HCPCS Level II code C2637 represents a single non‑stranded brachytherapy source containing ytterbium‑169. This supply code is used when documenting and billing for individual radioactive seeds or sources delivered for internal radiation therapy. Its accurate use matters nationally because brachytherapy remains an important modality in cancer care and supply codes affect reimbursement, inventory tracking, and clinical documentation for radiation oncology providers.

Key payers covered in the analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of clinical context for ytterbium‑169 brachytherapy sources, typical sites of service where these sources are used, and the elements that influence coding and billing for single-source supplies. The publication also lays out common modifiers and payer considerations, benchmarking expectations where available, and recent policy developments relevant to HCPCS supply codes.

The content is intended for billing managers, radiation oncology clinicians, and revenue cycle staff seeking concise guidance on how this HCPCS Level II code is applied in practice and how payer policies can affect claim adjudication and documentation requirements.