Oligoclonal bands and immunoglobulin isotype switch during monitoring of patients with multiple myeloma and autologous hematopoietic cell transplantation: a 16-year experience.

Background: Over the last 20 years, high dose therapy followed by hemopoietic stem cell transplantation has been employed in patients with multiple myeloma (MM). During 16 years of follow-up, the degree of tumor response and survival in 238 patients with autologous stem cell transplantation (ASCT) and changes in the serum protein electrophoretic pattern were analyzed.

Methods: Agarose gel electrophoresis with densitometric analysis and immunofixation were performed to evaluate serum monoclonal protein. IgM, IgA, IgG and beta(2)-microglobulin (beta2M) were quantitated. Urine protein electrophoresis with IF was performed on cellulose acetate gel using colloidal silver staining without concentrating.

Results: After 34 months of follow-up (range 1-160 months), eight patients (3.4%) showed a distinct monoclonal protein band that was different from their original isotype switch. This was observed to be a transient phenomenon (22.2 months). Thirty-seven patients (15.5%) developed oligoclonal bands (OB) between the first and the twentieth month after ASCT (mean 4.4 months), which persisted for 7.9 months (1-36 months). The mean overall survival time was statistically different (p<0.05) between the group with OB and the group without them. Mean values of serum albumin, beta2M, and non-involved immunoglobulins did not show statistical differences.

Conclusions: The occurrence of OB could be a potential favorable prognostic marker after transplantation due to the prolonged survival observed. Close follow-up of anomalous protein bands, either in serum or urine, is essential due to the additional difficulty in interpretation when the therapeutic response and evolution are evaluated.