Trimming the fat: obesity and hematopoietic cell transplantation.

Obesity, increasing worldwide, is common in patients undergoing hematopoietic cell transplantation (HCT). This complex physiological state may alter the outcome of cancer therapies by many mechanisms including direct effects on pathogenesis, host responses to disease and altered pharmacology of chemotherapy. Obesity has been associated with multiple adverse health outcomes. Reports of obese patients undergoing HCT are challenging to interpret because of the heterogeneity of obesity definitions, underlying diseases, graft sources and chemotherapy regimens employed. Compared with normal-weight patients, it appears that obese patients undergoing allogeneic HCT have a higher risk of non-relapse mortality and inferior survival whereas those receiving autologous HCT appear to have equivalent outcomes. These findings are also difficult to interpret because there is no consistent standard for calculating chemotherapy dose in this group and future studies on specific regimens in this population are urgently needed. Patients who have undergone bariatric surgery may be at risk for unexpected events because of impaired nutritional state and altered pharmacokinetics of oral drugs. We recommend that future studies utilize more consistent and biologically relevant definitions of obesity and that the pharmacokinetics and pharmacodynamics of specific conditioning regimens be studied. Until more evidence is available, a rationale is presented for dosing based on adjusted body weight. Moreover, recommendations are provided to guide future research efforts based on more definitive measurements of body fat and its distribution available through modern quantitative imaging techniques using dual energy X-ray absorptiometry or magnetic resonance imaging scanning.