ScopeThe scope of this systematic review (SR) was to determine whether a nasogastric tube (NGT) or percutaneous endoscopic gastrostomy (PEG) is a more useful supportive therapy in patients with oral cancer undergoing chemoradio-/radio therapy. MethodsFor the review, two authors searched MEDLINE, Cochrane CENTRAL and Ichushi-Web to identify clinical practice guidelines, SRs and randomised controlled trials (RCTs) according to pre-determined criteria. RevMan Web was used to combine trials and analyse the data. We evaluated the certainty of the evidence using the Grading of Recommendations, Assessment, Development and Evaluation system approach. ResultsIt was not possible to perform a meta-analysis of only treatment completion based on the included RCTs; therefore, we performed a meta-analysis of treatment breaks as a surrogate outcome. A meta-analysis of potential treatment breaks, including treatment discontinuation, revealed no superiority between PEG and NGT (risk ratio=0.64 [0.23, 1.79]). A meta-analysis was conducted on two RCTs regarding the harms of infection. There does not appear to be a significant increase in the risk of infection with either PEG or NGT (risk ratio=1.18 [0.45, 3.08]). The certainty of the evidence for two outcomes was judged to be very low. Further, meta-analyses of quality of life and nutritional status were not possible because of differences in assessment methods. ConclusionWe could not determine the superiority of NGT or PEG in the supportive care of oral cancer patients who received chemoradio-/radio therapy. The effect of PEG feeding is uncertain, and it is necessary to consider indications for each case.