Chimerism does not influence graft-versus-myeloma and graft-versus-host disease in reduced intensity setting

Chimerism analysis for clinicians: a review of the literature and worldwide practices

This review highlights literature pertinent to chimerism analysis in the context of hematopoietic cell transplantation (HCT). We also conducted a survey of testing practices of program members of CIBMTR worldwide. Questions included testing methods, time points, specimen type, cell lineage tested and testing indications. Recent literature suggests that detection of low level mixed chimerism has a clinical utility in predicting relapse. There is also increasing recognition of HLA loss relapse to potentially guide rescue decisions in cases of relapse. These developments coincide with wider access to high sensitivity next generation sequencing (NGS) in clinical laboratories. Our survey revealed a heterogeneity in practices as well as in findings and conclusions of published studies. Although the most commonly used method is STR, studies support more sensitive methods such as NGS, especially for predicting relapse. There is no conclusive evidence to support testing chimerism in BM over PB, particularly when using a high sensitivity testing method. Periodic monitoring of chimerism especially in diagnoses with a high risk of relapse is advantageous. Lineage specific chimerism is more sensitive than whole blood in predicting impending relapse. Further studies that critically assess how to utilize chimerism testing results will inform evidence based clinical management decisions.

Allogeneic Hematopoietic Cell Transplantation in Multiple Myeloma: Focus on Longitudinal Assessment of Donor Chimerism, Extramedullary Disease, and High-Risk Cytogenetic Features

Although generally not applied as first-line treatment of multiple myeloma, allogeneic hematopoietic cell transplantation (allo-SCT) can still be chosen as ultimate escalation approach in high-risk patients, preferentially within the framework of clinical trials. In this study, we investigated whether decreasing donor chimerism (DC) is predictive for relapse. In addition, we comprehensively determined the impact of several other disease- and treatment-related factors on outcome. One hundred fifty-five multiple myeloma patients whose DC status was followed serially by the short tandem repeat-based techniques at a single lab were included in this retrospective study. Outcome variables were studied in univariate and multivariable analyses. Available were 2.324 DC samples (median, 12 per patient). Loss of full DC was associated with shorter progression-free survival (PFS) (HR, 1.7; 95% CI, 1.1 to 2.6) but did not impact overall survival. Two-thirds of patients with International Myeloma Working Group-defined relapses still displayed a full DC in peripheral blood or bone marrow. Extramedullary manifestations were observed in 33% of patients, accounting for the discrepancy between DC analysis and the actual disease status. In multivariable analysis, the 2 most relevant variables for an unfavorable PFS were progressive disease before allo-SCT (HR, 3.0; 95% CI, 1.5 to 5.9) and allo-SCT at least the second relapse (HR, 2.8; 95% CI, 1.5 to 4.9), whereas for overall survival progressive disease or partial response before allo-SCT had the strongest negative effects (HR, 4.2; 95% CI, 1.9 to 9, and HR, 2.0; 95% CI, 1.0 to 3.8, respectively). Adverse cytogenetics such as del17p, t(4,14) or amp(1q21) were not associated with shorter survival after allo-SCT. Extensive DC sampling beyond robust engraftment does not appear to provide additional information helpful for disease management in most patients and is challenged by a significant incidence of extramedullary disease. In our series, allo-SCT overcame unfavorable cytogenetics.

Donor chimerism early after reduced-intensity conditioning hematopoietic stem cell transplantation predicts relapse and survival

The impact of early donor cell chimerism on outcomes of T cell-replete reduced-intensity conditioning (RIC) hematopoietic stem cell transplantation (HSCT) is ill defined. We evaluated day 30 (D30) and 100 (D100) total donor cell chimerism after RIC HSCT undertaken between 2002 and 2010 at our institution, excluding patients who died or relapsed before D30. When available, donor T cell chimerism was also assessed. The primary outcome was overall survival (OS). Secondary outcomes included progression-free survival (PFS), relapse, and nonrelapse mortality (NRM). We evaluated 688 patients with hematologic malignancies (48% myeloid and 52% lymphoid) and a median age of 57 years (range, 18 to 74) undergoing RIC HSCT with T cell-replete donor grafts (97% peripheral blood; 92% HLA-matched), with a median follow-up of 58.2 months (range, 12.6 to 120.7). In multivariable analysis, total donor cell and T cell chimerism at D30 and D100 each predicted RIC HSCT outcomes, with D100 total donor cell chimerism most predictive. D100 total donor cell chimerism <90% was associated with increased relapse (hazard ratio [HR], 2.54; 95% confidence interval [CI], 1.83 to 3.51; P < .0001), impaired PFS (HR, 2.01; 95% CI, 1.53 to 2.65; P < .0001), and worse OS (HR, 1.50; 95% CI, 1.11 to 2.04, P = .009), but not with NRM (HR, .76; 95% CI, .44 to 2.27; P = .33). There was no additional utility of incorporating sustained D30 to D100 total donor cell chimerism or T cell chimerism. Low donor chimerism early after RIC HSCT is an independent risk factor for relapse and impaired survival. Donor chimerism assessment early after RIC HSCT can prognosticate for long-term outcomes and help identify high-risk patient cohorts who may benefit from additional therapeutic interventions.

Therapy of relapsed and refractory multiple myeloma

Despite considerable improvements in first line treatment still the majority of patients experience relapse of multiple myeloma. Treatment decisions for relapse or refractory multiple myeloma should be based on a clinical decision path taking response and adverse events to previous therapy, myeloma specific complications and organ dysfunctions, overall clinical condition, age, cytogenetic information and prognostic factors into account. Bortezomib, thalidomide and lenalidomide have improved the therapeutic armentarium for patients with refractory or relapsed disease and are often used in combination with dexamethasone or chemotherapeutic agents. Combination therapies of novel agents in drug combination regimen are currently under investigation as well. For patients with a disease free survival of 12 month or longer after initial single or tandem high dose therapy and autologous stem cell transplantation (ASCT) repeat of high dose therapy with melphalan and ASCT should be considered in case of relapse. Radiotherapy and osteoplastic procedures can be used as adjunct to systemic therapy to treat local complications in particular vertebral pain caused by osteolytic bone disease. Cytogenetic tests, molecular techniques as gene expression profiling and other diagnostic will lead to a more individualized therapy. The integration of novel compounds into established regimen will be a major challenge for future clinical studies.

Blood group chimerism

PURPOSE OF REVIEW

With improved methods for detecting chimeras and growing numbers of stem cell transplantations, blood group and other forms of chimerism are observed with increasing frequency. This review will focus on the state of science and new insights into the multifaceted subject of blood group chimerism.

RECENT FINDINGS

Recognition that the immune system tolerates chimeric cells under certain conditions has led to efforts to elucidate related immune-modulating processes. The chimeric state following transplantation of hematopoietic stem cells, as well as after solid organ transplantation, is of special interest. Also, chimerism is considered to be a potential trigger for certain autoimmune diseases. Natural chimerism is more frequent than previously recognized. Using improved laboratory techniques, investigators can often trace chimeric tissues to their origin. New therapeutic strategies have been applied after stem cell transplantation depending on the chimeric state. Also, recent research has resulted in methods for determining chimerism in maternal peripheral blood that reflect fetal blood type and certain congenital diseases.

SUMMARY

The subject of human chimerism has evolved from a curiosity of nature to an important field of research and, potentially, holds the key to advancing our understanding of the fundamental mechanisms of immune tolerance.