Precision Medicine: Applying Cutting-Edge Technology to Patient Care
One of the challenges to monitor disease status in hematologic malignancies after a curative treatment such as transplant is the lack of a patient-specific and sensitive test. Standard methods using either mutliparameter flow cytometry or routine polymerase chain reaction (PCR) are usually non-specific and their ability to detect minimal residual disease (MRD) is limited. Developing a cost effective and universally applicable assay with tumor-specificity and high sensitivity to monitor MRD is a goal of the Stanford BMT immuno-monitoring team.
Taking advantage of high-throughput sequencing (HTS) technology, Drs. David Miklos and Wen-Kai Weng tested the possibility of using HTS of B-cell receptor (BCR) and T-cell receptor (TCR) gene rearrangement to monitor MRD after allogeneic transplant. In their work, the unique rearranged CDR3 sequences of BCR or TCR were identified by HTS from the diagnostic samples; either blood samples from CLL or ALL patients, or skin samples from patients with cutaneous T-cell lymphoma. Once the patient-specific unique CRD3 sequence (the cancer clonotype) was identified, HTS was used to monitor the frequency of the cancer clonotype in the blood or skin samples from individual patients at different time points after allogeneic transplant. Research from both Miklos’ and Weng’s teams showed that HTS can provide a patient-specific test with utmost sensitivity, which is at least 2 logs more sensitive than the routine BCR PCR or TCR PCR. In patients with CLL, the detection of MRD progression by HTS preceded the clinical relapse using standard diagnostics by 3-6 months. Once this finding is confirmed by a larger study, it will be reasonable to investigate whether early intervention in the cases of MRD progression can prevent clinical relapse. In patients with cutaneous T-cell lymphoma (mycosis fungoides and Sézary syndrome), molecular remission in both blood and skin compartments were found in around 50% of the patients after allogeneic transplant. It provided the possibility of a cure in these advance staged patients.
To push the envelope of the HTS technology, Dr. Everett Meyer used the change of TCR repertoire to predict the clinical response to therapy in patients who developed acute GVHD of the gastrointestinal tract. In his recent publication, he found a GVHD-associated TCR repertoire from the gut biopsy samples, that can be monitored in the subsequent blood samples from the same patient after GVHD therapy. The study showed that dissipation of the GVHD-associated TCR repertoire in the blood after therapy highly correlated with clinical response. From the preliminary analysis, this GVHD-associated TCR repertoire was patient-specific and was not shared between patients.
Bringing cutting-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.