Associations of the Fat-age-inflammation Index with Overall Survival in Patients with Metastatic Lung Cancer

Abstract: Background Metastatic lung cancer (LC) is a threat to human health. We previously proposed a fatage-inflammation (FAIN) index which showed prognostic value in patients with certain cancers. However, whether a similar association exists in patients with metastatic LC remains unknown. Methods We performed a cohort study including 1360 patients with metastatic LC from January 2013 to April 2019. The FAIN index was defined as: (triceps skinfold thickness + albumin) / [age + 5 × (neutrophil count/lymphocyte count)] × 100%. Sex-specific cutoffs of the FAIN were determined using an optimal stratification approach. The associations of the FAIN index with the nutritionrelated factors, short-term outcomes and overall survival (OS) of patients were comprehensively assessed. Results The study enrolled 865 males and 495 females with a median age of 59.9 years. The continuous FAIN was significantly associated with the OS in both genders (both P < 0.05). The optimal stratification-defined FAIN cutoffs were 82 for women and 60 for men. A total of 623 patients (45.8%) were categorized as having a low FAIN. A low FAIN was associated with poorer nutrition-related factors and impaired short-term outcomes including the thirty-day mortality, length of hospital stay, intensive care unit stay and cost (all P < 0.05). Multivariate Cox regression analysis revealed that a lower FAIN was also associated with an increased death hazard (HR = 1.428, 95%CI = 1.209-1.686). Conclusion This study assessed the FAIN index, which might act as a feasible tool to monitor nutrition-related factors and help develop management strategies to optimize the clinical outcomes of patients with metastatic LC.