Carcinoembryonic Antigen — NCD 118 | CMS Coverage Update

TL;DR: The Centers for Medicare & Medicaid Services modified NCD 118, governing CEA (carcinoembryonic antigen) tumor marker testing coverage under Medicare, effective March 7, 2026. Here's what billing teams need to know before claims go out the door.

CEA testing sits at the intersection of oncology billing and strict medical necessity documentation — and CMS just updated its coverage policy for it. NCD 118 in the CMS Medicare system defines when CEA testing is covered, how often, and for which cancer diagnoses. The policy does not list specific CPT codes in the current published version, which means your team needs to align documentation to the clinical criteria — or face claim denial. Here's what changed and what to do about it.

Quick-Reference Table

CMS CEA Tumor Marker Coverage Criteria and Medical Necessity Requirements 2026

NCD 118 is the National Coverage Determination governing Medicare coverage of carcinoembryonic antigen testing. CEA is a protein polysaccharide used as a biochemical marker to monitor how certain malignancies respond to treatment. CMS does not cover it as a general cancer screening test — only in specific clinical contexts where medical necessity is clearly established.

The CMS CEA coverage policy covers testing under four distinct scenarios. Each one has its own documentation requirements, and each one has frequency limits that can trigger a denial if you exceed them without clinical justification.

Scenario 1: Follow-up for colorectal carcinoma. CEA is medically necessary for follow-up of patients with colorectal carcinoma — but only at treatment decision-making points. That phrase matters. CMS is not covering routine surveillance testing on a fixed calendar schedule. The test needs to tie to a clinical decision.

Scenario 2: Alternative marker when a more specific marker isn't expressed. For adenocarcinoma of the lung, small cell carcinoma of the lung, and some gastrointestinal carcinomas, CEA is covered when the tumor does not express a more specific marker. Your documentation needs to reflect that the tumor's marker profile drove the decision to use CEA — not just that it's convenient or familiar.

Scenario 3: Preoperative CEA for colorectal surgery. Preoperative CEA testing is covered to help determine post-operative adequacy of surgical resection and to guide subsequent medical management. This is a well-supported indication. Document the pre-surgical context clearly.

Scenario 4: Metastatic solid tumors expressing CEA. For patients with metastatic solid tumors that express CEA, the test is covered at the start of treatment and with subsequent treatment cycles to assess the tumor's response to therapy. This is probably the highest-volume billing scenario — and the one with the tightest frequency guardrails.

The ASCO guideline referenced in the policy adds a specific post-operative monitoring recommendation: after treatment for colorectal carcinoma, when resection of liver metastasis would be indicated, test every two to three months for at least two years after diagnosis. This applies to initial stage II or stage III disease. Document the stage in the record. Missing that detail is an easy audit flag.

CEA billing does not require prior authorization under this NCD — but that doesn't mean documentation is optional. Medical necessity documentation is your defense when a claim goes to review.

CMS CEA Testing Exclusions and Non-Covered Indications

CMS draws a hard line on frequency. Exceeding these limits without documented clinical justification means your claim will not survive a review.

For metastatic solid tumors: CEA is not covered more than once per chemotherapy treatment cycle. One test per cycle is the ceiling. If you're billing more frequently, you need documented evidence of a significant change in CEA level or a significant change in patient status — specifically, evidence suggesting disease progression or recurrence.

For post-surgical colorectal carcinoma patients: Testing more often than every two months is not covered without the same clinical justification. Every two months is the baseline. More frequent testing requires a documented clinical rationale — and that rationale needs to be in the chart before the claim goes out.

For in situ carcinoma: This is the most restrictive scenario. Testing is not covered more than once unless the result is abnormal. If the result is abnormal, CMS allows one repeat test. That's it. Two tests maximum under this indication, and only one if the first result is normal.

CEA used as a general cancer screening tool — without a confirmed malignancy and without a specific monitoring rationale — is not covered. The real issue here is that some practices order CEA reflexively without tying it to a treatment decision point. That's where denials accumulate.

Coverage Indications at a Glance

CMS CEA Billing Guidelines and Action Items 2026

The effective date of March 7, 2026 means claims for dates of service on or after that date are subject to this updated coverage policy. Here's what your team needs to do now.

CPT, HCPCS, and ICD-10 Codes for CEA Testing Under NCD 118

A Note on Code Coverage

NCD 118, as published with this March 7, 2026 modification, does not include a specific list of CPT, HCPCS, or ICD-10 codes. This is not unusual for older NCDs — CMS sometimes publishes covered code lists separately on a quarterly basis.

The policy cross-references the Medicare Claims Processing Manual, Chapter 120, for Clinical Laboratory Services. It also notes that Covered Code Lists, including narrative descriptions, are published quarterly and linked from the NCD page.

Your action item: Pull the current quarterly Covered Code List from the NCD 118 source page at CMS before billing. Do not assume the codes from a prior quarter's list are still current. CEA testing is typically billed under a laboratory CPT code for tumor marker quantitation — your lab billing team will know the specific code — but verify against the CMS quarterly list before submitting.

Do not bill a code that does not appear on the current Covered Code List. That is a fast path to a claim denial and potential reimbursement clawback.