Clonal gammopathies following alemtuzumab-based reduced intensity conditioning haematopoietic stem cell transplantation: association with chronic graft-versus-host disease and improved overall survival.

The presence of clonal gammopathies (CG) has been reported following both conventional myeloablative and autologous haematopoietic stem cell transplantation (HSCT). We monitored the occurrence of CG in a cohort of patients with myeloid malignancies receiving FBC (fludarabine-busulphan-alemtuzumab)-based reduced intensity conditioned (RIC) HSCT, and assessed its correlation with infections, graft-versus-host disease (GvHD) and survival. Serial serum protein electrophoresis was analysed in a total of 138 patients and CG were detected in 49 patients (36%). The predominant Ig isotype was IgG (82%). There was no difference in the incidence of viral infections between patient groups. However, patients with gammopathies were more likely to have had prior chronic GvHD (OR 2.7, 95% CI 1.3-5.5, P<0.001). On multivariate analysis, the only factors that were found to influence overall survival (OS) were presence of gammopathies, which was associated with an improved OS (OR 0.35 95% CI 0.14-0.86, P=0.02) as well as disease stage, patients with advanced disease having a higher risk of death (OR 2.20 95% CI 1.18-4.11, P=0.02). Disease stage was the only variable that influenced relapse incidence on multivariate analysis (OR 4.22 95% CI 1.82-9.78, P<0.01). Clonal gammopathies are a frequent but benign occurrence following alemtuzumab-based RIC HSCT, and their appearance may define a group of patients with a favourable overall outcome.