Isotype class switching after transplantation in multiple myeloma.

Switching of the paraprotein isotype or transient presence of oligoclonal bands detectable by serum immunofixation electrophoresis has been reported following not only transplantations, but also after intensive chemotherapy for leukemia. Retrospective analysis of 72 transplanted myeloma patients was carried out to determine the frequency and clinical significance of the appearance of abnormal proteins bands (APB) distinct from the original paraprotein. APB presence was observed in 31 patients (43%) already after the first autotransplant, the median interval from transplant was 2 months (range, 1 to 6 months). The most frequent occurrence of APB was observed after allogeneic transplantation. In the group of patients with APB presence more patients achieved complete remission (32.2% versus 17.1%), statistically significant differences were also established when we compared the percentage of surviving patients and overall survival, to the present date, among both groups of patients (p=0.03). All relapsed patients with previous isotype class switching had disease characterized by the same type of paraprotein as that detected at diagnosis. The development of APB is likely related to the recovery of impaired immunoglobulin production after transplantation. We confirmed favourable prognostic significance of this finding in transplanted myeloma patients.