Background
Financial toxicity (FT) is increasingly recognised as a major patient-centred consequence across the cancer care continuum, reflecting both objective financial burden and subjective financial distress experienced by patients and their households. Head and neck cancer (HNC) patients represent a uniquely vulnerable population in this regard, given the intensity of multimodal treatment, prolonged rehabilitation, and profound long-term functional sequelae, with substantial direct and indirect costs. The lack of a standardised definition, a coherent measurement framework, or severity thresholds constrains cross-study and cross-country comparability, weakening the utility of FT evidence for equity monitoring and financial protection policies in cancer control.
 
Objective
To map conceptual and methodological inconsistencies in the definition and quantification of financial toxicity in head and neck cancer populations, and to propose a pragmatic and actionable research agenda to develop policy-relevant, comparable FT metrics and severity thresholds.
 
Method
We conducted a scoping review of peer-reviewed and grey literature published since 2010, addressing financial toxicity, financial hardship, and economic stress in adult HNC populations. Searches were performed systematically in PubMed/MEDLINE, Scopus, Web of Science, Embase, EconLit, and Global Index Medicus. We extracted reported FT definitions, measurement approaches, cut-offs and thresholds used for severity categorisation, and key findings relevant to comparability.
 
Result
Across the included studies, FT definitions vary substantially, ranging from direct medical costs and expenditure-based indicators to broader constructs centred on financial distress and coping behaviours. Measurement approaches were heterogeneous, combining cost metrics, patient-reported instruments (e.g., COST), and qualitative methodologies. Validated instruments were predominantly developed in high-income settings, and evidence from low- and middle-income countries was limited, and important gaps remain in relation to longitudinal trajectories, productivity loss, and survivorship-phase impacts. Severity categorisation relied on inconsistent, arbitrary, or poorly justified thresholds, contributing to wide variation in reported FT prevalence and limiting meaningful synthesis across settings.
 
Conclusion
In head and neck cancer, FT measurement remains insufficiently standardised to support robust comparisons, equity surveillance, or financial protection policies in cancer control. We propose a phased research agenda to establish a shared taxonomy distinguishing objective burden, subjective distress, and coping behaviours, and to define a minimum reporting set that strengthens measurement transparency and cross-setting comparability, thereby supporting policy interventions that address socioeconomic vulnerability across the HNC care continuum. Our findings also highlight the need for responsive, empirically anchored FT frameworks that can inform and strengthen financial protection across head and neck cancer care pathways in diverse health systems. Reliable, comparable, and policy-relevant FT metrics are urgently needed to inform equitable cancer-control policies and financial protection strategies.