Prospective assessment of white matter integrity in adult stem cell transplant recipients

Hematopoietic stem cell transplantation (HSCT) is often used in the treatment of hematologic disorders. Although it can be curative, the pre-transplant conditioning regimen can be associated with neurotoxicity. In this prospective study, we examined white matter (WM) integrity with diffusion tensor imaging (DTI) and neuropsychological functioning before and one year after HSCT in twenty-two patients with hematologic disorders and ten healthy controls evaluated at similar intervals. Eighteen patients received conditioning treatment with high-dose (HD) chemotherapy, and four had full dose total body irradiation (fTBI) and HD chemotherapy prior to undergoing an allogeneic or autologous HSCT. The results showed a significant decrease in mean diffusivity (MD) and axial diffusivity (AD) in diffuse WM regions one year after HSCT (p-corrected <0.05) in the patient group compared to healthy controls. At baseline, patients treated with allogeneic HSCT had higher MD and AD in the left hemisphere WM than autologous HSCT patients (p-corrected <0.05). One year post-transplant, patients treated with allogeneic HSCT had lower fractional anisotropy (FA) and higher radial diffusivity (RD) in the right hemisphere and left frontal WM compared to patients treated with autologous HSCT (p-corrected <0.05).There were modest but significant correlations between MD values and cognitive test scores, and these were greatest for timed tests and in projection tracts. Patients showed a trend toward a decline in working memory, and had lower cognitive test scores than healthy controls at the one-year assessment. The findings suggest a relatively diffuse pattern of alterations in WM integrity in adult survivors of HSCT.