Introduction: Well-differentiated thyroid carcinoma (WDTC) is the most common type of thyroid cancer with a notable increasing incidence worldwide. It is prevalent among Filipino descent as compared to other nationalities. Its good prognosis and high survival rate predispose patients to lifetime surveillance with incomplete response, instead of death, as outcome measure. This eventually leads to increase in cost of care, utilization, and allocation of medical resources for the survivors of the disease. Thyroglobulin immunoradiometric assay (Tg IRMA) and I-131 diagnostic whole-body scan (dWBS) are two nuclear medicine procedures that are part of WDTC surveillance. Due to their varied availability in Asia-Pacific, most clinicians measure thyroglobulin (Tg) alone due to perceived cost-effectiveness. Objective: This study aims to analyze the cost-effectiveness of two nuclear medicine procedures used in WDTC surveillance, namely thyroglobulin immunoradiometric assay and I-131 diagnostic whole-body scan, in detecting incomplete response. Methodology: Three clinical guidelines on WDTC management were reviewed to identify frequency, total number and expenditure for surveillance, namely from the University of the Philippines-Philippine General Hospital in 2008 (PGH 2008), American Thyroid Association in 2015 (ATA 2015), and the Department of Health (DOH 2021). A Markov model was constructed to simulate a 36-month surveillance with complete and incomplete response to treatment as disease states. Parameter values like rate of incomplete response in WDTC patients, prognostic values per each surveillance test, and other relevant data were collected from literature search and established data. The cost of surveillance was based on the rates offered by Philippine General Hospital (PGH) Radioisotope Laboratory as of November 2022. One-way sensitivity was done to check robustness of results. Results: ATA 2015 incurs the most expenses, amounting to PHP 14,600.00 to 20,450.00 ($ 254.19 – 356.04) for three years of surveillance, followed by DOH 2021 (PHP 11,700.00 – 15,600.00 or $ 203.74 – 271.65), and PGH 2008 (PHP 3,900.00 – 6,825.00 or $ 67.91 – 118.85). The thyroglobulin IRMA arm costs lower (PHP 17,784.00 or $ 309.74) than I-131 dWBS (PHP 271,875.00 or $ 4,735.13) in detecting incomplete response. I-131 dWBS should cost around PHP 570.00 (or $ 9.92) to be as cost-effective as the thyroglobulin IRMA. Conclusion This study has identified that thyroglobulin IRMA is more cost-effective than I-131 diagnostic whole-body scan in detecting incomplete response in WDTC patients. This supports the perceived cost-effectiveness of thyroglobulin measurement in surveillance, even without diagnostic whole body-scans. This study also identified that the new DOH 2021 guidelines will incur lesser expenditure in using nuclear medicine procedures for surveillance as compared to ATA 2015 guidelines. Local clinicians may also find it easier to follow as it is more suitable to the Philippine setting.
Cost-Effectiveness Analysis