Measurable residual disease in chronic lymphocytic leukemia: expert review and consensus recommendations

Assessment of measurable residual disease (often referred to as "minimal residual disease") has emerged as a highly sensitive indicator of disease burden during and at the end of treatment and has been correlated with time-to-event outcomes in chronic lymphocytic leukemia. Undetectable-measurable residual disease status at the end of treatment demonstrated independent prognostic significance in chronic lymphocytic leukemia, correlating with favorable progression-free and overall survival with chemoimmunotherapy. Given its utility in evaluating depth of response, determining measurable residual disease status is now a focus of outcomes in chronic lymphocytic leukemia clinical trials. Increased adoption of measurable residual disease assessment calls for standards for nomenclature and outcomes data reporting. In addition, many basic questions have not been systematically addressed. Here, we present the work of an international, multidisciplinary, 174-member panel convened to identify critical questions on key issues pertaining to measurable residual disease in chronic lymphocytic leukemia, review evaluable data, develop unified answers in conjunction with local expert input, and provide recommendations for future studies. Recommendations are presented regarding methodology for measurable residual disease determination, assay requirements and in which tissue to assess measurable residual disease, timing and frequency of assessment, use of measurable residual disease in clinical practice versus clinical trials, and the future usefulness of measurable residual disease assessment. Nomenclature is also proposed. Adoption of these recommendations will work toward standardizing data acquisition and interpretation in future studies with new treatments with the ultimate objective of improving outcomes and curing chronic lymphocytic leukemia.

Single center retrospective analysis of BU-based conditioning regimens in allogeneic transplantation

We performed a single institution retrospective analysis of 114 patients treated with BU-based pretransplant conditioning regimens. Oral BU was administered to 76 patients (total dose 16 mg/kg or 8 mg/kg) and i.v. BU to 38 others (total dose 12.8 mg/kg or 6.4 mg/kg). Either CY (n=74) or fludarabine (n=40) was given in combination with BU. Median age was 35 years in the oral BU group and 48.5 years with i.v. BU (P<0.001). OS and PFS rates at 3-years post HSCT were not different in patients who received either i.v. or oral BU (OS: 41.3 vs 44.0% (P=0.981); PFS: 52.7 vs 54.7% (P=0.526), respectively). The i.v. BU, however, was associated with a significantly shorter time to engraftment (13.5 days vs 16 days, respectively; P<0.001). There were no significant differences in survival or 100-day mortality for patients who received either CY or fludarabine, in combination with BU. After adjustment for confounders, multivariate analysis showed that age of transplant (P=0.002), donor type (sibling or unrelated; P=0.003), GVHD (P<0.05) and route of administration (P=0.023) were significant risk factors for OS. The i.v. BU used in an older age group yielded equivalent survival compared with oral BU used in a younger population.