Predictive value of serum low density lipoprotein for first-line treatment in extensive-stage small cell lung cancer

Objective To investigate the relationship between serum low density lipoprotein (LDL) and the progression-free survival (PFS) of small cell lung cancer (SCLC) patients. Methods A total of 271 SCLC patients admitted to Shandong Cancer Hospital from May 1, 2014 to October 31, 2018 were selected. These patients were divided into limited-stage group (n=126) and extensive-stage group (n=145) according to Veteran′s Administration Lung Cancer Study Group (VALSG) evaluation standard. The correlation between the level of serum LDL before treatment and PFS was analyzed by Spearmen test in the two groups. After finding the cutoff value of LDL level by receiver operating characteristic curve (ROC) analysis, the relationship between LDL level before treatment and PFS was analyzed. According to the dynamic change of serum LDL during the treatment, extensive-stage patients were divided into four groups: normalized LDL group (n=25, patients whose LDL≤2.55 mmol/L and never increased until progression), increased LDL group (n=31, patients whose LDL≤2.55 mmol/L and increased at least once until progression), never-normalized LDL group (n=33, patients whose LDL>2.55 mmol/L and never normalized until progression), and decreased LDL group (n=56, patients whose LDL>2.55 mmol/L and decreased at least once until progression). Then the PFS among the four groups was compared. The survival curves were plotted by the Kaplan-Meier method and compared using the log-rank test. The significance of the independent variables for PFS in extensive-stage patients was analyzed using the Cox proportional hazards model. Results The median PFS for the whole cohorts was 7.1 months (1.4-27.1 months). The median PFS for limited-stage patients and extensive-stage ones was 8.8 months and 6.1 months respectively, with a significant statistical difference (χ2=28.723, P 2.55 mmol/L, n=164) for whole cohorts (9.0 months vs. 6.2 months, χ2=16.064, P 2.55 mmol/L before treatment (HR=0.436, 95%CI: 0.297-0.640, P 2.55 mmol/L and never normalized until progression (HR=2.215, 95%CI: 1.403-3.497, P 2.55 mmol/L before treatment (HR=0.435, 95%CI: 0.300-0.632, P 2.55 mmol/L and never normalized until progression (HR=2.028, 95% CI: 1.386-2.966, P<0.001) were independent risk factors for PFS, LDL normal during treatment (HR=0.318, 95%CI: 0.186-0.542, P<0.001) was independent protective factors of PFS. Conclusion The serum LDL level may be used as a potential predictive marker for PFS in extensive-stage SCLC patients subjected to the first-line chemotherapy. Key words: Lipoproteins, LDL; Small cell lung carcinoma; Treatment outcome; Forecasting; Progression-free survival