Financial burden of immune checkpoint inhibitor maintenance therapy in Japan: a real-world cost analysis from an academic medical center.

BACKGROUND: Although immune checkpoint inhibitors (ICIs) have transformed cancer care today, they have also imposed substantial financial pressure on publicly funded healthcare systems. In clinical practice, ICI maintenance therapy (MT) is often continued for prolonged periods in patients without disease progression. However, analyses of the economic structure of ICI-MT remain limited. METHODS: We retrospectively analyzed regimen-based billing data patients who received outpatient drug therapy for 16 types of cancer at Iwate Medical University Hospital during the 2022 fiscal year. MT was defined as any single regimen therapy lasting 13 or more months. RESULTS: A total of 1425 patients underwent 178 therapeutic regimens across 8179 treatment opportunities, with annual costs totaling ∼2.5 billion JPY. ICI regimens were significantly more expensive than other approaches. ICI monotherapy was the most common and accounted for 44% of total drug expenditure. ICI-MT was administered to 47 patients (3%), which accounted for 473 treatment opportunities (6%). Despite its limited use, ICI-MT represented 11% of total expenditure (272 million JPY), which accounted for the largest fraction of MT cost at 64%. CONCLUSION: ICI-MT was given to only 3% of patients, but accounted for 11% or more of total expenditure, identifying prolonged ICI-MT as a concentrated driver of drug expenditures and financial burden in cancer care. These findings highlight the need for optimized treatment duration strategies in routine oncology practice, potentially supported by biomarker approaches such as circulating tumor DNA.