CPT code 77789: Surface brachytherapy, low-dose-rate application2026 Medicare rate & RVUs

Medicare pays $132.94 for 77789 nationally in the office. Local office rates run $118.61–$177.27.

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

What 77789 covers

This service covers applying a low-dose-rate radionuclide source at a superficial treatment site using a surface applicator. A radiation oncologist typically directs the treatment, with radiation therapy staff assisting in a hospital or radiation oncology setting. The source is positioned against the target rather than placed into an interstitial tract or body cavity, distinguishing this approach from interstitial and intracavitary brachytherapy.

Select the code for the surface application method, and document the treatment site, source or applicator placement, and the physician’s work. CMS allows billing for the global service or separately for the professional interpretation with modifier 26 and the technical portion with modifier TC. Same-day preoperative and postoperative care is included in the 0-day global period. Modifier 50 is inappropriate. An assistant at surgery is paid only when medical necessity is documented; co-surgeons and team surgery are not permitted.

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 77789 pays more and less

The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.

109 of 109 payment localities

77789 rates by state

Office rate range in each state. Select a state to see its payment localities.

How the 77789 rate is calculated

Each of 77789’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 77789

The CMS indicators that decide how 77789 is paid alongside other services.

What modifiers do to the payment

When to use modifier 26

77789 compared with similar codes

How to choose

77767Skin brachytherapyOne channel

77767 describes high-dose-rate skin surface brachytherapy using one channel. Choose 77789 for low-dose-rate surface source application.

77768Skin brachytherapySurface field over 2 cm

77768 describes high-dose-rate skin surface brachytherapy using multiple channels. It is not the low-dose-rate surface application reported with 77789.

77761Intracavitary brachytherapySimple application

77761 applies when a source is placed inside a body cavity for a simple intracavitary treatment; 77789 is for a surface application.

Codes related to 77789

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