Evaluation Of Immunoglobulin Variations (Clonal Changes) In Symptomatic Multiple Myeloma (MM) Patients’ Course
Authors: Nikolaou Eftychia , Panayiotidis Panayiotis , Sarris Katerina , Maltezas Dimitrios , Koulieris Efstathios , Iliakis Theodoros , Vyniou Nora , Vardounioti Ioanna , Karali Vassiliki , Pessach Ilias , Efthymiou Anna , Bartzis Vassiliki , Tzenou Tatiana , Dimou Maria , Vassilakopoulos Theodoros P. , Angelopoulou Maria K. , Tsaftaridis Panagiotis , Kafasi Nikolitsa , Kyrtsonis Marie-Christine 
Published: October 2019

Abstract
Changes in the production of monoclonal intact immunoglobulin (M-Ig) or of serum free light chains (sFLC) during symptomatic MM patients’ relapse eventually reflect molecular myeloma cells changes and / or reveal clonal cell competition.
We aimed to study changes in Ig production (CIg) in symptomatic MM patients and to evaluate related frequency and corresponding specific disease characteristics.

Patients and Methods
232 symptomatic MM patients with available follow-up sFLC measurements, were retrospectively studied. Light chain escape (LCE) was defined as sFLC increase with stable or falling M-Ig concentrations, M-Ig escape (MCE) as decreasing sFLC with increasing M-Ig, de-differentiation (DD) as clinical relapse with normal or decreased M-Ig and sFLC and Clonal Domination (CD) as normalization of formerly increased IgG, IgA or FLC in relapsing patients presenting increase of another component. Survival was calculated from diagnosis or from CIg date to last follow-up or death, survival curves were plotted by Kaplan-Meyer Method and assessed by the log-rank test.

Results
There were 94 women and 128 men, median aged 66 years; 29%, 42%, 29% and 22%, 30%, 48% were in Durie-Salmon and ISS stages I, II, III and 1, 2, 3 respectively. MM type was IgG MM in 59%, IgA in 21%, light chain only in 17%, IgD in 2% and non-secretory in1%. Median survival of the whole cohort was 46,4 months. CIg was observed in 39 patients (17%), consisting in LCE in 15 patients (6%), MCE in 7 (3%), DD in 5 (2%) and CD in 10 (4%); two additional patients (1 IgD and 1 LC) transiently produced another monoclonal component that was IgG in both cases, while in stringent complete remission. In CD patients, the dominated clone was IgG in 9 out of 10 patients, while the dominating one was LC in 8 and IgA in 2. LCE and MCE were more frequent in IgG patients. The median number of treatment lines received prior CIg was 5 for LCE, 4 for MCE, 2 for DD and 1 for CD. LCE and MCE patients had all received novel agents and/or ASCT. The median time from CIg to last follow-up or death was 2,6 months (2,2-3) for LCE, 3,3 months (2,2-4,4) for MCE, 6,3 months (1,1-11,6) for DD and 31,1 months (23,6-38,6) for CD. Patients presenting LCE, MCE and DD had a considerably shorter survival after CIg compared to patients presenting CD (p=0,0002). However because CIg was usually a late event in the course of the disease the overall survival of CIg patients was 60,6 months.
In conclusion, LCE, MCE and DD are late events in the course of MM, mainly observed in patients whose previous treatments included with novel drugs. They reflect a very aggressive disease behavior with shortened survival thereafter, probably due to the emergence of a new resistant clone. CD was mainly observed in patients secreting low IgG levels and FLCs, and possibly reflect IgG clone remission in biclonal patients, given that thereafter, the disease behaves as a usual multiple myeloma, secreting however the other clone.

Disclosures:
No relevant conflicts of interest to declare.