Summary & Overview
HCPCS C9455: Injection, siltuximab, 10 mg
HCPCS Level II code C9455 denotes a 10 mg unit of siltuximab administered by injection. Siltuximab is a monoclonal antibody used in certain oncologic and inflammatory indications; capturing its use precisely in billing systems matters for clinical documentation, coverage determination, and national expenditure tracking. Accurate coding supports claims adjudication and reporting of biologic therapy utilization across outpatient infusion settings.
Key national payers included in this overview are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. The summary presents payer coverage considerations, typical sites of service, and the clinical context for use of C9455.
Readers will learn what the code represents, where the service is typically delivered, and which major payers are relevant to reimbursement discussions. The publication also outlines expected benchmarks and policy topics readers should review when managing claims for siltuximab, and it highlights areas where data was not provided in the input. Data not available in the input is clearly noted where applicable.
Billing Code Overview
HCPCS Level II code C9455 describes an injection of siltuximab, dosed as 10 mg per listed unit. The code represents a billed service for administration of the monoclonal antibody siltuximab.
Service type: Injection / Parenteral Therapeutic Administration
Typical site of service: Outpatient infusion or oncology clinic, where intravenous or parenteral biologic therapies are administered.
Data not available in the input.
Clinical & Coding Specifications
Clinical Context
A typical patient is an adult with multicentric Castleman disease (MCD) or symptomatic plasma cell variant of Castleman disease referred to an outpatient infusion center or hospital outpatient department for intravenous administration of C9455 (siltuximab) dosed per weight. The clinical workflow begins with hematology/oncology evaluation confirming diagnosis, review of prior therapies and laboratory baseline (CBC, CMP, liver function tests, CRP, and viral hepatitis screening). The provider documents indication, dosing calculation (e.g., 11 mg/kg every 3 weeks as commonly used for MCD), and obtains informed consent. On infusion day, infusion nursing verifies identity, reviews pre-medications and allergy history, obtains baseline vital signs, and starts IV access. Siltuximab is prepared by pharmacy per institutional protocols and administered intravenously over the recommended infusion time with monitoring for infusion reactions. Post-infusion vitals are recorded and the patient is observed for any delayed reactions. Follow-up visits include interval assessment of symptoms, physical exam, labs for treatment response and toxicity, and documentation of subsequent administrations until therapy completion or transition to alternative therapy. Typical sites of service are outpatient infusion centers, hospital outpatient departments, or physician office infusion suites for specialty oncology care.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
25 | Significant, separately identifiable evaluation and management service by the same physician on the day of a procedure |