Significance of Oligoclonal Bands after Stem Cell Transplantation in Multiple Myeloma Cases

Multiple myeloma (MM), one of the most frequent hematological malignancies, is characterized by clonal expansion of malignant bone marrow cells engaged in the production of a unique monoclonal immunoglobulin. Switching of the paraprotein isotype or transient presence of oligoclonal bands (OB) detectable by serum immunofixation electrophoresis (IFE) have been reported following not only allogeneic transplantation ,but also after autologous transplantation and even following intensive chemotherapy for leukemia (Gerritsen et al., 1993; Zent et al., 1998). Switching of the paraprotein isotype can occur during disease relapse in MM, but the appearance of a new single band or OB may disturb the decision about consequent patient management. These OBs are likely to be due to transient dysregulation of the regenerating B cell compartment during recovery post transplant (Zent et al., 1998; Guikema et al., 1999) which has been associated with a good prognosis. It is likely due to a more durable immune reconstitution (Kyle et al., 1981; Vesole et al., 1992; Zent et al., 1998). In this study, we retrospectively analyzed 56 transplanted multiple myeloma patients’ clinical records and results of serial serum IFE, to determine the frequency and clinical significance of oligoclonal band appearance.


Introduction
Multiple myeloma (MM), one of the most frequent hematological malignancies, is characterized by clonal expansion of malignant bone marrow cells engaged in the production of a unique monoclonal immunoglobulin.Switching of the paraprotein isotype or transient presence of oligoclonal bands (OB) detectable by serum immunofixation electrophoresis (IFE) have been reported following not only allogeneic transplantation ,but also after autologous transplantation and even following intensive chemotherapy for leukemia (Gerritsen et al., 1993;Zent et al., 1998).
Switching of the paraprotein isotype can occur during disease relapse in MM, but the appearance of a new single band or OB may disturb the decision about consequent patient management.These OBs are likely to be due to transient dysregulation of the regenerating B cell compartment during recovery post transplant (Zent et al., 1998;Guikema et al., 1999) which has been associated with a good prognosis.It is likely due to a more durable immune reconstitution (Kyle et al., 1981;Vesole et al., 1992;Zent et al., 1998).
In this study, we retrospectively analyzed 56 transplanted multiple myeloma patients' clinical records and results of serial serum IFE, to determine the frequency and clinical significance of oligoclonal band appearance.

Materials and Methods
Between January 2000 and May 2011, 56 patients (29 males and 27 females, median age 51 years, range 29-69) with multiple myeloma undergoing transplantation were enrolled.The diagnosis of multiple myeloma was established according to the criteria of the World Health Organization.3 patients were excluded because of lack of ISS stage, 2 patients were stage I, 24 were stage II and 27 were stage III.48 patients received only one autologous transplantation, 8 patients received tandem stem cell transplantation (7 patients received tandem autologous transplantation, and 1 patient received autoallo tandem transplantation).24 patients received the FISH examination after 2009.Data recorded included patient and disease characteristics, and outcome data including response to treatment, relapse and survival.Myeloma responses were defined according to the criteria published by the European Group for Bone Marrow Transplantation.(Blade et al., 1998) (patients' characteristics are detailed in Table 1) Induction therapies were focused on regimen of VAD (16 patients), regimen of BD±T (26 patients), regimen of BAD±T (13 patients), and regimen TD (1 patient).The most commonly utilized regimen of mobilization was high-dose cyclophosphamide or regimen of E-CHOP and cytokine protocols.Peripheral blood progenitor cells were mobilized with a target minimum CD34+ cell count of 2.0×10 6 /kg.Patients all received high-dose therapy consisting of melphalan 200 mg/m 2 i.v. on day-1 ± bortezomib 1.0mg/m 2 day -6, -3, +1, +4.Peripheral blood progenitor cells were infused on day 0. Routine maintenance chemotherapy post-transplant was not utilized in the early study period.After 2005, some patients were managed on a thalidomide ± interferon maintenance therapy (V: vindesine, A: epirubicin, D: dexamethasone, B: bortezomib, T:thalidomide, C: cyclophosphamide, P: Prednisone, and E: Etoposide).Serum and urine protein electrophoresis and immunofixation were performed by Hydrasys 2 System (Sebia, France), Serum and urine protein were quantified by Beckman image (America).
Statistical tests were performed with SPSS software 16.0 for Windows ® , estimating 95% confidence interval (CI) by Wilson's test.
Eight were excluded from analysis due to lack of first year follow-up data after transplantation.Other patients received SPEP and IFE every one or two months during the first year after stem cell transplantation.Twelve (25.0%, 12/48) patients developed small OBs on serum protein electrophoresis in the post-transplant period, but clonal plasmas were not seen in bone marrow flow cytometry analysis at the same time.The median time to development of an episode of OBs was 1.4 months post-transplant (range, 1-3), and they persisted for a median duration of 5.8 months (range, 1-15).Eleven patients achieved CR after OBs disappeared, and 1 patient was still PR. 2 patients of the patients with OBs relapsed, and one of them died, OS was 56months A comparison between the patients with or without OBs is shown in Table 2 .Of the 12 patients with OBs, one patients relapsed, and the PFS was 11 months.One patient had two episodes of OBs, and three patients had three episodes.The quantities of OBs were normal or slightly elevated (Table 3, Figure 1).The relationship between post-transplant response and OS could not be analyzed because of the short followup.Compared to those who had a normal SPEP, the 12 patients who developed OBs had superior progressionfree survival (1 year PFS 92% vs 66.7%, p=0.002), for comparison of PFS see Figure 2. Overall survival was not analyzed.

Discussion
We have reported a single institute's experience of oligoclonal band detection in 12 patients with multiple myeloma, after receiving autologous or allogeneic hematopoietic stem cell transplantation.The prevalence, etiology, and clinical significance of this event is still unknown.In 25.0% (12/48) of patients, OBs occurred at a median of 1.4 months post-transplant.This incidence was reported to be 73% by Sala et al. (2009) and Hovenga et al. (2000), 10% by Zent et al.(1998), and 43% by Maisnar et al. (2007).The differences in incidence of these small bands may be related to assay sensitivity (Tormey, 1989).
Previous studies have shown that antibody production is impaired after allogeneic and autologous stem cell transplantation and that transient OBs detectable in serum IFE are common during the recovery of Ig production (Mitus et al., 1989;Gerritsen et al., 1993;1994).So the presence of OBs after transplantation could be related to the recovery of impaired Ig production rather than to a change in the paraprotein production by the malignant plasma cell clone.This B cell reconstitution recapitulates normal ontogeny but in a clonally dysregulated fashion, which may last more than 5 years after transplantation, probably as a result of impaired T-cell regulation (Velardi et al., 1988;Small et al., 1990;Bergsagel et al., 1996).
In assessing OBs, isoelectric focusing (IEF) proved to be a useful tool.It can immediately demonstrate which discrete bands are oligoclonal and thus are not clinically concerned with disease relapse.Isoelectric focusing also documented the presence of discrete bands of up to 5g/L which appeared monoclonal, but had different immunoglobulin or electrophoretic properties to the original myeloma paraprotein.But we have not been able do this examination in our center till now.
The appearance of OBs should be considered as an additional serum marker for the evaluation of prognosis in allogeneic and autologous stem cell transplantation patients due to the mean OS times obtained for these patients (Mariel et al., 2010).Hari reported the same conclusions, indicating the need for newer schemes incorporating other prognosis markers.This is because neither of the systems currently used are strongly predictive of outcomes for all stages (Hari et al., 2009).
The serum free light chain (FLC) ratio appears to be an independent risk factor for progression, and a sensitive technique for monitoring disease response and relapse.However, a previous report showed that the incidence of abnormal serum FLC κ/λ ratios in patients with MM and long lasting CR indeed correlated with the presence of OBs ( De Larrea et al., 2009).But we did not have the data of serum FLc measurements in our study.
In our data, there was only one patient with OBs that really relapsed, much lower than the patients without OBs.This patient relapsed 6 months after the OBs disappeared.Some PR patients with OBs reached CR after OBs disappeared, one year PFS of the patients with OBs was superior to the patients without OBs.So OBs may not be a bad clinical event, but the appearance of OBs in the post-transplant setting may cause clinician confusion, and disturb the decision making of the treatment.Although its clinical significance is uncertain, it needs carefully monitoring by the laboratory.
In summary, the development of small OBs and immunoglobulin isotype switch post-transplant in patients with myeloma is common, appears to have no adverse clinical significance and can not be considered a sign of disease relapse.Nonetheless, the appearance of such small OBs and immunoglobulin isotype switch requires careful reporting and monitoring as these bands may occasionally represent true isotype switching leading to disease relapse.