In order to monitor disease after a curative treatment such as allogeneic transplant, pioneer works from Drs. David Miklos and Wen-Kai Weng have established the utility of high-throughput sequencing (HTS) of either B-cell receptor (BCR) or T-cell receptor (TCR) in monitoring minimal residual disease (MRD). Once the unique rearranged CDR3 sequences of these receptor (the cancer clonotype) were identified, these patient-specific cancer clonotype(s) were used to measure paNent’s disease in a highly-specific, sensitive and quantitative manner using HTS. This new way to monitor MRD clearly outperforms the routine polymerase chain reaction (PCR) or multiparameter flow cytometry, and has replaced them in daily clinical practice at Stanford Hospital and Clinics.

This new disease monitoring tool using HTS has provided two ways to affect the clinical practice. First, given the utmost patient specificity and sensiyivity, it can be used to predict clinical outcome after allogeneic transplantation. In one such example, HTS was used to measure the patient-specific TCR sequences in patients with cutaneous T-cell lymphoma (mycosis fungoides and Sezary syndrome) after a non-myeloablative allogeneic transplant. Approximately 50% of the patients achieved molecular remission in both skin and blood compartments after allogeneic transplant while the other 50% had persistent MRD detected by HTS. Patients who achieved molecular remission had less chance of disease relapse than those who had detectable MRD (13% chance versus 92% chance of relapse). Even in patients who were in complete clinical remission (no detectable disease by physical examination, flow cytometry, imaging study), persistent MRD detected by HTS translated to a much higher chance of eventual disease relapse, compared to achieving molecular remission (84% chance versus 17% chance of relapse).

Second, HTS can be used to determine the degree of disease progression at the molecular level that requires intervention to prevent the eventual clinical relapse. To realize this aspect of the clinical utility of HTS, Dr. Lori Muffly has started a longitudinal study to monitor MRD status with HTS in patients with acute lymphoblastic leukemia (ALL) who receive either standard chemotherapy or transplant. In this prospective study, blood and bone marrow samples will be collected routinely for multiparameter flow cytometry and MRD determination after therapies. This large scale study will provide a definite data on the advantage of HTS compared to the flow cytometry, and on the clinical significance of MRD determined by HTS after therapies. Most importantly, it will help to shed light on whether intervenNon(s) based on MRD status will have a positive clinical impact on this patient population.

Bringing cuttng-edge technology to daily clinical patient care has been one of the research hallmarks of the Stanford BMT program. In this example, HTS provides an opportunity to care for our patients in a patient-specific manner that we call Precision Medicine.