“…In two 15,20 of 10 articles, the study design was retrospective. In two studies (357 patients), 7,8 only patients with lung cancer were enrolled, in another two studies (102 patients), 10,19 only patients with colorectal cancer were enrolled, in four studies (511 patients), 9,12,13,18 only patients with head and neck cancer were enrolled, and in two studies (135 patients), 1,11 mixed patient populations were enrolled.…”