The prognostic significance of serum lactate dehydrogenase for patients with small cell lung cancer treated first-line therapy: a retrospective analysis of 163 consecutive cases

Abstract Purpose: To investigate the association between lactate dehydrogenase (LDH) and the prognosis of first-line therapy in patients with small cell lung cancer (SCLC). Methods: 163 small cell lung cancer patients were consecutively included from January 2011 to June 2020 as initial therapy in Fujian Medical University Union Hospital. A retrospective analysis of the clinical data were conducted to explore the association between LDH, the progression free survival (PFS) and overall survival (OS). PFS and OS were calculated using the Kaplan-Meier method and compared with the log-rank test. Results: 163 patients were divided into 90 patients in the high LDH group (pre-treatment LDH≥202 IU/L) and 73 patients in the low LDH group (pre-treatment LDH <202 IU/L). The low LDH group has a longer PFS than the high LDH group (6.23±0.28 months vs. 5.24±0.21 months; P=0.002). In the subgroup analysis of extensive stage (ES), the low LDH group has a longer PFS than the high LDH group (6.67±0.35 months vs. 5.02±0.23months; P=0.000). In the high LDH group, patients have a significantly longer PFS when treated with the cisplatin-etoposide (EP) regimen compared to those treated with the carboplatin-etoposide (EC) regimen(5.72±0.29 months vs. 4.72±0.28 months; P=0.029). Among the high-LDH group, the PFS of EP regimen in the LS subgroup was longer than that of EC regimen, with a statistical difference (6.39±0.58 months vs. 4.71±0.45 months; P=0.018). After 2 cycles of first-line treatment, the OS in the group with LDH-significant-decrease group was longer (10.44±0.77 months vs. 14.79±1.67 months; P=0.009), compared with LDH-non-significant-decrease group. In the subgroup analysis of ES patients, OS in the LDH-significant-decrease group was longer than that in the LDH-no-significant-decrease group(13.96±2.25 months vs. 9.49±0.81 months; P=0.027). In the subgroups using EP regimen, OS in the LDH-significant-decrease group was longer than that in the LDH-no-significant-decrease group (16.67±2.33 months vs. 10.20±1.03 months; P=0.004). Conclusion: LDH is of certain significance to the efficacy of first-line chemotherapy of small cell lung cancer. Higher LDH is a biomarker of poor clinical prognosis. The decrease of LDH after 2 cycles of first-line treatment may suggest longer PFS and OS for patients with SCLC. Patients with high pretreatment-LDH choosing EP treatment may have a longer PFS.