Carcinoembryonic Antigen — NCD 118 | CMS Coverage Update

TL;DR: The Centers for Medicare & Medicaid Services modified NCD 118 governing CEA (carcinoembryonic antigen) testing coverage, effective March 7, 2026. Here's what changes for billing teams.

CMS CEA coverage policy under NCD 118 in the Medicare system draws a tight line around when CEA testing is medically necessary — and the updated policy makes those lines clearer and, in some places, harder to cross. The policy does not list specific CPT or HCPCS codes in the current version, so your billing team needs to verify the applicable lab codes through the quarterly Covered Code Lists linked in the policy. If your practice or lab bills CEA testing for oncology patients, this update deserves a close read before the effective date of March 7, 2026.

Quick-Reference Table

CMS CEA Coverage Criteria and Medical Necessity Requirements 2026

The CMS carcinoembryonic antigen coverage policy covers CEA testing in a narrow, well-defined set of clinical situations. Medical necessity is tied to specific cancer types, treatment stages, and testing intervals. If your claim doesn't match one of those situations, expect a denial.

Here's where coverage applies:

Colorectal carcinoma follow-up is the primary covered indication. CEA testing is medically necessary for patients with colorectal carcinoma, but only at treatment decision-making points — not on a routine schedule. The American Society of Clinical Oncology (ASCO) guideline referenced in the policy recommends post-operative CEA testing every two to three months for patients with initial stage II or stage III disease. That window runs for at least two years after diagnosis, and only when resection of liver metastasis would be indicated.

Alternative marker use is covered in specific situations. When a more specific tumor marker isn't expressed by the tumor, CEA may serve as a medically necessary alternative for monitoring. The policy lists adenocarcinoma of the lung, small cell carcinoma of the lung, and certain gastrointestinal carcinomas as eligible conditions. This is an important carve-out — but note the qualifier. CEA is only appropriate as an alternative when no better marker exists for that patient's tumor.

Preoperative CEA is also covered. The policy recognizes preoperative CEA testing as useful for determining post-operative adequacy of surgical resection and guiding subsequent medical management.

Metastatic solid tumors expressing CEA represent the fourth covered scenario. For these patients, CEA may be measured at the start of treatment and with subsequent treatment cycles to assess tumor response to therapy.

One principle runs through all of these: a single tumor marker will suffice. If your team is billing multiple tumor markers alongside CEA for the same patient with colorectal carcinoma, that pattern is going to draw scrutiny. The policy is explicit that one marker generally covers the clinical need.

This coverage policy does not mention prior authorization as a requirement. That said, frequency limits are built directly into the medical necessity criteria — and those limits function like a soft prior authorization check. Claims that exceed the stated intervals will face medical necessity review.

CMS CEA Testing Exclusions and Non-Covered Indications

The policy sets firm frequency limits that define the outer edge of covered CEA billing. Go beyond these limits without documented clinical justification, and you're looking at a claim denial.

For metastatic solid tumor patients: CEA testing is generally not covered more than once per chemotherapy treatment cycle. Billing more frequently than that requires documentation of a significant change in CEA level or a significant change in patient status that could reflect disease progression or recurrence.

For post-surgical colorectal carcinoma patients: CEA testing is not covered more than once every two months. Same exception applies — significant change in status or prior results can justify more frequent testing, but you need to document that clearly in the medical record.

For in situ carcinoma: This is the tightest restriction. Testing with a diagnosis of in situ carcinoma is not covered more than once — period — unless the result is abnormal. If the result is abnormal, the test may be repeated once. That's a maximum of two tests for in situ diagnoses, and the second one requires an abnormal first result to justify it.

The real issue here is documentation. The frequency limits are clear, but the exceptions — "significant change in CEA level" or "significant change in patient status" — are clinician judgment calls. If you're billing those exceptions, the clinical note has to make that reasoning explicit. A vague note won't survive a claims audit.

Coverage Indications at a Glance

CMS CEA Billing Guidelines and Action Items 2026

CEA billing under NCD 118 in the Medicare system is manageable — but it rewards preparation. The frequency limits and indication restrictions are specific enough that billing errors here are usually preventable. Here's what to do before March 7, 2026.

If you're not sure how your current CEA billing patterns map to these criteria — especially if your practice handles a high volume of metastatic solid tumor patients — talk to your compliance officer before March 7, 2026. The frequency exception rules leave enough room for interpretation that a pre-billing audit is worth the time.

CPT, HCPCS, and ICD-10 Codes for Carcinoembryonic Antigen Under NCD 118

Covered CPT and HCPCS Codes

The NCD 118 policy document does not list specific CPT or HCPCS codes in the current version. CMS publishes a quarterly Covered Code List for clinical laboratory services that includes the applicable codes for CEA testing. Your billing team should download the current Covered Code List directly from CMS and confirm which codes apply to your claims.

Do not use codes not verified through that list. Billing an unlisted or incorrect lab code for CEA is a straightforward path to a claim denial, regardless of whether the clinical indication is covered.

Key ICD-10-CM Diagnosis Codes

The policy does not list specific ICD-10-CM codes. Based on the covered indications in the policy — colorectal carcinoma, adenocarcinoma of the lung, small cell carcinoma of the lung, gastrointestinal carcinomas, and in situ carcinoma — your coding team should confirm the appropriate diagnosis codes for each patient encounter. Pair the correct primary malignancy code with the CEA test claim, and make sure the stage documented in the record supports the indication being billed.