Abstract:Objective To explore the significance of serum lactate dehydrogenase (LDH), plasma D-dimer (D-D) and serum progastrin-releasing peptide (proGRP) levels in the evaluation of chemotherapy efficacy and prognosis in patients with small cell lung cancer (SCLC). Methods From January 2018 to June 2021,100 patients with inoperable SCLC hospitalized in the Affiliated Tumor Hospital of Shaanxi University of Chinese Medicine were selected, including 39 limited-stage (LS) patients and 61 extensive-stage (ES) patients. Before and after etoposide combined with platinum chemotherapy for 2-cycle, venous blood was drawn to detect the serum levels of LDH, proGRP and plasma D-D, which were observed and analyzed. The patients' progression-free survival (PFS) period was recorded during follow-up period. Results After chemotherapy, the patients were divided into effective group (n=75) and ineffective group (n=25). In effective group, the levels of LDH, D-D and proGRP after chemotherapy were significantly lower than those before chemotherapy (P＜0.05), and there was no significant difference in them in ineffective group (P＞0.05). There were statistical differences in the curative effects between patients with LDH ＜ the upper limit of normal (ULN) and patients with LDH ≥ ULN and between patients with proGRP ＜ ULN and patients with proGRPH ≥ ULN (P＜0.05). However, there was no significant differences in the curative effect between patients with different D-D levels (P＞0.05). PFS was significantly prolonged in the patients in LS and with LDH＜ULN, decreased LDH level after chemotherapy, proGRP＜ULN before chemotherapy and decreased proGRP level after chemotherapy (P＜0.05). In effective group, PFS in the patients with LDH＜ULN and proGRP＜ULN was significantly longer than that of patients with LDH ≥ ULN and proGRP ≥ ULN (P＜0.05). Multivariate Cox regression analysis showed that tumor stage and proGRP level before chemotherapy , LDH level after chemotherapy, and changes of LDH and proGRP before and after chemotherapy were the prognostic factors of SCLC patients (P＜0.05). Spearman correlation analysis showed that the change rates of serum LDH, proGRP and plasma D-D levels between pre-chemo therapy and post-chemotherapy were before and after chemotherapy was significantly correlated with the efficacy of chemotherapy (P＜0.05), the change rates of serum LDH and proGRP levels were correlated with prognosis (P＜0.05), and the change rate of D-D was not related to prognosis (P＞0.05). Conclusion The combined detection of serum LDH, proGRP and plasma D-D can evaluate the efficacy of chemotherapy, monitor the dynamic changes of patients' condition and predict the prognosis of patients with SCLC.