Standard-of-care treatment of glioblastoma: Out-of-pocket cost modeling of adjuvant radiation therapy duration across current-year Medicaid and Medicare plans.

18 Background: The optimal radiotherapy (RT) duration for older adults with glioblastoma—6 weeks of 60 Gy in 30 fractions versus 3 weeks of 40 Gy in 15 fractions—remains a subject of debate. Level 1 evidence (PMID: 15051755) demonstrates no significant difference in survival between these regimens. However, limited data exist on how insurance coverage influences patient out-of-pocket (OOP) costs across treatment lengths. This study aims to quantify OOP expenses by insurance plan to improve cost transparency and inform patient-centered decision-making. Methods: We used NCCN guidelines to define standard treatment protocols, including 30- or 15-fraction RT with concurrent and adjuvant temozolomide for 12 cycles. The model reflects a Medicare- and/or Medicaid-eligible patient aged ≥65 with glioblastoma. Aggregate out-of-pocket costs were calculated over a two-year horizon (not adjusted for inflation) by summing treatment costs, deductibles, and copays/coinsurance under Medicaid, Original Medicare, Medigap Plan G, and Medicare Part D. All care was modeled within an Ohio hospital setting. Results: Treatment charges included neurosurgery, neurooncology and radiation oncology initial consultations, follow-up visits, diagnostic imaging (CT, MRI), craniotomy with maximum safe resection, surveillance MRI, temozolomide, antiemetics, prophylactic TMP-SMX, weekly CBCs, and tumor treating fields. RT-specific treatment charges included planning, simulation, verification, delivery, and on-treatment visits. Under Original Medicare, beneficiaries pay 20% of Medicare Part B charges with no OOP cap after the deductible. Medications are covered under Part D with applicable copays. Based on this, the OOP cost burden for 30-fraction RT exceeds that of 15-fraction RT. Medigap Plan G beneficiaries incur OOP costs of $2332.04 and $2319.42 for 30-fraction and 15-fraction RT, respectively. Medicaid fully covers all approved services, resulting in no OOP cost for either regimen. Conclusions: Three-week RT for GBM reduces patient out-of-pocket costs by nearly 10% compared to the six-week regimen. Understanding these cost differences can support more informed decision-making among clinicians, patients, and policymakers, while informing efforts to reduce the economic burden of GBM care.