Association of fat-free mass index and survival in patients with lung cancer: a multicenter cohort study.

[BACKGROUND] Fat-free mass index (FFMI) is a prognostic influence in cancer patients. However, for the prognosis of Chinese lung cancer (LC) patients, the threshold and impact of FFMI are not known. The aim of the present study was to examine the association between FFMI and the prognosis of Chinese patients with LC.

[METHODS] Totally 1,881 adult patients with LC were enrolled. During a median follow-up of 41.0 months (range 23.8-64.3), we reported 938 deaths. The optimal stratification method was used to determine the gender-specific optimal threshold for FFMI. Cox regression model and Kaplan-Meier curve were used to evaluate the relationship between FFMI and prognosis. Mediation analysis was used to determine the mediating effect of inflammation.

[RESULTS] The optimal cutoff points for low FFMI in males and females were 17.27 kg/m and 14.84 kg/m, respectively. Low FFMI was an independent prognostic indicator for LC patients. Patients who experienced a low FFMI were 29% more likely to die than patients who did not have a low FFMI (P < 0.001, HR = 1.29, 95%CI: 1.12-1.49). The impact of low FFMI on prognosis in LC patients exhibited significant staging dependence, particularly in advanced non-small cell LC and extensive-stage small cell LC. NLR mediated 9.2% of the associations between FFMI and LC all-cause mortality.

[CONCLUSION] In this prospective study, low FFMI, as determined by cutoff values, was an independent prognostic factor for patients with LC in both males and females. The association between FFMI and LC prognosis was significantly mediated by NLR.