Digital PCR improves the quantitation of DMR and the selection of CML candidates to TKIs discontinuation

Cancer Med. 2019 May;8(5):2041-2055. doi: 10.1002/cam4.2087. Epub 2019 Apr 4.

Abstract

Treatment-free remission (TFR) by tyrosine kinase inhibitors (TKI) discontinuation in patients with deep molecular response (DMR) is a paramount goal in the current chronic myeloid leukemia (CML) therapeutic strategy. The best DMR level by real-time quantitative PCR (RT-qPCR) for TKI discontinuation is still a matter of debate. To compare the accuracy of digital PCR (dPCR) and RT-qPCR for BCR-ABL1 transcript levels detection, 142 CML patients were monitored for a median time of 24 months. Digital PCR detected BCR-ABL1 transcripts in the RT-qPCR undetectable cases. The dPCR analysis of the samples, grouped by the MR classes, revealed a significant difference between MR4.0 and MR4.5 (P = 0.0104) or MR5.0 (P = 0.0032). The clinical and hematological characteristics of the patients grouped according to DMR classes (MR4.0 vs MR4.5-5.0 ) were superimposable. Conversely, patients with dPCR values <0.468 BCR-ABL1 copies/µL (as we previously described) showed a longer DMR duration (P = 0.0220) and mainly belonged to MR4.5-5.0 (P = 0.0442) classes compared to patients with higher dPCR values. Among the 142 patients, 111 (78%) discontinued the TKI treatment; among the 111 patients, 24 (22%) lost the MR3.0 or MR4.0 . RT-qPCR was not able to discriminate patients with higher risk of MR loss after discontinuation (P = 0.8100). On the contrary, according to dPCR, 12/25 (48%) patients with BCR-ABL1 values ≥0.468 and 12/86 (14%) patients with BCR-ABL1 values <0.468 lost DMR in this cohort, respectively (P = 0.0003). Treatment-free remission of patients who discontinued TKI with a dPCR <0.468 was significantly higher compared to patients with dPCR ≥ 0.468 (TFR at 2 years 83% vs 52% P = 0.0017, respectively). In conclusion, dPCR resulted in an improved recognition of stable DMR and of candidates to TKI discontinuation.

Keywords: chronic myeloid leukemia; digital PCR (dPCR); minimal residual disease (MRD) monitoring; treatment-free remission (TFR); tyrosine kinase inhibitors (TKI) discontinuation.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Cohort Studies
  • Female
  • Fusion Proteins, bcr-abl / genetics*
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / drug therapy*
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / genetics
  • Male
  • Middle Aged
  • Neoplasm, Residual / diagnosis*
  • Neoplasm, Residual / genetics
  • Polymerase Chain Reaction / methods*
  • Protein Kinase Inhibitors / therapeutic use*
  • Sensitivity and Specificity
  • Treatment Outcome
  • Young Adult

Substances

  • Protein Kinase Inhibitors
  • Fusion Proteins, bcr-abl