Big data analysis of associations between patient reported outcomes, observer reported toxicities, and overall quality of life in head and neck cancer patients treated with radiation therapy

•Recreation/entertainment, activity and fatigue are PROs most strongly associated with overall QOL.•Relatively few PRO items appear needed to capture sufficient outcome information in clinic visits.•Observer and patient reported outcomes including QOL are moderately associated.•Novel ROC-based method shows clinician assessment of patient toxicities improves with more severe toxicities.