# Medicare & Cancer: The Real Cost of Coverage Gaps

By Matthew Wood (@matthewwood) · Published 2026-08-17 · Updated 2026-08-17

Canonical: https://voce.com/@matthewwood/medicare-cancer-real-cost-coverage-gaps-cs05k7

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Most people I sit down with in my Medicare work assume their coverage will step in when a cancer diagnosis arrives. The reality is harder: Original Medicare pays a large share of treatment, but it leaves you in the path of an **uncapped 20% coinsurance**, and it never touches the non-medical costs that pile up around a diagnosis. With no annual limit on what you owe out of pocket, a serious cancer year can drain a retirement that looked secure. The good news is that knowing where the gaps sit — and closing them before treatment starts — is the difference between fighting the disease and fighting the bills.

I've spent my career as a Medicare and health insurance advisor in Clayton, North Carolina, helping families plan for exactly this scenario. This guide walks through what Original Medicare actually covers, where the dollar-shaped holes are, and what a realistic plan looks like before — not after — you need it.

#### Key Takeaways

-   Original Medicare has NO out-of-pocket maximum — the 20% Part B coinsurance on chemotherapy and radiation is uncapped, so a $10,000-a-month treatment costs you $2,000 every month.
-   Oral chemotherapy (pills taken at home) falls under Part D, not Part B — a coverage split that can shift thousands of dollars onto you depending on your plan.
-   Medicare never covers the external costs of cancer: travel to specialists, lodging, home modifications, caregiver lost income, and many prescription drugs.
-   Medigap closes the 20% coinsurance gap; Medicare Advantage caps your yearly costs but relies on networks and adds drug coverage.
-   The window to buy a Medigap policy with no medical underwriting closes 6 months after you enroll in Part B — after that, coverage may be denied or priced on your health.

## What does Original Medicare actually cover for cancer care?

The short answer: most of the medical treatment, but not all of it, and the uncovered slice has no ceiling. Original Medicare is divided into parts, and a cancer patient will likely touch all of them. **Part A** covers inpatient hospital stays — surgery to remove a tumor, a monitored chemotherapy admission, and skilled nursing after a procedure. **Part B** is the workhorse: outpatient chemotherapy and radiation, oncologist visits, CT and MRI scans, and durable equipment like wheelchairs or feeding pumps. **Part D** covers the pills you take at home, including many oral cancer drugs. Each part carries its own costs, and those costs are what create the financial danger ([Wellcare](https://www.wellcare.com/en/resources/does-medicare-cover-cancer-treatment)).

The trap hides in how the parts pay. Part B covers 80% of the Medicare-approved amount for outpatient services — but there is **no cap on the remaining 20%**. Under Original Medicare there's no out-of-pocket maximum at all, unlike the private insurance most people carried during their working years. A complex diagnosis that runs up $200,000 in a year leaves you responsible for $40,000 of it, with no wall at the end ([Wellcare](https://www.wellcare.com/en/resources/does-medicare-cover-cancer-treatment)). That single fact — no annual limit — is the root of nearly every cancer-planning conversation I have.