Patients with absent tumor hypoxia response within the first 2 weeks of treatment (Δ[18F]FMISO T/M-ratioweek 0-2 ≥0) exhibited elevated mean IL-6 plasma levels that were more than twice as high as in patients with Δ[18F]FMISO T/M-ratioweek 0-2 <0 (33.9 versus 15.8 pg/mL, p=0.016). This evidence concerns the gene IL6 and neoplasm.