Abstract: Objective  To study the clinical significance of serum thymidine kinase 1(TK1) in the treatment and prognosis of multiple myeloma(MM). Methods  A total of 32 patients with multiple myeloma were included as MM group, 20 patients with monoclonal gammopathy of undetermined significance were included as monoclonal gammopathy  of undetermined significance（MGUS） group, and 20 healthy subjects were included as healthy control group. The differences of lactate dehydrogenase (LDH),  β2microglobulin (β2MG), globulin(GLB) and TK1 levels in  three groups were analyzed.The MM group was divided into Ⅰ,  Ⅱ,  Ⅲ stage groups according to MM internationalstaging system(ISS).The  differences of LDH, β2MG,  GLB and TK1 levels  in three groups were analyzed. The correlation between serum TK1 levels and LDH, β2MG,  GLB levels before  treatment  were  analyzed  by Pearson.  All patients in MM group were treated with chemotherapy. The TK1 expression levels were compared amomg CR/PR/SD/PD patients.The median survival of different TK1 levels in treatment group were analyzed. The effect of serum TK1 in the treatment and prognosis of patients with MM were analyzed.Results  The levels of serum β2MG, GLB, LDH and TK1 in MM group had significant difference with those in MGUS group and healthy control group(P<0.05). The levels of serum β2MG, GLB, LDH and TK1 levels in stage Ⅱ and  Ⅲ  had significant difference with those in stage Ⅰ(P<0.05). The levels of serum β2MG, GLB, LDH and TK1 in stage Ⅲ had significant difference with those in stage Ⅱ(P<0.05) .Serum TK1  levels were positively correlated with the levels of β2MG, GLB, LDH. After treatment,  TK1 expression level of CR/PR patients decreased significantly (P<0.05). The overall survival  rate in TK1<4.97 pmol/L and  TK1≥4.97  pmol/L groups were 64.7% and 20.0%  according to the  survival curve of KaplanMeier(P<0.05). Conclusion  The  serum levels of TK1 in patients with MM were significantly higher, and the level of TK1 has a certain reference significance for the evaluation of therapeutic effect, and affects the prognosis of  MM  patients.

Key words: multiple myeloma；thymidine kinase, monoclonal gammopathy of undetermined significance