CPT code 77778: Interstitial brachytherapy, complex source application2026 Medicare rate & RVUs in Illinois
Reports complex placement of radioactive sources within tumor tissue for interstitial brachytherapy, rather than treatment delivered through a cavity or surface applicator.
Medicare pays $888.32–$965.79 for 77778 in the office in Illinois, from Rest of Illinois to Suburban Chicago, IL. Which amount applies depends on the service address.
Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.
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On this page 9 sections
What 77778 covers
This service covers complex interstitial brachytherapy, in which radioactive sources are placed directly within or alongside tumor tissue. A radiation oncologist, often working with a procedural specialist, may perform the application in an operating room or procedure suite. Prostate seed implantation is a familiar example; interstitial techniques may also be used for selected tumors at other sites. This approach differs from delivering radiation through a cavity applicator or across the skin surface.
Report the code when the documented service is a complex interstitial source application. The record should support the interstitial approach, treated site, source placement, and complexity. CMS identifies professional and technical components: modifier 26 represents the professional interpretation, modifier TC the equipment and staff, and no modifier the global service. The 0-day global period includes same-day preoperative and postoperative care. Modifier 50 is inappropriate for this service. Assistant-at-surgery payment requires documented medical necessity; 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 77778 pays more and less in Illinois
The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.
4 payment localities
$888.32 to $965.79
| Payment locality | Office | Facility |
|---|---|---|
| Chicago, IL | $961.39 | Unavailable |
| East St. Louis, IL | $900.86 | Unavailable |
| Rest of Illinois | $888.32 | Unavailable |
| Suburban Chicago, IL | $965.79 | Unavailable |
How the 77778 rate is calculated
Each of 77778’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.
How the rate is built · 77778
RVUs × geographic indexes × conversion factor
Work8.56
8.56 RVUs× 1.000 GPCI
Practice expense18.83
18.83 RVUs× 1.000 GPCI
Malpractice0.54
0.54 RVUs× 1.000 GPCI
Adjusted RVUs
27.9300
Conversion factor
$33.4009
Medicare rate
$932.89
Every GPCI starts at 1.000, the national rate. Enter a ZIP or drag a slider.
Payment rules and modifiers for 77778
The CMS indicators that decide how 77778 is paid alongside other services.
CMS payment indicators · 77778
Interstitial brachytherapy, complex source application
| Rule | CMS value | What it means |
|---|---|---|
| Global period | 000 | Same-day global: pre- and post-op care on the day of the procedure is included. |
| Multiple procedures | 0 | No multiple-procedure reduction. |
| Bilateral (modifier 50) | 0 | The 150% bilateral adjustment doesn’t apply. |
| Assistant at surgery (80/81/82/AS) | 0 | Not paid without supporting documentation. |
| Co-surgeons (62) | 0 | Not permitted. |
| Team surgery (66) | 0 | Not permitted. |
| Professional/technical | 1 | Diagnostic test with separate professional (26) and technical (TC) components. |
What modifiers do to the payment
Modifier 26 · payment effect
With and without the modifier
77778 without 26 · national office
$932.89
Interstitial brachytherapy, complex source application
77778-26 · Professional component
$459.93
Pays only the interpretation and report.
77778 compared with similar codes
Compare codes · National
4 codes, side by side
How to choose
- 77763Brachytherapy applicationComplex intracavitary placement
- Choose 77778 for complex interstitial source placement within tissue; choose 77763 for complex application through an intracavitary applicator.
- 77770HDR brachytherapySingle channel, per fraction
- 77770 describes high-dose-rate remote afterloading. This code describes complex interstitial source application, not that remote-afterloading service.
- 77767Skin brachytherapyOne channel
- 77767 is for high-dose-rate radiation delivered at the skin surface. This code is for complex interstitial placement within tissue.
77778 billing questions
How does this differ from an intracavitary application?
This code is for complex placement of sources within tissue. Use an intracavitary application code when radiation is delivered through an applicator positioned in a body cavity.
Can the professional and technical components be billed separately?
Yes. CMS identifies modifier 26 for the professional interpretation and modifier TC for the technical service; reporting without a modifier represents the global service.
Is modifier 50 appropriate for bilateral treatment?
No. CMS identifies bilateral adjustment as inappropriate for this code, so modifier 50 should not be used.
What same-day care is included?
The 0-day global period includes same-day preoperative and postoperative care.
When may an assistant at surgery be paid?
Assistant-at-surgery payment is allowed only when the medical necessity of the assistant is documented. Co-surgeons and team surgery are not permitted.
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
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