Value of cytoplasm light chain detection in minimal residual disease of multiple myeloma
ZHAO Yingnan1 and ZHU Jie2
Department of Clinical Laboratory, Dalian Hospital, Liaoning Provincial Corps of Chinese People’s Armed Police Forces, Dalian 116017, China; 2. Department of Laboratory, the Second Affiliated Hospital of Dalian Medical University, Dalian 116027, China
Abstract：Objective To study the role of light chain detection in the minimal residual disease (MRD) of multiple myeloma (MM). Methods The light chains of 45 bone marrow samples from the patients who were diagnosed as having MM and showed complete remission after some treatments were tested using four color flow cytometry (CD45-APC/SSC, CD38/CD56/CD19 and CD138 were detected together). The positive rate of MRD was determined according to the Results of flow cytometry and the progression of the disease of each patient was followed up. After that, whether the positive rate of MRD affected recurrence rate and disease free survival (DFS) of MM was analyzed. Results Among the 45 cases, 37 were of secretory type (IgG 27 cases; IgA 10 cases); 5 were of light chain type (λ chain:4 cases; κ chain: 1 case) and 3 were of un-secretory type. As the frequency of immunophenotype, 37/37(100%) secretory type, 1/5(20%)light chain type and 0/3(0%)showed CD38+CD56+CD19-CD45-; 4/5(80%)light chain type and 3/3(100%)un-secretory type showed CD38+CD56-CD19-CD45-; 100% (45/45) cases showed CD138+ and light chain in cytoplasm positive. Among secretory type cases, 10/37(27%)was cκ chain and 27/37(73%)was cλ chain. Among light chain type cases, 1/5(20%)was cκ chain and 4/5(80%)was cλ chain. Among un-secretory type cases, 1/3(33%)was cκchain and 2/3(67%)was cλ chain. After treatment, the samples from the complete remission patients were tested again. The positive rate of CD38+CD56+CD138+CD19-CD45- was 7/38(18%), which was significantly lower than that of CD38+CD56-CD138+CD19-CD45- (7/7, 100%), P<0.05. And there was no significant difference in MRD between cκ chain (3/12, 25%) and cλ chain (11/33, 33%), P>0.05. After 24 months’ follow-up, the recurrence rate in negative MRD group was 13％(4/31), which was significantly lower than that in positive MRD group (71％, 10/14), P<0.05. The median of disease-free interval in negative MRD group was 15.53 (9.35-21.62) months, which was significantly longer than that in positive MRD group 9.75 (3.69-14.24) months, P<0.05. Conclusions The detection of light chain in cytoplasm may be an important marker for predicting MRD in MM and it also may guide the direction of related clinic treatment.
2014, Vol. 25 
