Research highlights ability of Bio-Rad's ddPCR in quantifying minimal residual disease

More than 30 abstracts presented at the 60th American Society of Hematology (ASH) Annual Meeting & Exposition in San Diego, December 1-4, featured research highlighting the ability of Bio-Rad's Droplet Digital PCR (ddPCR) to provide high sensitivity and accuracy in quantifying minimal residual disease (MRD) -- those remaining cancer cells after therapy that are associated with relapse -- in blood diseases such as leukemia.

One study described how ddPCR may be able to more accurately determine MRD than qPCR and therefore better determine which patients with childhood acute lymphoblastic leukemia are eligible for high-risk treatments. In another study, researchers found that the concentration of residual leukemic cells, determined by the QX200 Droplet Digital PCR System, was one of the risk factors that predicted relapse in patients with chronic myeloid leukemia who had discontinued therapy. In addition to these studies, below are highlights of other presentations that showed how ddPCR is used to measure MRD in patients with acute myeloid leukemia (AML).

ddPCR utilization in phase 1b trial in TP53-mutant MDS and AML

The following poster (abstract number 3091) was presented on Sunday, December 2.

Dr. David Sallman, a hematologic oncologist at the Moffitt Cancer Center in Tampa, Florida, presented results from a phase 1b clinical trial enabled by ddPCR. Dr. Sallman and his team tested the use of azacitidine, a chemotherapy drug, in combination with small-molecule drug APR-246 in patients with myelodysplastic syndromes (MDS) and AML with TP53 mutations. Data have previously shown that azacitidine alone leads to complete remission in 20 to 30% of patients with TP53 mutant MDS and AML. The results of this study showed that 82% of these patients achieved complete remission when APR-246 was added, representing a significant improvement over treatment with azacitidine alone.

The researchers used next-generation sequencing (NGS) and ddPCR to analyze the depth of remission by quantifying MRD. "In our trial we found that ddPCR was extremely effective at defining patient-specific depth of remission," Dr. Sallman said.

Phase 2 of the trial will continue to use ddPCR as one of the ways to determine the depth of remission, noted Dr. Sallman, adding that remission, as defined by ddPCR and high-sensitivity NGS assays, would also be evaluated as a predictor of outcomes in patients treated with APR-246 and azacitidine.

ddPCR helps predict remission in patients with AML

The following poster (abstract number 2139) was presented on Saturday, December 1.

Allogenic hematopoietic stem cell transplantation (HSCT) is one of the only curative therapies for hematologic malignancies such as AML. However, many patients relapse after transplantation.

Dr. Amanda Winters, MD, PhD, of the Department of Pediatrics at the University of Colorado and Children's Hospital Colorado, and her team evaluated the use of ddPCR for monitoring MRD to predict which patients might relapse after HSCT. While MRD has previously been shown to be highly predictive of relapse for patients after chemotherapy, few studies have evaluated its predictive ability in HSCT.

The team used single-mutation ddPCR assays to track 21 different AML-associated mutations in a 36-patient cohort. All patients selected for this retrospective study had received a bone marrow transplant and consented to the Tissue Bank protocol, making past marrow and peripheral blood samples available to researchers. The patients had also been identified as having at least one of the 21 mutations at diagnosis.

The research found that ddPCR-based molecular MRD assessment was predictive for relapse and survival post-HSCT for patients with AML. The presence of molecular MRD at the one-month point after transplant was significantly correlated with relapse and mortality. Based on these findings, Dr. Winters and her team believe monitoring AML-associated mutations with ddPCR after transplant could help physicians detect relapse earlier.​