Since 2011, the Cell Therapy and Flow Cytometry Laboratory at the Royal Children’s Hospital (RCH) has been performing Minimal Residual Disease testing by flow cytometry. Approximately 110 new diagnostic B cell Acute Lymphoblastic Leukaemia (B-ALL) cases and 500 B-ALL assays are performed each year in the Flow Cytometry laboratory at the RCH. This testing has since proved to be a valuable prognostic indicator for patients that may have lingering disease.
However, since MRD testing began at RCH, there have been multiple new treatments aimed at targeting CD19 B cells. This includes Blinatumomab, a small molecule binding CD19 B cells and CD3 T cells and Chimeric Antigen Receptor T cell Therapy, a genetically modified cell directed against CD19 B cells. Although successful, these new therapies have an obfuscating effect in the identification of MRD as most B-ALL cases express CD19 and will use this marker in their gating strategy.
To combat this, a new assay based on the paper by Cherian et al1 with the addition of 2 informative markers, was designed to improve detection. This was especially important with cases that relapse with CD19 negative disease. Testing compared to current Children’s Oncology Group assay method was successful and proved to be a welcome addition to the current assay.