Brachytherapy CPT Codes in Medical Billing: Code Families, Once-Per-Course Items and Site of Service

Brachytherapy CPT codes are the 77750 to 77799 series describing the application of sealed radioactive sources inside or against a tumor, grouped by route: intracavitary (77761 to 77763), interstitial (77778), high dose rate remote afterloading (77770 to 77772, by channel count) and surface (77767, 77768, 77789), with the isodose plan (77316 to 77318) and source handling (77790) alongside.

Brachytherapy claims have few lines, and most errors come from billing a line that CPT or NCCI already includes in another code.

Where you see it

Place	What goes there
CMS-1500 box 24D, freestanding center	The application code (for example 77771) and the isodose plan (77317) with no modifier
CMS-1500, physician treating a hospital patient	The same codes with modifier 26
UB-04 or 837I, hospital outpatient	The technical side of the application and plan codes, plus the source under its C-code or A-code (status U)
Medicare Physician Fee Schedule (2026)	PC/TC indicator 1 on the application and plan codes; indicator 3 (technical only) on 77790; 90-day global on 77761 to 77763
OPPS Addendum B (CY 2026)	77770 to 77772, 77763 and 77778 in APC 5624; 77761 and 77762 in APC 5623; 77316 to 77318 in APC 5612; 77790 status N; sources status U in their own APCs

The families

Code	What it describes	2026 RVUs, global
77761, 77762, 77763	Intracavitary source application: simple, intermediate, complex	12.70, 16.72, 23.71
77770	HDR remote afterloading, interstitial or intracavitary, includes basic dosimetry; 1 channel	10.46
77771	Same, 2 to 12 channels	18.29
77772	Same, more than 12 channels	27.39
77778	Interstitial source application, complex (the LDR prostate seed implant is the common case), includes supervision, handling and loading	27.93
77767, 77768	HDR skin surface brachytherapy, two levels by lesion size and channel count	7.51, 11.05
77316, 77317, 77318	Brachytherapy isodose plan: simple (1 to 4 sources, or 1 channel), intermediate, complex (over 10 sources, or over 12 channels); basic dosimetry included	7.45, 9.76, 13.86
77790	Supervision, handling and loading of the radiation source	0.56

The channel count is the number of catheters or applicator channels the afterloader treats through on that fraction: a single-channel vaginal cylinder is 77770, a tandem and ring with three channels is 77771, a fifteen-catheter interstitial implant is 77772. The isodose plan codes use parallel thresholds.

What bills once and what is bundled

The NCCI Policy Manual for Medicare, chapter 9, section F, covers most of these rules:

• 77790 is never separate from 77770 to 77772 or 77778; those codes include supervision, handling and loading.
• 77300 (basic dose calculation) is not reported with 77767 to 77772 or 77778; the calculations are integral.
• One isodose plan is one unit, however many points it calculates; the 2026 MUE for 77316 to 77318 is 1 per date of service.
• 77427, 77431 and 77336 are not reported with brachytherapy in general. If external beam runs at the same time, 77427 and 77336 are reported for the external beam fractions; for multi-step brachytherapy, 77336 may be appropriate.
• E/M visits beyond the initial consultation may be reported with 77770 to 77772 only when significant, separate and distinct from treatment management.
• 77778 is billed by the physician who applies the source. A radiation oncologist assisting a surgeon who places the catheters reports 77778 only if the oncologist applies the source at the same encounter; a source loaded later in a different room is 77770 to 77772.
• Partial breast HDR may be performed twice a day; the HDR codes carry a 2026 MUE of 2 per date.

Applicator placement is a separate event with its own surgery-section code (57155 tandem and ovoids, 57156 vaginal cylinder, 55875 prostate needles, 19296 to 19298 breast catheters, among others), billed by whoever places the device; the radiation oncologist bills the application either way.

Freestanding versus hospital

In a freestanding center the application and plan codes are billed global, with no modifier, and the center supplies the source. In a hospital department the physician bills the same codes with modifier 26, and the hospital bills the technical side under OPPS: 77770 to 77772, 77763 and 77778 in APC 5624 (Level 4 Radiation Therapy, national unadjusted 711.56), 77761 and 77762 in APC 5623 (564.51), the isodose plans in APC 5612 (382.54), and 77790 packaged (status N). Sources are paid separately to hospitals under status indicator U, each type in its own APC.

The CY 2026 OPPS final rule continued the low-volume APC policy for brachytherapy: an APC with fewer than 100 single claims in the ratesetting year is paid at the greatest of the geometric mean, arithmetic mean or median cost over up to four years of claims. For 2026 CMS designated six brachytherapy APCs as low volume (2632, 2635, 2636, 2642, 2643 and 2647); gold-198 (APC 2645) came off the list with 103 claims and non-stranded cesium-131 (APC 2643) went on with 88.

Worked example: a three-fraction HDR vaginal cuff course

A freestanding center treats a post-hysterectomy patient with a single-channel vaginal cylinder, three fractions a week apart, each insertion imaged and planned. Illustrative, 2026 national amounts before geographic adjustment (RVUs from the CMS October 2026 RVU file times 33.4009).

Line	Units	Each	Total
77263, complex clinical planning	1	168.34	168.34
77290, complex simulation (first fraction)	1	441.56	441.56
57156, cylinder insertion	3	223.79	671.37
77316, isodose plan, simple (1 channel)	3	248.84	746.52
77770, HDR, 1 channel	3	349.37	1,048.11
Course			3,075.90

Not on the claim: 77790 and 77300 (inside 77770), 77427 and 77336 (no external beam running), and 77280 for fractions two and three unless a simulation was actually repeated. In a hospital the physician bills 77770-26 (101.87) and 77316-26 (73.48) per fraction, and the hospital bills the technical lines under OPPS.

What to do

• Pick the application code by route and channel count from the treatment record for that fraction, not from the plan written the day before.
• Remove the bundled lines before you send the claim: 77790 and 77300 with any HDR or interstitial code, and 77427 or 77336 unless external beam is running at the same time.
• Bill the source on the hospital side only, with the C-code or A9527 and units equal to the number of sources; use modifier 26 for hospital patients and no modifier in the freestanding center.
• Denials to recognize: CARC 97 or CARC 236 on 77790, 77300 or 77336 billed with an HDR code, a correction rather than an appeal; CARC 151 with RARC N362 on a second isodose plan or a third HDR fraction on one date, a correction unless the record shows distinct fractions; CARC 97 on an E/M during the course, which stands unless the visit was significant and separate.
• Iridium Suite’s claim scrubber checks every service line as it is entered against CCI edits, payer rules and radiation oncology frequency rules.

Related terms

• Special treatment procedure 77470
• Continuing physics 77336 and special physics 77370
• CPT 77427
• Modifier 26 and TC
• Facility versus non-facility
• Medically unlikely edits

Further reading: CMS Medicare Claims Processing Manual, Chapter 13, section 70.4; NCCI Policy Manual for Medicare Services (chapter 9, Radiology); CMS CY 2026 OPPS final rule CMS-1834-FC and addenda; CMS PFS Relative Value Files.