CPT 77789Radiology

Apply surf ldr radionuclide

CPT 77789 covers the application of radioactive material placed directly on the surface of a body area to treat certain conditions, typically skin lesions or superficial cancers. This is a specialized radiation therapy technique where the radioactive source is positioned on, rather than inside, the body.

Showing rates for

National Average

Base Medicare rate

$129.71

This calculator gives a typical-case estimate using standard Medicare modifier rules. Actual payment depends on payer policies, documentation, code-specific CMS status indicators, and locality. Verify before billing.

RVU breakdown

Work RVU

1.14

PE RVU (NF)

2.81

MP RVU

0.06

Total RVU

4.01

Conversion factor: 32.3465 · Source: CMS MPFS RVU25A · Confidence: High

NCCI bundling edits

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Billing tips

Document the specific radionuclide isotope used (e.g., Sr-90, P-32), activity level, application time, and exact anatomic location
Impact: Prevents 20-35% of documentation-related denials and supports medical necessity during audits
Bill 77789 only once per treatment session regardless of number of sources applied, unless treating distinctly separate anatomic sites requiring modifier 59
Impact: Avoid unbundling denials that can result in 100% claim rejection and potential compliance flags
Verify that physics consultation, treatment planning, and dosimetry calculations are separately documented and coded (77300, 77331-77334) as these are not included in 77789
Impact: Captures additional $200-$800 in legitimate reimbursement for planning services often overlooked
Ensure radiation safety officer sign-off and source accountability documentation is complete before claim submission
Impact: Critical for NRC compliance; missing documentation can delay payment 30-60 days and trigger facility audits
Submit claims within 30 days of service as radiation oncology codes face higher scrutiny during retrospective review
Impact: Timely filing improves cash flow and reduces likelihood of bundling edits being applied retroactively
For Medicare patients, verify LCD coverage for the specific diagnosis and anatomic site as surface brachytherapy has limited covered indications
Impact: Prevents 40-50% of coverage denials; consider obtaining ABN for non-covered indications averaging $129.71 patient responsibility

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Frequently asked questions

What is the Medicare reimbursement rate for CPT 77789 in 2025?

The 2025 Medicare national average reimbursement for CPT 77789 is $129.71 for both facility and non-facility settings. This rate is based on 4.01 total RVUs (1.14 work RVU, 2.81 PE RVU, 0.06 MP RVU) multiplied by the 2025 conversion factor of 32.3465.

Can CPT 77789 be billed with treatment planning codes on the same day?

Yes, treatment planning codes (77261-77263, 77295, 77300, 77331-77334) are separately billable from 77789, but planning is typically performed prior to the application date. If billed on the same date, clear documentation must demonstrate these are distinct services. Many payers require planning to be performed and billed on a separate date to avoid bundling edits.

How many times can I bill CPT 77789 for multiple lesions treated in one session?

CPT 77789 is typically billed once per treatment session. For multiple distinct lesions at separate anatomic sites treated in the same session, you may bill multiple units with modifier 59, but documentation must clearly support that each represents a separate, medically necessary treatment field requiring independent source application and planning.

What radionuclide isotopes are typically used for CPT 77789 procedures?

Common isotopes for surface brachytherapy include Strontium-90 (Sr-90) for superficial skin lesions, Phosphorus-32 (P-32), and occasionally Ruthenium-106 (Ru-106) for ophthalmic applications. The specific isotope must be documented in the medical record as it affects dosimetry calculations and radiation safety protocols.

Is CPT 77789 a facility-only code or can it be billed in office settings?

CPT 77789 has the same Medicare rate ($129.71) for both facility and non-facility settings in 2025. However, performing surface brachytherapy requires NRC or Agreement State radioactive materials licensure, which typically limits this service to hospital-based radiation oncology departments or specialized cancer centers with appropriate regulatory authorization.

What documentation is required to support medical necessity for CPT 77789?

Required documentation includes pathology confirming diagnosis, clinical rationale for surface application versus alternative treatments, tumor measurements and location, patient factors precluding other modalities, treatment intent (curative vs. palliative), radiation oncologist consultation notes, informed consent specific to brachytherapy risks, and physics calculations supporting the prescribed dose and technique.

Does CPT 77789 include the radiation source material cost?

No, CPT 77789 covers only the clinical application procedure. Radioactive source acquisition and preparation are separately reportable. Facilities typically capture source costs through revenue codes (0340-0349 for nuclear medicine/radiopharmaceuticals) or through separately billable supply codes depending on payer requirements. Check specific payer policies for source material billing.