27 2 Figure 1. PRISMA flowchart of the literature search and study selection Summarized literature search methodology, in accordance to the PRISMA Statement20 As stated in the inclusion criteria, HR-QoL outcomes were assessed in all studies by using the UW-QoL questionnaire. In addition, some studies also used the Oral Health Impact Profile (OHIP-14 or OHIP-49) questionnaire,34,38,40,42,43 and one study used the European Organization for Research and Treatment of Cancer Head and Neck Cancer module (EORTC QLQ-H&N35).43 Evaluation of HR-QoL outcomes was performed at different moments in time. In some studies, patients administered the questionnaire at least once pre- and posttreatment.24,41 Patients in other studies administered the questionnaire only once posttreatment.23,25,26,28,30,32-38,40,42,44-49 The questionnaire was administered twice post-treatment in two studies.31,43 The follow-up time between treatment and assessment of HR-QoL varied from less than 3 months46 to 10 years.31 Characteristics and assessment details are presented in Table 1. Risk of bias within studies The methodological quality of all studies was assessed and is presented in Table 2. The MINORS quality scores of non-comparative studies ranged from 44%23 to 69%,34,36,46 with an average of 60%. The MINORS quality scores of comparative studies ranged from 54%45,49 to 75%,28,33,34,41,44,47 with an average of 67%.