Summary & Overview

HCPCS Level II J9358: Injection, fam-trastuzumab deruxtecan-nxki, 1 mg

HCPCS Level II code J9358 identifies the drug product fam-trastuzumab deruxtecan-nxki, billed at a unit of 1 mg for intravenous administration. This antineoplastic antibody-drug conjugate is used in oncology care and is significant nationally due to its high per-unit cost, impact on specialty drug spending, and implications for site-of-service billing practices. Major payers included in this analysis are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will learn what the code represents clinically and operationally, which payers cover use of the product, and how billing and coding for the drug typically appear on claims. The publication provides benchmarks for unit-based billing, notes common sites of administration (infusion centers, outpatient hospital clinics, and physician offices), and summarizes relevant policy or coverage considerations affecting reimbursement and prior authorization workflows. Data not available in the input are explicitly noted where applicable.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareJ9358HCPCS Level IIantineoplasticinfusionfam-trastuzumab deruxtecandrug billingoncolyticsunit dosingoutpatient infusion

Billing Code Overview

HCPCS Level II code J9358 represents injection of fam-trastuzumab deruxtecan-nxki, billed per 1 mg of drug. This code covers administration of the antibody-drug conjugate indicated for oncology treatment.

Service type: Drug administration (antineoplastic injection)
Typical site of service: Infusion center, outpatient hospital clinic, or physician office-based infusion suite

Clinical & Coding Specifications

Clinical Context

A 55-year-old female with previously treated HER2-positive metastatic breast cancer presents to the oncology infusion center for administration of fam-trastuzumab deruxtecan-nxki. The prescribing oncologist has determined the patient remains an appropriate candidate for antibody–drug conjugate therapy based on tumor HER2 expression and prior lines of therapy. The clinical workflow includes pre-infusion evaluation (vital signs, review of recent labs including complete blood count and liver function tests), verification of medication dose and lot, preparation of J9358 (fam-trastuzumab deruxtecan-nxki) by pharmacy under sterile conditions, patient consent and allergy review, administration via intravenous infusion by an oncology nurse, monitoring for infusion-related reactions during and for a period after infusion, and documentation of dose (mg) and lot number in the medical record. Billing captures the administered units of J9358 billed per 1 mg increment, associated infusion encounter CPT codes for infusion time and drug administration, and any applicable modifier(s) reflecting circumstances such as bilateral procedures, mechanical complications, or medical necessity adjustments.

Coding Specifications

Modifier	Description	When to Use
`JW`	Drug discarded/partial dose	When part of a single-use vial is discarded and payer requires reporting of wasted drug units.
`JZ`	No drug waste/entire vial administered	When the entire drug vial(s) were administered with no waste.
`62`	Two surgeons	Rarely used; if two physicians of different specialties share primary responsibility for an associated invasive procedure during the same encounter.
`78`	Unplanned return to the OR	If an unplanned operative intervention related to infusion complications occurs during the global period.
`80`	Assistant surgeon	When an assistant surgeon participates in a related procedure requiring surgical assistance.
`82`	Assistant surgeon (when qualified resident not available)	When an assistant surgeon is required and a resident is not available.
`23`	Unusual anesthesia	When unusually extensive or prolonged anesthesia is required for a related invasive procedure.
`25`	Significant, separately identifiable E/M on same day	When a significant evaluation and management service is provided on the same day as the infusion and must be reported separately.
`52`	Reduced services	When the service performed is partially reduced or eliminated at the physician’s discretion.
`53`	Discontinued procedure	When a planned procedure is started but discontinued due to extenuating circumstances, e.g., severe infusion reaction requiring termination.
`59`	Distinct procedural service (Note: not listed in input modifiers)	Data not available in the input.
`CP`	Example not applicable	Data not available in the input.

Taxonomy Code	Specialty	Notes
`207Q00000X`	Medical Oncology	Primary prescribing and management specialty for systemic cancer therapy.
`207RN0400X`	Hematology-Oncology	Combined specialty frequently administering targeted cytotoxic conjugates.
`363LF0000X`	Clinical Pharmacology	Pharmacists involved in dosing, compounding, and drug safety oversight in infusion centers.
`363A00000X`	Ambulatory Infusion Nurse	Nursing specialty that administers IV oncology therapies in outpatient settings.
`207L00000X`	Surgical Oncology	Occasionally involved when coordination with surgical treatment or ports is required.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`C50.911`	Malignant neoplasm of unspecified site of right female breast	HER2-positive breast cancer is a primary indication for fam-trastuzumab deruxtecan-nxki in metastatic or unresectable disease.
`C50.912`	Malignant neoplasm of unspecified site of left female breast	Left-sided breast cancer with HER2 overexpression can be treated with targeted antibody–drug conjugates.
`C79.51`	Secondary malignant neoplasm of bone	Metastatic spread (e.g., bone metastases) commonly coexists in patients receiving systemic HER2-targeted therapy.
`C78.7`	Secondary malignant neoplasm of liver and intrahepatic bile duct	Hepatic metastases are a frequent site of breast cancer spread and influence systemic therapy choice and monitoring.
`Z85.3`	Personal history of malignant neoplasm of breast	Documented history when delivering ongoing systemic therapy for recurrent or metastatic disease.
`C50.919`	Malignant neoplasm of unspecified site of unspecified female breast	Used when laterality or exact subsite is unspecified while indicating active breast malignancy.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`96413`	Chemotherapy administration, intravenous infusion technique; each additional hour (List separately in addition to primary service)	Used for documenting extended infusion time beyond the first hour when `J9358` infusion requires prolonged infusion or monitoring.
`96415`	Chemotherapy administration, intravenous infusion technique; each additional subsequent hour	Billed for subsequent additional hours of infusion beyond those reported with primary infusion codes.
`96417`	Chemotherapy administration, intravenous infusion technique, hourly; each additional hour (if applicable)	Used in some billing scenarios to capture incremental infusion hours when applicable.
`96401`	Chemotherapy administration, subcutaneous or intramuscular; non-hormonal anti-neoplastic	Billed rarely; generally not applicable to intravenous fam-trastuzumab deruxtecan-nxki but included for related chemo administration services.
`96422`	Chemotherapy administration, intravenous infusion, for initiation of a new drug or regimen (requiring complex care)	Used when initial infusion requires complex care or observation during regimen initiation.