2026 ICD-10-CM Diagnosis Code Z51.0Encounter for antineoplastic radiation therapy

ICD-10-CM Codes›Z00–Z99›Z40-Z53›Z51

ICD-10-CM Z51.0
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Z51.0 is a billable ICD-10-CM diagnosis code for encounter for antineoplastic radiation therapy. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 826 through 830. The code is exempt from POA reporting. Coders also document this condition as chemotherapy AND/OR radiation therapy prior to lymphadenectomy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Encounter for antineoplastic therapies.

Code Identity

ICD-10-CM Code
Z51.0
Billable Status
Yes — Valid for Submission
Code Describes
Encounter for antineoplastic radiation therapy
Short Description
Encounter for antineoplastic radiation therapy
Same as the full description in the CMS dataset.
Parent Code
Z51
Encounter for other aftercare and medical care

Code Classification

ChapterZ00–Z99Factors influencing health status and contact with health services
SectionZ40-Z53Encounters for other specific health care
CategoryZ51Encounter for other aftercare and medical care
This CodeZ51.0Encounter for antineoplastic radiation therapy

Present on Admission (POA)Billing

Z51.0 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chemotherapy AND/OR radiation therapy prior to lymphadenectomy
  • Radiotherapy started

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Admission(for)
      • aftercare
        • radiation therapy (antineoplastic)
    • Admission(for)
      • radiation therapy (antineoplastic)
    • Encounter(with health service) (for)
      • radiation therapy (antineoplastic)
    • Maintenance(encounter for)
      • antineoplastic radiation therapy
    • Radiation
      • therapy, encounter for
    • Radiotherapy session

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR FAC006
Encounter for antineoplastic therapies
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Radiation Therapy

Radiation therapy is a cancer treatment. It uses high doses of radiation to kill cancer cells and stop them from spreading. It may also be used for easing cancer symptoms. Radiation therapy may damage healthy cells. They can usually repair themselves more easily than cancer cells.

The full article covers:

  • What is radiation therapy?
  • When is radiation therapy used for cancer treatment?
  • How is radiation therapy given?
  • What are the side effects of radiation therapy?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert Z51.0 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
V58.0 Radiotherapy encounter
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Z51.0Overview

Is Z51.0 (Encounter for other aftercare and medical care) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report encounter for antineoplastic radiation therapy on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does Z51.0 group to?

When encounter for antineoplastic radiation therapy is the principal diagnosis on an inpatient stay, it groups to MS-DRG 826, 827, 828, 829, 830, with relative weights from 1.5050 to 4.6778 depending on complications. Higher weights mean higher Medicare reimbursement.

Is Z51.0 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for encounter for antineoplastic radiation therapy on inpatient claims.

What is the ICD-9 equivalent of Z51.0?

Under the General Equivalence Mappings, encounter for antineoplastic radiation therapy converts to ICD-9-CM V58.0 (radiotherapy encounter). The mapping is a direct match.