She enrolled in Medicare Advantage at 65. The plan offered dental coverage, a fitness membership, and no additional premium beyond Part B. Her primary care physician was in-network. The annual enrollment period advertising had been persuasive, and the broker confirmed the plan was a good fit.
Seven years later, she was diagnosed with ovarian cancer. Her oncologist — a gynecologic oncology specialist at the regional cancer center — was not in her plan’s network. The cancer center itself was not in-network. Prior authorization for her initial treatment protocol required weeks of back-and-forth between her oncologist’s office and the plan. She wanted to return to traditional Medicare, where any Medicare-participating oncologist, at any Medicare-participating cancer center in the country, would be covered without prior authorization.
She called her state insurance commissioner’s office. In her state, Medigap insurers can underwrite based on health status for beneficiaries who have been enrolled in Medicare Advantage. With a new ovarian cancer diagnosis, she was either uninsurable or insurable only at a premium she could not afford on a fixed income. Returning to traditional Medicare was legally possible. Affording the cost-sharing without Medigap was not.
The enrollment decision she made at 65, when she was healthy, had locked her into a coverage structure that was most inadequate at the moment she needed it most.
That is not an accident of the Medicare Advantage system. It is the system working as its financial logic requires.
The Evidence on Disenrollment
The pattern documented in the scenario above is not anecdotal. It is a consistent finding across the published research literature on Medicare Advantage disenrollment.
Medicare Advantage enrollees who develop serious illness — cancer, heart failure, end-stage renal disease, significant disability — disenroll back to traditional Medicare at substantially higher rates than the general MA population. The research documenting this pattern spans more than a decade and multiple study designs.
A GAO report in 2021 found that Medicare Advantage beneficiaries in the last year of life disproportionately disenrolled from MA to traditional Medicare — a pattern the GAO flagged as indicating “possible issues with their care” in the MA setting at the end of life.
A study published in JAMA (2023) examining MA disenrollment patterns among beneficiaries with multiple chronic conditions found higher disenrollment rates among the most medically complex enrollees — those with the greatest care needs and, therefore, the greatest exposure to MA’s prior authorization requirements, network restrictions, and coverage limitations.
A Health Affairs study (2025) using a 20 percent random sample of Medicare beneficiaries from 2015 to 2019 examined how Medigap guaranteed-issue regulations affected disenrollment. The finding was direct: MA disenrollment following a serious health shock was 2.75 percent in states with both guaranteed-issue and community-rating Medigap protections, compared to 1.42 percent in states with neither regulation. In other words, when the financial barrier to returning to traditional Medicare was removed — when Medigap was available regardless of health status — seriously ill MA enrollees left the program at nearly double the rate.
The implication is significant: the Medigap underwriting barrier is suppressing disenrollment among enrollees who would otherwise return to traditional Medicare following a serious diagnosis. The observed disenrollment rate understates how many seriously ill MA enrollees would prefer traditional Medicare if the switch were financially feasible.
A study published in JCO Oncology Practice (Kwon et al., 2025) examined the same dynamic specifically among cancer patients: MA beneficiaries newly diagnosed with cancer in states with Medigap guaranteed-issue protections were 2.5 percentage points more likely to switch to traditional Medicare following diagnosis — a 120 percent relative increase compared to those in states without such protections. Cancer patients who could access Medigap without health-status underwriting voted with their feet. Those who could not were left in the coverage structure they had enrolled in when healthy.
The Medigap Lock-In Mechanism
The lock-in that prevents seriously ill MA enrollees from returning to traditional Medicare is not a bug in the system. It is a structural feature that the coverage map instruction flags as one of the most consequential undisclosed consequences of MA enrollment.
Federal law guarantees Medigap coverage without health-status underwriting — guaranteed-issue rights — at specific moments. The most significant is initial Medicare eligibility: during a six-month open enrollment window beginning when a beneficiary turns 65 and enrolls in Part B, any Medigap insurer must sell any Medigap plan at standard rates, regardless of health status. This is the window during which enrolling in Medicare Advantage — rather than traditional Medicare with a Medigap supplement — forfeits most Medigap guaranteed-issue rights.
After that window closes, Medigap guaranteed-issue rights are limited to specific qualifying events: certain plan terminations, loss of other coverage, and a small number of other circumstances. Developing cancer, heart failure, or any other serious illness is not a qualifying event for Medigap guaranteed-issue rights in most states.
The result is the lock-in: a beneficiary who enrolled in MA at 65, while healthy, and who later develops serious illness, cannot purchase Medigap at standard rates in most states. She can disenroll from MA and return to traditional Medicare — that right exists. But traditional Medicare without Medigap exposes her to the program’s cost-sharing: the Part A hospital deductible ($1,676 per benefit period in 2025, with no cap on how many benefit periods she can have in a year), the 20 percent Part B coinsurance on all outpatient services with no annual out-of-pocket maximum. For a cancer patient facing extended chemotherapy, surgery, and radiation, that cost-sharing can be catastrophic.
As of the current writing, four states — Connecticut, Maine, Massachusetts, and New York — require Medigap guaranteed-issue protections beyond the federal floor for beneficiaries ages 65 and older. Connecticut and New York offer continuous guaranteed issue year-round. Massachusetts requires a two-month annual guaranteed-issue window (February through March). Maine requires guaranteed issue during a one-month annual window but limits it to Plan A, which is less comprehensive than plans like Plan G. Minnesota and Vermont require community rating — preventing insurers from varying premiums by health status — but do not require guaranteed issue, meaning access outside designated enrollment windows can still be denied. In all remaining states, beneficiaries who have enrolled in MA and later want to purchase Medigap are subject to health-status underwriting and can be denied or charged higher premiums based on their medical history (KFF, 2025).
What Happens to Care Quality at Diagnosis
The disenrollment pattern — seriously ill MA enrollees leaving the program — implies that those who stay do so because they cannot afford to leave, not because the coverage is meeting their needs. The research on what happens to care quality for seriously ill beneficiaries who remain in MA is consistent with that interpretation.
A 2023 study published in the Journal of Clinical Oncology (Raoof et al.) examined outcomes for Medicare Advantage enrollees requiring complex cancer surgery — among the highest-acuity, highest-cost care in the Medicare population. The finding: MA enrollees were less likely to be treated at specialized cancer centers, experienced longer delays from diagnosis to surgery, and had higher mortality rates than traditional Medicare beneficiaries requiring the same procedures.
This finding is the clinical consequence of the network and prior authorization dynamics documented in Articles 07 and 09. MA plans that exclude high-volume cancer centers from their networks — which the research documents as a common pattern — direct their enrollees toward in-network facilities that may not offer the same subspecialty expertise. Prior authorization requirements for cancer treatment protocols impose delays that, for conditions where treatment timing matters, translate directly into outcomes.
A study published in JAMA Health Forum (March 2024) found that MA plans provide less home health services than traditional Medicare, and that MA enrollees have worse functional outcomes compared to traditional Medicare beneficiaries receiving home health. Home health services are the post-acute care that frequently follows cancer surgery, cardiac events, and other serious illness — the category where Article 07 documented OIG finding the most concentrated pattern of prior authorization denial.
The beneficiary navigating serious illness in a Medicare Advantage plan faces a compounding set of coverage limitations — network restrictions that may exclude her preferred specialists, prior authorization requirements that may delay or deny recommended treatments, and a Medigap lock-in that makes switching to traditional Medicare financially prohibitive. Those limitations do not individually constitute a coverage failure. Together, at the point of greatest clinical need, they constitute the documented pattern of worse outcomes that the research literature records.
The Hospice Carve-Out
End-of-life care in Medicare Advantage involves a structural anomaly that creates specific coverage problems: the hospice carve-out.
Traditional Medicare covers hospice care under Medicare Part A. Hospice is a comprehensive benefit: it covers the full range of end-of-life services — physician and nursing care, medication for symptom management, social work, chaplaincy, and bereavement support — for beneficiaries with a terminal prognosis and a documented election of comfort-focused care. The benefit is designed to provide comprehensive palliative support without requiring beneficiaries or families to navigate a separate coverage structure.
Medicare Advantage plans are required to cover hospice, but the hospice benefit operates as a carve-out from the MA payment structure. When an MA enrollee elects hospice, the hospice benefit reverts to traditional Medicare Part A for payment purposes. The MA plan is required to cover any services related to conditions other than the terminal diagnosis during the hospice period, while traditional Medicare covers the hospice benefit itself.
This bifurcated structure creates coordination problems at a moment when simplicity matters most. An MA enrollee who elects hospice may face coverage questions about which conditions are related to the terminal diagnosis — managed by traditional Medicare through the hospice provider — and which are unrelated and covered by the MA plan. The plan and the hospice provider may disagree about that distinction. Resolution requires administrative interaction between the MA plan, the hospice agency, and sometimes CMS — interactions that occur while the enrollee and family are managing the final stage of serious illness.
OIG and CMS have documented compliance problems with MA hospice coverage. Cases of MA plans failing to cover services they were required to cover for hospice enrollees, and of hospice providers struggling to obtain payment for services that fell into the coordination gap, are documented in CMS audit findings.
The Cost Transfer to Traditional Medicare
The disenrollment pattern has a fiscal consequence beyond the individual beneficiary. When seriously ill MA enrollees return to traditional Medicare — whether at diagnosis, during treatment, or at the end of life — traditional Medicare absorbs the cost of their care. The government’s payment to the MA insurer stops when the beneficiary disenrolls. Traditional Medicare begins paying for the highest-cost phase of that beneficiary’s healthcare.
This means the Medicare Advantage program has collected years of capitated payments for an enrollee during the period when she was healthy and low-cost, and has transferred her to traditional Medicare at the point when she becomes high-cost. The capitated payment was calibrated — nominally — for average Medicare costs. It was not calibrated for what the beneficiary’s care actually cost in her final years, because those years were spent in traditional Medicare.
MedPAC and academic researchers have identified this cost-transfer pattern as a structural issue in Medicare Advantage’s relationship to the broader Medicare program. The insurer captures the premium during the low-cost enrollment period. The public program absorbs the high-cost care at the end. The actuarial logic of the Medicare program as a whole is affected by this dynamic — traditional Medicare’s risk pool is progressively skewed toward higher-cost enrollees as healthier ones remain in MA and seriously ill ones disenroll back.
The aggregate effect of this pattern on traditional Medicare’s long-term financing has not been fully quantified in the published literature. The directional effect is documented: the MA program systematically transfers high-cost care back to the public program at the point of greatest cost while retaining the premium collection during the preceding low-cost period.
What This Article Documents
The disenrollment evidence, the Medigap lock-in mechanism, the care quality findings at diagnosis, the hospice carve-out, and the cost transfer together document a coherent pattern: Medicare Advantage is structurally optimized for the healthy enrollment period and structurally misaligned with the seriously ill beneficiary’s needs.
The marketing machinery documented in Article 03 is designed to attract healthy 65-year-olds. The financial structure documented in Articles 04 through 06 is designed to maximize the margin between the capitated payment and the cost of care — which means minimizing care delivered. The prior authorization and network restriction patterns documented in Articles 07 through 09 are the operational mechanisms through which that minimization is applied. And the disenrollment pattern documented here is the downstream outcome: beneficiaries who most need comprehensive coverage are the least able to access it within MA, and the least able to afford what it would cost to leave.
This is not an indictment of the people who work at Medicare Advantage plans. It is a description of what the financial architecture of the program produces when its incentives are followed. The incentives are followed because they are incentives — because the insurer is a profit-maximizing entity operating a capitated public program whose margin increases when less care is delivered. The program’s design produces the documented outcome.
What to do about it is the subject of the final two articles.
The complete Medicare Advantage series
01 — What Medicare Advantage Actually Is — and How It Replaced Traditional Medicare
02 — The Political History: How Private Insurers Got Into Medicare
03 — The Marketing Machine: How Enrollment Works and Who It Targets
04 — Risk Adjustment: The Payment System That Rewards Diagnosis, Not Treatment
05 — The $84 Billion Overpayment: How Upcoding Works at Scale
06 — The Profit Extraction Model: What Insurers Take Before Care Is Delivered
07 — Prior Authorization in Medicare Advantage: What OIG Found
08 — The Denial and Appeals Record: What Happens When Enrollees Push Back
09 — Network Adequacy and the Coverage Gap
10 — The Extra Benefits Myth: Dental, Vision, and What the Fine Print Says
11 — When Medicare Advantage Fails: Disenrollment at the End of Life
12 — The Reform Proposals: From Audit Reform to Elimination
13 — What the Evidence Resolves — and What It Doesn’t
This article was researched and drafted with AI assistance under human review. See our full AI and editorial practices.