Immunoglobulin oligoclonal bands and isotype switching after bone marrow transplantation in patients with multiple myeloma

Abstract

BACKGROUND: Appearance of new monoclonal or oligoclonal immunoglobulin bands was reported to be common in myeloma patients after receiving bone marrow transplantation (BMT). AIMS: We aimed to study this phenomenon in a cohort of Chinese patients who had received autologous or allogeneic BMT as part of the treatment of myeloma. METHODS: The clinical records and laboratory results of 41 patients over a 6-year period (2005-2010) were reviewed retrospectively. RESULTS: The distribution of the original monoclonal immunoglobulin isotypes was IgA/L (n=7), IgA/K (n=3), IgG/L (n=3), IgG/K (n=13), IgD/L (n=4), Free L (n=5), Free K (n=5), hyposecretory (n=1). After receiving BMT, 23 patients (56%) develop new monoclonal or oligoclonal immunoglobulin bands detected by serum/urine protein electrophoresis and immunofixation. Of the remaining 18 patients, 4 were followed up for only 4 months or less and new immunoglobulin bands might develop subsequently. The isotypes of the new bands found were IgG/L (n=4), IgG/K (n=12), IgM/L (n=1), Free L (n=2), oligoclonal with no light chain restriction (n=4). Of those who were followed up for at least 23 months (n=20), 8 survived and 3 succumbed if new immunoglobulin bands were found. Although not statistically significant (p>0.05 by the Fisher Exact Probability Test) this survival rate was better than those who did not have new immunoglobulin bands (3 survived, 6 died). Of those who were followed up for less than 23 months (n=21), the survival rates were similar whether new immunoglobulin bands developed or not developed (10 survived 2 died and 9 survived 0 died respectively). CONCLUSIONS: This study demonstrates new monoclonal or oligoclonal immunoglobulin bands frequently develop after patients with myeloma receive BMT. Although not significant statistically the long term survival of patients who have new immunoglobulin bands appears more favourable than those who do not have new immunoglobulin bands. A larger cohort is needed to confirm these findings.