HCPCS code J9358: Fam-trastuzumab deruxtecan, per 1 mg2026 Medicare rate & RVUs in Washington

CMS doesn’t publish an office rate for J9358 in Washington.

Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.

What J9358 covers

Fam-trastuzumab deruxtecan-nxki, marketed as Enhertu, is an intravenous antibody-drug conjugate used in oncology. It combines a HER2-targeting antibody with a cytotoxic drug. Oncology practices administer it by infusion for selected breast, gastric or gastroesophageal junction, and lung cancers, based on the cancer type and tumor features. The treating oncology team reports the drug under J9358; a separate chemotherapy administration service may also be reported when applicable.

J9358 is a Part B drug code, with each unit representing 1 mg of fam-trastuzumab deruxtecan-nxki. Medicare excludes it from the physician fee schedule (status E); when Medicare covers it, payment is generally made under the Part B drug method using CMS quarterly ASP drug pricing files. Coverage is left to the Medicare contractor’s judgment. Report units based on the administered dose in milligrams.

This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.

Where J9358 pays more and less in Washington

How the J9358 rate is calculated

Each of J9358’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.

Payment rules and modifiers for J9358

J9358 has no global surgery period, no multiple-procedure, bilateral or assistant-at-surgery adjustment, and no professional/technical split. What changes the payment is where the service happens: the place of service on the claim decides whether Medicare pays the office or the facility rate.

J9358 compared with similar codes

How to choose

J9354Ado-trastuzumab emtansinePer 1 mg

J9354 identifies ado-trastuzumab emtansine, a different HER2-directed antibody-drug conjugate. Use J9358 only when fam-trastuzumab deruxtecan-nxki is the product administered.

J9355Trastuzumab injectionPer 10 mg, non-biosimilar

J9355 identifies trastuzumab, not fam-trastuzumab deruxtecan-nxki. The products have different drug identities and are not interchangeable code choices.

J9356Trastuzumab combinationPer 10 mg trastuzumab

J9356 identifies a subcutaneous trastuzumab and hyaluronidase product. J9358 identifies the distinct intravenous fam-trastuzumab deruxtecan-nxki product.

Codes related to J9358

Related codes aren’t interchangeable: bill the code that matches the service performed.

Where these rates come from

FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.

CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027

Open CMS sourceHow we calculate rates