Background. The minimal clinically important difference (MCID) is defined as the smallest difference in quality of life (QOL) that patients perceive as beneficial and that mandates a change in management. We aimed to determine the MCID among patients with oral cavity and oropharyngeal cancer and to identify domains that are significantly affected during treatment. Methods. The cohort consisted of 1,011 patients analyzed by a metaanalysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. MCID values for the University of Washington Quality of Life Questionnaire (UW-QOLQ) and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC C-30) and Head and Neck-35 questionnaires were calculated by using the distribution-based method. Results. The mean MCID for Global QOL was 13.07 points for the UW-QOLQ and 9.43 in the EORTC C-30 questionnaire. High consistency in the MCID values was found between the two questionnaires examined. Heat map analysis indicated a clinically significant improvement in head and neck-associated domains and in domains associated with general cancer treatment 1 year or more after treatment relative to 3 months after treatment (p < 0.001 and p = 0.016, respectively). In contrast, improvement in general and functional domains was not evident 1 year or more after treatment (p = 0.69). Conclusions. This study suggests benchmark values for MCID and variation in QOL scores of oral and oropharyngeal cancer patients after treatment. Improvement in head and neck- and general cancer-associated domains may not be translated into a general and functional improvement during the first year of recovery.
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