SMD: Standardised Mean Difference; 95% CI: 95% Confidence Interval; I2: I-squared; MD: Mean Difference; WMD: Weighted Mean Difference; TNF-α: Tumour Necrosis Factor-alpha; IL-6: Interleukin-6; CRF: Cancer-Related Fatigue; 6MWT: Six-Minute Walk Test; QOL: Quality of Life. This evidence concerns the gene IL6 and cancer.