Yes, Medicare covers immunotherapy for cancer treatment, primarily under Part B for infusions given in a doctor’s office or outpatient clinic, and under Part D for oral immunotherapy drugs taken at home. Your out-of-pocket costs depend on which parts of Medicare you have, whether you’re on Original Medicare or a Medicare Advantage plan, and whether you carry supplemental insurance.
How Part B Covers Infusion Immunotherapy
Most immunotherapy for cancer is delivered through an IV infusion at a clinic or hospital outpatient setting. These treatments fall under Medicare Part B, which covers outpatient medical services. Once Medicare approves the treatment, you pay the standard Part B cost-sharing: an annual deductible plus 20% coinsurance on the Medicare-approved amount.
That 20% matters a lot with immunotherapy. A single infusion can cost thousands of dollars, so 20% of even one treatment cycle adds up quickly. For example, if a round of immunotherapy costs $30,000, your coinsurance share would be $6,000 for that round alone, on top of your annual deductible. This is where supplemental coverage becomes important, which we’ll get to below.
Oral Immunotherapy Under Part D
If your immunotherapy comes in pill or capsule form and you take it at home, it falls under Part D, Medicare’s prescription drug benefit. Part D plans charge varying copays or coinsurance depending on which tier the drug sits on, and immunotherapy drugs are almost always placed on the highest (specialty) tier with 25% coinsurance during the initial coverage phase.
A major change took effect in 2025: Part D now caps total out-of-pocket spending at $2,000 per year. Once you hit that threshold, you pay nothing for the rest of the calendar year. Before this cap existed, patients on expensive oral cancer drugs could face tens of thousands in annual costs. For anyone taking oral immunotherapy, this $2,000 ceiling is a significant financial protection.
What Medicare Requires for Approval
Medicare generally covers immunotherapy when it’s FDA-approved for your specific cancer type and your oncologist determines it’s medically necessary. For on-label uses (meaning the drug is approved specifically for your diagnosis), coverage is straightforward under Original Medicare.
Off-label use is a different story. When an immunotherapy drug is used for a cancer type it wasn’t specifically approved for, coverage decisions fall to your regional Medicare Administrative Contractor. These are the local entities that process Medicare claims in your area. Your oncologist may need to submit additional documentation showing why the off-label use is appropriate for your situation. Some off-label uses are well-supported by medical evidence and get approved routinely; others face more scrutiny.
Coverage During Clinical Trials
If you’re considering an immunotherapy clinical trial, Medicare covers the routine costs of participating in a qualifying trial. This includes your standard medical care, administration of the treatment, monitoring for side effects, and treatment of any complications that arise from the experimental therapy.
What Medicare does not cover is the investigational drug itself. The trial sponsor (usually a pharmaceutical company or research institution) typically provides the experimental immunotherapy at no charge. Medicare also won’t pay for extra tests or scans done purely for research data collection rather than your direct medical care. In practice, this means your out-of-pocket costs during a clinical trial are often similar to what you’d pay for standard treatment, since the experimental drug is free and Medicare handles the rest.
Medicare Advantage Plans Add Extra Steps
If you’re enrolled in a Medicare Advantage plan (Part C) instead of Original Medicare, your immunotherapy is still covered, but the process looks different. Medicare Advantage plans can require prior authorization before approving expensive treatments, and immunotherapy is one of the categories where prior authorization has become increasingly common.
A study of Medicare Advantage plans found that the percentage requiring prior authorization for major immunotherapy drugs jumped from 8% in 2020 to 65% in 2022. This means your plan may need to approve the specific drug before treatment begins, which can add days or weeks to the timeline. Insurers also tend to wait about two years after a new immunotherapy drug hits the market before adding prior authorization requirements for it.
Cost-sharing in Medicare Advantage varies by plan. Some charge flat copays per infusion, others use percentage-based coinsurance, and most have an annual out-of-pocket maximum (which Original Medicare does not have). That built-in spending cap can actually work in your favor with expensive immunotherapy, since your costs stop once you reach the plan’s limit.
How Medigap Reduces Your Costs
For people on Original Medicare, a Medigap (Medicare Supplement) policy can cover most or all of that 20% Part B coinsurance. Since immunotherapy infusions are billed under Part B, this is where Medigap pays off the most. Plans A, B, D, G, M, and N all cover 100% of Part B coinsurance. Plan K covers 50% and Plan L covers 75%.
Plans C and F also cover 100%, but they’re no longer available to anyone who became Medicare-eligible after January 1, 2020. If you already had one of these plans before that date, you can keep it.
The practical impact is significant. Without Medigap, a patient receiving $100,000 worth of immunotherapy in a year would owe $20,000 in coinsurance alone under Part B. With a Medigap plan that covers 100% of Part B coinsurance, that $20,000 drops to zero (aside from the monthly Medigap premium and the Part B deductible). For anyone facing immunotherapy treatment, having Medigap coverage in place before a diagnosis is one of the most effective ways to limit financial exposure. You cannot purchase Medigap if you’re enrolled in a Medicare Advantage plan, so this protection only applies to Original Medicare beneficiaries.
Comparing Your Coverage Options
- Original Medicare alone: Part B deductible plus 20% coinsurance on every infusion, with no annual cap on what you owe.
- Original Medicare with Medigap: Monthly Medigap premium plus the Part B deductible. Most plans eliminate the 20% coinsurance entirely.
- Medicare Advantage: Varies by plan, but includes an annual out-of-pocket maximum. Expect prior authorization requirements and potentially narrower provider networks.
- Part D (oral drugs): 25% coinsurance on specialty-tier drugs until you reach the $2,000 annual cap, then $0 for the rest of the year.
If you’re currently healthy and choosing between Original Medicare with Medigap and a Medicare Advantage plan, consider that immunotherapy costs can reach six figures annually. The combination of Original Medicare plus a comprehensive Medigap plan (like Plan G) provides the most predictable cost protection and the fewest restrictions on which oncologists and cancer centers you can use.