The Impact of Clinical and Morphometric Parameters on Hematopoietic Engraftment Following High-Dose Chemotherapy and Autologous Stem Cell Transplantation in Germ Cell Tumors

Background and Objectives: Relapsed or refractory germ cell tumors are commonly treated with HDCT/ASCT, but robust predictors of hematopoietic recovery are limited. Quantitative CT-based metrics of body composition are readily available, but their prognostic value for post-transplant engraftment remains uncertain. We investigated whether muscle and fat indices derived from routine CT scans are associated with the pace of hematologic recovery after HDCT/ASCT. Materials and Methods: This retrospective study analyzed a single-center cohort (n = 43) with relapsed/refractory GCT undergoing HDCT/ASCT. CT within 6 months pre-HDCT/ASCT was analyzed at L3 to derive the Skeletal muscle index, Psoas muscle index, Subcutaneous fat area, Visceral fat area, Total fat area, Visceral-to-subcutaneous fat area ratio. Primary endpoint: The engraftment time post-ASCT. Spearman’s ρ was used for univariable associations; multivariable linear regressions were adjusted for age, Hb, weight, and BSA to evaluate the independent effects. The significance was set at p < 0.05. Results: The median hematologic engraftment duration was 12.0 days, and the engraftment duration was positively correlated with age and negatively with hemoglobin. According to the multivariable analysis, older age and lower hemoglobin independently predicted longer engraftment; body weight and BSA were not significant. Among the morphometrics, only the VFA/SFA ratio was associated with delayed engraftment. The SMI, PMI, and TFA were not significant. As expected, after HDCT, grade 4 neutropenia and thrombocytopenia occurred in all patients. Conclusions: In relapsed/refractory GCT treated with HDCT/ASCT, older age and lower post-transplant hemoglobin independently predicted a prolonged engraftment. Beyond traditional muscle/fat areas, a higher VFA/SFA ratio—reflecting visceral adiposity—is also associated with delayed recovery, suggesting that fat distribution may influence hematopoietic regeneration. These variables may support pre-transplant risk stratification and individualized supportive care.