The prognostic value of pretreatment prognostic nutritional index in patients with small cell lung cancer and it's influencing factors: a meta-analysis of observational studies

Background: Numerous studies identified that pretreatment prognostic nutritional index (PNI) was significantly associated with the prognosis in various kinds of malignant tumors. However, the prognostic value of PNI in small cell lung cancer (SCLC) remains controversial. We performed the present meta-analysis to estimate the prognostic value of PNI in SCLC and to explore the relationship between PNI and clinical characteristics. Methods: We systematically and comprehensively searched PubMed, EMBASE, and Web of Science for available studies until April 17, 2020. Pooled hazard ratios (HRs) and their 95% confidence intervals (CIs) were used to evaluate the correlation between PNI and overall survival (OS) and progression-free survival (PFS) in SCLC. Odds ratios (ORs) and 95% CIs were applied to evaluate the relationship between clinical features and PNI in SCLC. Results: A total of nine studies with 4,164 SCLC patients were included in the meta-analysis. The pooled data elucidated that lower PNI status was an independent risk factor for worse OS in SCLC (HR=1.43; 95% CI: 1.24-1.64; P<0.001), while there was no significant correlation between PNI status and PFS (HR=1.44; 95% CI: 0.89-2.31; P=0.134). We also found that Eastern Cooperative Oncology Group (ECOG) performance status >= 2 (OR=2.72; 95% CI: 1.63-4.53; P<0.001) and extensive-stage (ES) disease (OR=1.93; 95% CI: 1.62-2.30; P<0.001) were risk factors for low PNI, while prophylactic cranial irradiation (PCI) (OR=0.53; 95% CI: 0.40-0.69; P<0.001) was a protective factor for low PNI. Conclusions: Our findings suggested that low PNI status was closely correlated with the decreased OS in SCLC. Surveillance on PNI, amelioration of nutritional and immune status, and timely initiation of PCI may improve the prognosis of SCLC.