Comorbidity indices in hematopoietic stem cell transplantation: a new report card

Comorbid conditions have not been studied systematically for impact upon patient outcome in the setting of hematopoietic stem cell transplantation (HSCT). Patients formerly excluded from myeloablative transplant due to comorbid illnesses now receive reduced-intensity conditioning regimens; hence, the incidence of comorbid conditions in HSCT recipients is expected to increase. Comorbid grading systems developed without regard for oncology patients have been applied in retrospective fashion to HSCT patients. Two commonly used scales (Charlson Comorbidity Index and the Adult Comorbidity Inventory-27) fail to include critical information: tumor and histologic type/stage, extent of prior treatment, donor stem cell source and cell type and preparative regimen. Further, data are reported in retrospective rather than prospective fashion. Despite limitations, however, such grading systems exhibit ease and utility for evaluation and may have predictive value for patient outcome. Modifying such approaches to include additional factors and appropriate weighting of components may enable an improved comparison of techniques and study results. These scoring systems may elucidate predictors of outcome and disease natural history and enhance statistical efficiency methods of HSCT. Refined scoring could be used effectively to assign patients to differing transplant conditioning regimens, that is, myeloablative vs reduced intensity. Prospective validation of such grading systems is encouraged.