How different body compositions affect the prognosis of HCC undergoing immunotherapy: the paradoxical phenomenon of BMI.

Purpose: Body mass index (BMI) is associated with the prognosis of hepatocellular carcinoma (HCC) receiving immunotherapy. Body compositions are considered to account for this association, but this hypothesis has yet to be verified conclusively.

Material And Methods: Our study included 305 patients received immunotherapy at 3 centers between August 2018 and February 2022. We calculated skeletal muscle index (SMI), mean skeletal muscle density (SMD), subcutaneous adipose tissue index (SATI), visceral adipose tissue index (VATI), and visceral to subcutaneous adipose tissue area ratio (VSR) at lumbar 3 level. The influences of BMI and body compositions on overall survival (OS) were comprehensively described.

Results: Sarcopenia (Low SMI, HR = 2.203, 95% CI:1.425-3.405, P < 0.001), myosteatosis (low SMD, HR = 2.013, 95% CI:1.246-3.252, P = 0.004) and visceral adipose deposition (high VATI, HR = 0.658, 95% CI:0.453-0.957, P = 0.028) were independent predictors of OS, while BMI was not. The prognosis of underweight (BMI < 20.0 kg/m, P = 0.009) and obesity (BMI ≥ 25.0 kg/m, P = 0.003) were significantly worse than normal weight (20.0 ≤ BMI ≤ 24.9 kg/m), which might attribute to the differences in body compositions. High VATI had significantly improved OS than low VATI (P = 0.002), and the difference remained significant after propensity score matching (P = 0.017).

Conclusion: In HCC receiving immunotherapy, sarcopenia, myosteatosis, and visceral adipose deposition independently predicted OS, and visceral adipose was protective in OS. The effects of BMI on OS depended on body compositions.