Abstract
BACKGROUND: Elevated pretreatment lactate dehydrogenase (LDH) has been reported to be associated with poor survival in small cell lung cancer (SCLC). The present study aimed to investigate the continuous relationship between baseline LDH level and survival in patients with extensive-disease SCLC (ED-SCLC). METHODS: Data were retrospectively collected from Shanghai Health Information Network. Patients primarily diagnosed as ED-SCLC from April 2011 to August 2014 were eligible for our study. Patients' survival status was checked in March 2016. A multivariate Cox proportional hazard model was used to detect the association between baseline serum LDH and overall survival. The corresponding continuous relationship was analyzed by using natural spline functions in the Cox model. RESULTS: A total of 132 eligible ED-SCLC patients were analyzed. Elevated LDH at baseline was associated with poor survival (HR =1.92; 95% CI, 1.29-2.86). An increment of LDH would still raise the risk of death even in abnormal range. Among patients with elevated LDH, those who had relatively higher LDH levels (>370 U/L) would have a poorer prognosis than those with moderately elevated LDH levels (245-370 U/L; median survival time, 114 vs. 274 days; P value of log rank test, 0.007). CONCLUSIONS: LDH is a significant prognostic biomarker for ED-SCLC patients. The interpretation of continuous relationship between LDH and patients' survival can provide more accurate information for clinical practice.