CD274 and neoplasm: Key sources of heterogeneity likely include smoking history and intensity; performance status and comorbidities; cachexia, weight loss trajectory, and systemic inflammation; treatment line and regimen; tumor PD-L1 level and tumour mutational burden; definitions and cutoffs for skeletal muscle index and skeletal muscle density by sex and region; imaging approach single slice L3 versus volumetric segmentation; and analytic choices including immortal time bias, adjustment sets, and handling of missing data.