Serum free light chain ratio, total kappa/lambda ratio, and immunofixation results are not prognostic factors after stem cell transplantation for newly diagnosed multiple myeloma.

Background: The prognostic value of changes in paraprotein markers after stem cell transplantation is unknown. We evaluated disease response using serum immunofixation (s-IFIX), total kappa and lambda ratio (KLR), and free light chain (FLC) ratio in myeloma patients who underwent autologous or autologous plus allogeneic stem cell transplantation.

Methods: We studied s-IFIX, KLR, and FLC ratio in sera from 203 patients, 3 months after transplantation. We evaluated overall and event-free survival (OS and EFS, interval between date of study enrollment and date of death from any cause or date of progression, relapse, or death from any cause, respectively) by the Kaplan-Meier method.

Results: Of the 203 patients, 51 were negative by s-IFIX, 99 reached a normal KLR, and 92 had a normal FLC ratio. Of the 51 patients with negative s-IFIX, 40 (78%) also had a normal FLC ratio. The median duration of OS was 54.3 months, and the median EFS was 19.5 months. None of the measured paraprotein parameters showed an association with OS. Only a normal KLR was associated with prolonged EFS (P = 0.016). Even a negative s-IFIX associated with a normal FLC ratio did not show a significant difference in terms of EFS and OS.

Conclusions: Our analysis with a small cohort of patients did not show a significant impact of achieving complete response (CR) or stringent CR on patient survival.