In most of the 21 patients suffering lung toxicity, IL-6 and TGF-β1 plasma levels measured at the onset of RP were increased compared to their individual pre-RT values (in 17 out of 21 patients for IL-6 [81.0%]; in 15 out of 21 patients for TGF-β1 [71.4%]) (data not shown). Here, IL6 is linked to toxicity.