Radiotherapy-induced xerostomia (RIX) is one of the most common adverse effects of radiotherapy to the head and neck, and a major determinant of survivors' quality of life. A number of patient-reported outcome measures (PROMs) have been used in clinical trials of therapeutic interventions for RIX; however, little is known regarding their measurement properties and methodological quality.
We conducted a systematic literature search in Embase, MEDLINE and PsycINFO for articles published up to May 2019 and evaluating at least one measurement property of PROMs relevant to RIX. The COSMIN guidelines were used to assess relevant measurement properties and methodological quality.
Nine validations studies were identified reporting on four PROMs relevant to RIX. The Xerostomia Questionnaire (XQ) showed overall high-quality evidence for structural validity and internal consistency, but low-quality evidence supporting reliability. The methodological quality of the Groningen Radiotherapy-Induced Xerostomia scale (GRIX), Xerostomia Inventory (XI) and the Xerostomia Quality of Life Scale (XeQoLS) was relatively low for all measurement properties.
The XQ was found to have the highest potential to capture changes in RIX according to COSMIN guidelines. Additional validation studies are required to further understand the methodological quality of the XI, GRIX and XeQoLS.