G9835 Trastuzumab — HCPCS Reimbursement

HCPCS Level II code G9835 documents administration of trastuzumab within 12 months of a cancer diagnosis. The code captures a time-sensitive, guideline-aligned component of HER2-positive cancer treatment and is relevant to quality measurement, oncology care coordination, and payer coverage determinations. Nationally, accurate reporting of this service code supports performance tracking for timely initiation of HER2-targeted therapy and can affect quality metrics and population-level treatment monitoring.

Key payers in the analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. The publication outlines how G9835 is used in claims, its clinical context as an infusion/chemotherapy administration in outpatient infusion centers or hospital outpatient departments, and where it fits within treatment timelines for HER2-positive disease.

Readers will find: benchmark context for timely trastuzumab initiation, policy and coverage considerations affecting outpatient oncology billing, and operational points for coding and documentation where available. Data not available in the input is noted where applicable. The content is intended for national audiences including payers, providers, and health policy stakeholders seeking concise guidance on the role and reporting of HCPCS Level II code G9835 in oncology care delivery.

Billing Code Overview

HCPCS Level II code G9835 represents trastuzumab administered within 12 months of diagnosis. This code describes the delivery of the targeted anti-HER2 monoclonal antibody trastuzumab as part of a patient's oncology treatment plan within the first year after diagnosis.

Service type: Infusion/chemotherapy administration
Typical site of service: Outpatient infusion center or hospital outpatient department

Data not available in the input.

Clinical Context

A typical patient is a woman recently diagnosed with HER2-positive invasive breast cancer who receives adjuvant or neoadjuvant targeted therapy. The clinical workflow begins with diagnosis (imaging and biopsy with HER2 testing). After surgical planning or prior to surgery for neoadjuvant intent, the oncology team prescribes trastuzumab. Administration of G9835 documents that trastuzumab was given within 12 months of diagnosis. Treatment is typically delivered in an outpatient oncology infusion center, hospital outpatient department, or physician office by an oncology nurse under supervision of a medical oncologist or infusion-capable surgeon. Before each dose, the patient receives an assessment for cardiac risk (history, baseline and periodic echocardiography or MUGA), vital signs, and review of concurrent chemotherapy agents. Infusion ordering, pharmacy preparation, administration record, and documentation of date and dose are captured in the medical record. Billing uses G9835 to indicate trastuzumab was administered within 12 months of diagnosis for quality measurement and claims reporting; concurrent CPT and drug J-codes (for the drug product) are billed per payer rules.

Coding Specifications

Modifier	Description	When to Use
`22`	Increased procedural services	Use when work, time, or complexity of infusion encounter is substantially greater than typical (e.g., significant additional monitoring or prolonged infusion due to reaction).

Taxonomy Code	Specialty	Notes
`207RP1001X`	Medical Oncology	Primary specialty responsible for trastuzumab prescribing and infusion oversight.
`363A00000X`	Hematology-Oncology	Specialists who manage systemic therapy protocols including trastuzumab.
`207BA0003X`	Surgical Oncology	Surgeons who coordinate neoadjuvant or adjuvant systemic therapy with operative care.
`367A00000X`	Infusion Nursing	Nurses and infusion clinic staff who administer and document trastuzumab infusions.
`207Q00000X`	Oncology Nurse Practitioner	Advanced practice clinicians who assess, prescribe, and manage infusion therapy.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`C50.911`	Malignant neoplasm of unspecified site of right female breast	Breast cancer diagnosis commonly associated with HER2-targeted therapy dosing and timing within 12 months of diagnosis.
`C50.912`	Malignant neoplasm of unspecified site of left female breast	Left-sided breast cancer requiring systemic therapy including trastuzumab for HER2-positive tumors.
`C50.919`	Malignant neoplasm of unspecified site of breast, unspecified laterality	Used when laterality unspecified; entry for patients receiving trastuzumab within guideline windows.
`C50.129`	Malignant neoplasm of central portion of left female breast	Specific breast cancer sites that may receive trastuzumab as adjuvant or neoadjuvant therapy.
`C50.111`	Malignant neoplasm of central portion of right female breast	Right-sided tumor examples for trastuzumab treatment when HER2 positive.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`96365`	Intravenous infusion, initial, up to 1 hour	Used for the initial infusion encounter when trastuzumab is administered as a separate intravenous therapeutic infusion.
`96366`	Intravenous infusion, each additional hour	Billed when the infusion time for trastuzumab exceeds the initial hourly unit and additional hours are documented.
`96413`	Chemotherapy administration, intravenous infusion technique; each additional sequential infusion (up to 1 hour)	Used when trastuzumab is administered as part of multiple sequential chemotherapeutic agents during the same visit.
`36415`	Collection of venous blood by venipuncture	Often performed before or during the infusion visit for labs such as complete blood count or basic metabolic panel.
`93000`	Electrocardiogram, routine ECG with at least 12 leads; with interpretation and report	Performed periodically to evaluate cardiac status before or during trastuzumab therapy as part of cardiac monitoring protocols.

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Summary & Overview

HCPCS G9835: Trastuzumab Administered Within 12 Months of Diagnosis