Association Between Fat Mass Index, Fat Free Mass Index and Metabolic Syndrome, Cachexia, and All-Cause Mortality Among Patients with Cancer.

[BACKGROUND AND OBJECTIVE] This study examined the associations of fat mass index (FMI) and fat free mass index (FFMI) with metabolic syndrome (MetS), cachexia, and all-cause mortality in cancer patients, given the limited existing evidence on these relationships.

[MATERIALS AND METHODS] This analysis included 3,247 subjects enrolled in a cohort study. Cox regression analyses calculated hazard ratios (HRs) with corresponding 95% confidence intervals (95% CIs). Logistic models generated odds ratios (ORs) and 95% CIs. Mediation effects of FMI and FFMI on the cachexia-mortality association were evaluated.

[RESULTS] FMI and FFMI were significantly associated with MetS and cachexia, respectively. FMI (HR [95% CI] = 0.96 (0.94, 0.99),  = 0.003), FFMI (HR [95% CI] = 0.94 (0.91, 0.97),  < 0.001) were significantly associated with mortality. FMI (proportion mediated%=10.21,  = 0.03) and FFMI (proportion mediated%=13.16,  = 0.016) mediate the correlation between cachexia and mortality. Subgroup analysis showed that FMI had a significant mediating effect in gastrointestinal cancer, while FFMI had a significant mediating effect in lung cancer.

[CONCLUSION] FMI and FFMI were positively correlated with MetS, negatively correlated with cachexia and mortality. FMI and FFMI mediate the association between cachexia and mortality, with FFMI having a higher mediating effect than FMI, however, the mediating effect was differentiated by tumor types.