Pilot Evaluation of a Microfluidic Assay to Detect Minimal Residual Disease and Predict Relapse in AML Patients

An unmet need in the treatment of AML is earlier detection of potential relapse by monitoring MRD. The hope is that if clinicians can pinpoint when a patient's MRD starts towards a rapid expansion to relapse, preemptive therapies can be instituted earlier with the hope of eliciting improved outcomes. Current methods fall short of the ability to properly monitor MRD in individual patients. An ideal MRD assay would be easy to conduct, sensitive to low MRD levels and suitable for frequent analysis. A significant challenge for achieving this in AML is that unlike other leukemias, AML's interpatient heterogeneity is immense; and there is no characteristic genetic mutation or aberrant protein expression pattern for AML patients , thus hindering the broad applicability of polymerase chain reaction (PCR), fluorescence in-situ hypbridization (FISH) or multi-parameter flow cytometry (MFC) testing for MRD. Furthermore, AML relapse is rapid and it's been calculated that 42 day sampling intervals would be a minimum frequency needed to predict 75% of relapses during follow up after chemotherapy or SCT.

The microfluidics assay being evaluated in this study is relatively inexpensive, broadly applicable, as it identifies almost all (>90%) of AML cells, and easy to use. The microfluidic chip device is constructed with antibodies immobilized within the chip that can detect cell surface antigens commonly expressed on leukemic cells (ie, CD33, CD34, CD117, and CD123) directly in the peripheral blood without requiring preprocessing. The captured cells are then exposed to fluorescent antibodies targeting surface proteins that are aberrantly expressed on AML blasts (eg CD7, CD56 etc.), and fluorescence microscopy is used to identify captured cells that express an aberrant surface protein. The investigators have already completed a pilot study using this technology to monitor 5 AML patients after SCT. Because this assay required peripheral blood and not a bone marrow biopsy, 39 microfluidic tests could be carried out compared to only 8 PCR, MFC, FISH, and/or microscopy tests. Moreover, the frequent testing allowed us to observe signs of impending relapse earlier than the bone marrow biopsy-based test. The investigators plan to build on our findings in this trial and test the applicability of using the microfluidic assay for early signs of AML relapse. If successful, the microfluidic chip assay could be employed for serial MRD evaluations both in the post-SCT setting and in patients with AML undergoing conventional chemotherapy while providing a venue for the detailed management of a particular patient's AML including response to therapy and risk for disease recurrence.