When it gets serious

Cancer on Medicare: the 20% with no ceiling, and how people cap it

Short answer: the shape of your bill depends on how the treatment is delivered. Chemotherapy infused in a clinic is covered by Part B at 80%, leaving you 20% with no annual limit on Original Medicare, which is how cancer becomes financially catastrophic for people without supplemental coverage. Oral cancer drugs usually fall under Part D, where the out-of-pocket cap ($2,100 in 2026, $2,400 in 2027) now provides a hard ceiling. Understanding which bucket your treatment falls into, and what caps each one, is the practical difference between a manageable year and an unbounded one.

By the Medicare Decoder team · Updated September 30, 2026 · 4-minute read · Figures are official CMS amounts, checked against CMS

Key takeaways

Infused chemotherapy and radiation are Part B: Medicare pays 80%, you pay 20%, with no annual out-of-pocket maximum on Original Medicare.
Most oral cancer drugs are Part D, where out-of-pocket spending stops at $2,100 in 2026 and $2,400 in 2027.
Some oral drugs with infused equivalents are covered under Part B instead, which changes the math entirely.
Medigap covers the Part B 20%, and Medicare Advantage caps exposure at the plan’s out-of-pocket maximum; one of the two is what makes this affordable.
Routine costs of qualifying clinical trials are covered, and every plan must offer monthly payment smoothing for drug costs.

Jump to The coverage split Why 20% with no cap is the danger What actually caps it Practical cost help FAQ

The coverage split, which decides everything

Treatment	Which part covers it	What you pay
Chemotherapy infused in a clinic or hospital outpatient	Part B	20% coinsurance, no annual cap on Original Medicare
Radiation therapy (outpatient)	Part B	20% coinsurance
Surgery, inpatient stays	Part A	$1,736 deductible per benefit period in 2026, then daily coinsurance after day 60
Oral cancer drugs, most	Part D	Deductible, then tier cost sharing, then $0 after the cap ($2,400 in 2027)
Certain oral drugs with infused equivalents	Part B	20% coinsurance rather than Part D rules
Doctor visits, scans, labs	Part B	20% after the $283 deductible in 2026

Medicare Advantage plans cover the same services with plan copays instead, subject to the plan’s out-of-pocket maximum and prior authorization rules.

The fifth row is the one that surprises oncology patients: two drugs treating the same cancer can land in different parts of Medicare with very different cost structures. It is worth asking your oncology team’s financial navigator, a role most cancer centers have, which part covers each drug in your regimen before treatment starts.

Why 20% with no cap is the real danger

Original Medicare has no annual out-of-pocket maximum. For most care that is an abstract problem; in cancer treatment it is a concrete one, because 20% of modern infused therapy can run into tens of thousands of dollars in a year, and the 20% keeps applying with nothing to stop it. This single fact is the strongest argument in all of Medicare for carrying either a Medigap policy, which pays that coinsurance, or a Medicare Advantage plan, which caps your annual exposure at its out-of-pocket maximum. It is also why the Medigap timing window at 65 matters so much: the coverage that protects you here is easiest to obtain when you are healthy and hardest after a diagnosis.

What actually caps your costs

Medigap on Original Medicare: Plan G pays the Part B 20% in full; Plan N does the same with small copays. This converts an unbounded risk into a premium.
A Medicare Advantage plan’s out-of-pocket maximum: your worst year costs the maximum, commonly several thousand dollars, plus prescription costs. Check prior authorization requirements for oncology carefully; they apply frequently in cancer care.
The Part D out-of-pocket cap: $2,100 in 2026 and $2,400 in 2027 for covered drugs, after which covered prescriptions cost nothing for the rest of the year. How the cap works.
Monthly payment smoothing: every plan must let you spread drug costs across the year rather than paying them at the counter, which matters when a regimen starts in January.
Extra Help and Savings Programs: if income is modest, Extra Help and Medicare Savings Programs reduce or eliminate large pieces of this.

Practical cost help worth asking for

Three things cancer patients consistently underuse. First, the financial navigator at your treatment center, whose job is exactly this and who knows which manufacturer assistance programs and disease-specific foundations apply to your drugs. Second, clinical trials: Medicare covers the routine costs of care in qualifying trials, so participation does not mean losing coverage. Third, appeals: prior authorization denials and coverage disputes in oncology are appealed successfully all the time, and there are expedited paths when a delay would jeopardize your health. The appeals article covers the levels and deadlines, and free help exists for working through one.

One scheduling note that saves money: Part A deductibles are charged per benefit period and Part B deductibles reset each January, so when treatment spans a year boundary, ask your team whether elective timing changes what you owe. It sometimes does, by a lot.

Questions people also ask

Does Medicare cover chemotherapy?

Yes. Chemotherapy infused in a clinic or hospital outpatient setting is covered under Part B, which pays 80% after the annual deductible, leaving 20% coinsurance with no annual cap on Original Medicare. Inpatient chemotherapy falls under Part A.

How much does cancer treatment cost with Medicare?

It depends on the coverage split. Part B treatments carry 20% coinsurance with no annual maximum on Original Medicare, while Part D drugs are capped at $2,100 in 2026 and $2,400 in 2027. Medigap or a Medicare Advantage out-of-pocket maximum is what limits the Part B exposure.

Are oral cancer drugs covered by Medicare?

Usually under Part D, where the annual out-of-pocket cap applies. Some oral drugs that have infused equivalents are covered under Part B instead, with 20% coinsurance, so it is worth confirming which part covers each drug in your regimen.

Does Medicare cover clinical trials?

Medicare covers the routine costs of care in qualifying clinical trials, meaning participation generally does not mean losing coverage for the standard care you would otherwise receive.

What is the best Medicare coverage for someone with cancer?

Whatever caps the uncapped 20%: either a Medigap policy on Original Medicare, which pays Part B coinsurance and preserves access to any provider who accepts Medicare, or a Medicare Advantage plan with an out-of-pocket maximum, keeping prior authorization requirements and network specialists in mind.

Sources for this article

Medicare.govMedicare coverage: how Parts A, B, and D cover cancer treatment, scans, and drugs.
Medicare.govPart D costs: the out-of-pocket cap and the monthly payment plan.
CMS.gov2026 Medicare premiums and deductibles: Part A and Part B deductibles and coinsurance.

Figures checked against these sources on September 30, 2026. We update within days when CMS publishes new amounts.

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