HAT-PCR Enables Sensitive Quantification of Minimal Residual Disease in Chronic Lymphocytic Leukemia and Myeloma

The role of HAT-PCR (<b>H</b>igh <b>A</b>/<b>T</b> or <b>H</b>igh <b>A</b>nnealing <b>T</b>emperature-PCR) in the quantification of minimal residual disease (MRD) was investigated in chronic lymphocytic leukemia (CLL) and myeloma. The IGH gene sequence was determined by next-generation sequencing (NGS), either by the Lymphotrack kit or by preparing libraries using an in-house two-round PCR protocol which enabled successful sequencing in 37/37 CLL marrow samples and 34/35 myeloma marrow samples. MRD was quantified by HAT-PCR in 125 CLL marrow or blood samples from 36 patients, with 2 results being less than 10^-6 and in 63 myeloma marrow samples from 35 patients, with 10 results being less than 10^-6. Measurement of MRD in 113 pairs of CLL samples and 51 pairs of myeloma samples showed that HAT-PCR was significantly more sensitive than flow. Compared to marrow MRD, blood MRD was relatively high in CLL but very low or undetectable in myeloma. Flow-positive HAT-PCR negative samples were not seen in myeloma, although the literature review suggested that flow-positive NGS-negative myeloma samples are sometimes observed. The ability of HAT-PCR to quantify down to and below 10^-6 and the practical advantages of PCR suggest that HAT-PCR could be used widely for the quantification of MRD in lymphoid malignancy.