Development of a visualization tool to estimate out-of-pocket costs for systemic cancer therapy in Japan and...

Financial toxicity is increasingly recognized as a major barrier to high-quality cancer care. However, regimen-specific estimates of out-of-pocket (OOP) costs are rarely available at treatment planning. We developed VEST-Ca (Visualization of Estimated Self-pay Treatment Costs for Cancer), a rule-based visualization tool to estimate OOP expenditures for systemic anticancer therapy under Japan's universal health coverage system, and evaluated its agreement with claims-derived expenditures.

We conducted a single-center retrospective agreement study including adults with solid tumors who received outpatient systemic therapy for at least 4 months. Actual 4-month OOP expenditures were extracted from claims data. VEST-Ca simulated OOP costs using drug prices, dosing schedules, and patient-specific reimbursement ceilings under the high-cost medical expense benefit system. Accuracy was defined as (simulated OOP/actual OOP) × 100 (%). Agreement was assessed using Bland-Altman analysis. A prespecified sensitivity analysis excluded computed tomography (CT) and medical certificate-related charges.

Among 41 enrolled patients, 21 were included after excluding those with indeterminate ceiling categories. Median actual 4-month OOP expenditure was JPY 160 930, compared with a median simulated cost of JPY 121 068. Median accuracy was 93.1% and improved to 100% after excluding CT and certificate-related charges. Bland-Altman analysis showed a small negative bias (-11 705 JPY), which decreased in sensitivity analysis.

VEST-Ca demonstrated high claims-based agreement across diverse systemic regimens. A simple rule-based cost estimation tool may facilitate financial counseling and support shared decision-making in oncology.