cases (21%) at the earlier timing than the central laboratory RQ-PCR assay. We further examined BCR-ABL1 mRNA levels in these 21 samples by a commercially available ODK-1201 RQ-PCR assay kit (Otsuka Pharmaceutical Co., Tokyo, Japan), which detected the low level of BCR-ABL1 mRNA in 14 samples (74%) and negative in 5 samples (26%) with 2 samples of not available due to the insufficient amount. No sample with BCR-ABL1 positive by the central laboratory RQ-PCR assay and negative by the new RQ-PCR assay was observed.
Conclusion
The newly developed RQ-PCR assay has been shown to be more efficient for monitoring MRD in TKI-treated CML comparing the conventional PCR based assays. Further clinical studies of monitoring MRD in TKI-treated CML are required.
Session topic: 8. Chronic myeloid leukemia - Clinical
Keyword(s): BCR-ABL, Chronic myeloid leukemia, MRD, RQ-PCR