Avoidance of Post-Thaw Wash Prior to Transplantation of Plasma Depleted Cord Blood (PD CB) Is Associated with Improved Engraftment & Decreased Severity of Chronic GvHD (cGvHD) without Increased Relapse.

Post-thaw washing of frozen CB prior to transplantation is widely practiced to remove DMSO, red cell debris and free hemoglobin, however, washing a red cell containing product may result in cell loss. We analyzed outcomes of engraftment, survival, relapse and GvHD in 299 patients transplanted with plasma depleted but not red cell reduced (PD) CB where 154 were washed (W) and 145 were directly infused - (non-washed or NW). 207 (69%) of 299 patients had malignant diagnosis. The two groups were comparable for patient, disease and graft characteristics except for a higher % of Asian patients in the NW group in contrast to a higher % of Caucasian/Hispanic patients, higher % of US transplant centers (TC) and higher number of malignant diagnoses for the W group. Nucleated cell recovery after thawing, as reported by TC, was higher for NW (median 85% vs. 79%, p=0.003). The NW group had higher cumulative incidences of and faster neutrophil (ANC500) and platelet engraftment (Plt 20K and 50K) than the W group. No difference was seen for acute GvHD (aGvHD); however, the NW group had significantly lower rates of extensive (Ext) cGvHD and higher rates of limited (Ltd) cGvHD (p=0.0005 and <0.0001). Relapse rates were similar between W and NW. Multivariate analysis and matched pair analysis between W versus NW confirm these observations. In univariate analysis, overall survival (OS) and disease-free survival (DFS) were significantly higher for the NW group. This retrospective analysis represents the largest series comparing different thaw methods for PD CB and is the first to demonstrate a potential association of no post-thaw wash with significant decrease in extensive cGvHD rate without concomitant increase in relapse rate. These improvements may contribute to the apparently better survival for the NW group. Prospective trials which may include infusion of wash supernatants into patients are necessary to confirm and better understand these observations.