A Thyroid-Cancer-Specific Utility Index: Development and Valuation of the Thyroid Cancer Quality of Life Index

Thyroid cancer survivors experience distinctive, persistent burdens that diminish health-related quality of life (HRQoL). Utilities from patient preference-based measures are needed for quality-adjusted life-year estimation and decision-making. Generic instruments lack thyroid-specific content, limiting applicability in this population. We sought to develop a thyroid-cancer-specific utility measure, Thyroid Cancer Quality of Life Index (TCQOLI) to support clinical research, cost-effectiveness analyses, and policy applications.

We conducted a multicenter, multiphase, mixed-method, cross-sectional study. Phase 1 defined the TCQOLI domains and items using input from multidisciplinary experts and patients with thyroid cancer. Phase 2 evaluated the instrument via cognitive interviews (n = 50) and a mailed/phone-assisted psychometric survey in adults with thyroid cancer (n = 163), followed by confirmatory factor analysis (CFA) and reliability/validity analyses. Phase 3 valued health states in a separate sample (n = 103) using interviewer-administered visual analog scales (VAS; 0-100) and standard gamble (SG). Levels of morbidity in each health domain with VAS and SG were used for assessing preferences for three clinical marker states. We derived a weighted dead-to-full-health lower VAS anchor, estimated a VAS to SG power mapping solution to apply to the model overall, and constructed additive, multiplicative, and unweighted indices. Agreement of the indices with direct VAS was summarized by Pearson r, mean absolute error (MAE), overall standard deviation (OSD) of differences, and intraclass correlation (ICC).

Ten candidate domains were finalized; because one domain, reproduction concern, had the weakest psychometrics and the lowest model weight, the primary instrument uses nine domains (a 10-domain version was also evaluated). CFA supported a general HRQoL factor plus a voice/swallow factor with acceptable composite reliability and model fit. The instrument-level ceiling effect was low (3.8%) with no floor effect. The 9-domain additive multiattribute utility theory index correlated with direct VAS (r ≈ 0.74-0.75) and showed the best agreement. MAE/OSD was 0.045/0.095 after SG mapping and a good to excellent ICC of 0.74.

TCQOLI is a psychometrically robust, thyroid-cancer-specific, preference-based measure with patient-anchored valuation, suitable for health-economic evaluations. This concise index supports comparative-effectiveness research in thyroid cancer and informs resource allocation across clinical and policy settings.