HCPCS Code G6015: IMRT delivery billing guide (2026)

Key Takeaways

HCPCS Code G6015 describes intensity modulated radiation therapy (IMRT) delivery via binary, dynamic multi-leaf collimators (MLCs) per treatment session.

G6015 covers the technical component only and is not payable in OPPS (outpatient hospital) settings – bill in freestanding or non-facility settings only.

G6015 was deleted effective January 1, 2026; CPT codes 77385 (simple IMRT delivery) and 77386 (complex IMRT delivery) are the replacement codes for most billing contexts.

Pabau’s claims management software helps radiation oncology practices track HCPCS code transitions, documentation requirements, and claim submission rules in one place.

HCPCS Code G6015: definition and clinical description

Most radiation oncology billing denials tied to IMRT delivery come down to one of three errors: wrong setting, wrong companion code, or a failure to recognize that HCPCS Code G6015 was deleted at the start of 2026. Getting this right before a claim goes out saves significant rework downstream.

Official descriptor: Intensity modulated treatment delivery, single or multiple fields/arcs, via narrow spatially and temporally modulated beams, binary, dynamic MLC, per treatment session.

HCPCS Code G6015 was a Level II HCPCS G-code used to report the technical component of IMRT delivery when the treatment system used binary, dynamic multi-leaf collimators. Unlike fixed-field or 3D-conformal methods, binary dynamic MLC systems modulate beam intensity across narrow spatial and temporal increments, enabling highly precise dose shaping around complex tumor volumes.

The code applied per treatment session, covering single or multiple fields and arcs within the same session. It was distinct from HCPCS Code G6016, which covers compensator-based beam modulation (a different technical delivery method).

Per the CMS HCPCS overview, G-codes are temporary codes maintained by CMS for services not yet assigned a permanent CPT code or for which CMS requires a specific descriptor for program purposes. For outpatient billing workflows at freestanding radiation centers, G6015 served this function for over a decade before the 2026 deletion – as discussed in our reference on outpatient billing workflows.

OPPS setting restriction and facility vs. non-facility billing

The most consequential billing rule for HCPCS Code G6015 is its setting restriction. According to the Noridian Medicare JEA 2025 CPT/HCPCS billing and coding article, G6015 and G6016 are not payable in an OPPS (Outpatient Prospective Payment System) setting.

This means: if IMRT delivery is performed in a hospital outpatient department (place of service 22), G6015 cannot be submitted. The code covers the technical component only and is limited to freestanding radiation oncology centers or other non-facility settings.

• Non-facility (freestanding center): G6015 is billable here. Submit on the CMS-1500 claim form with appropriate place of service coding.
• Hospital outpatient (OPPS): G6015 is not payable. Use CPT 77385 or 77386 depending on complexity, billed under the facility’s outpatient claim.
• Physician professional component: IMRT delivery (G6015 or CPT 77385/77386) is a technical service. Physicians billing the professional component of IGRT add-ons use HCPCS G6001, G6002, or G6017 with a -26 modifier, as noted in ASTRO’s CT imaging guidance for IMRT.

Confusing these settings is one of the leading causes of IMRT claim denials under Medicare Part B. For specialty procedure billing codes across other oncology-adjacent specialties, the same facility-versus-non-facility distinction applies – see our reference on specialty procedure billing codes for a comparable framework.

Medicare coverage and reimbursement for HCPCS Code G6015

Medicare coverage for HCPCS Code G6015 operated under carrier judgment pricing, not a nationally published rate. This means reimbursement varied by Medicare Administrative Contractor (MAC) jurisdiction. HIPAASpace and CGS Medicare both note the “carrier priced” designation, which means practices needed to verify rates with their local MAC (such as Noridian JEA or CGS) rather than relying on a single national figure.

Coverage was contingent on medical necessity documentation per CMS Physician Fee Schedule guidelines. The relevant Local Coverage Determination was LCD L34652, which governed radiation oncology services including IMRT delivery documentation requirements.

LCD L34652’s billing and coding guidelines (the BCG PDF attachment, available from downloads.cms.gov) contained a specific rule worth noting: CPT codes 77401 and G6015 may be quantity billed on the same line of the CMS-1500 claim form. This was unusual and directly stated in the CMS guidance, so coders should reference the original LCD attachment for the specific language when auditing historical claims. For clinical coding reference on how LCDs govern claim-level documentation across specialties, the general framework is consistent.

Medicaid and state crossover claims

For Medicare/Medicaid crossover claims, Louisiana Medicaid published specific guidance covering HCPCS codes G6002 through G6015 for dates of service January 1, 2015 forward. Providers submitting crossover claims involving G6015 should consult their state Medicaid program’s crossover billing instructions, as the rules vary by state. The general principle: Medicare pays first, Medicaid pays the balance, and the HCPCS code must be recognized by both programs for the claim to process correctly.

HCPCS Code G6015 documentation requirements

CGS Medicare’s radiation oncology documentation guidelines specify what the medical record must support for a G6015 claim to pass review. The documentation standard aligns closely with LCD L34652 requirements.

Required documentation elements for HCPCS Code G6015 include:

• Treatment plan: A written IMRT treatment plan signed by the treating physician, specifying the target volume, dose prescription, number of fields/arcs, and fractionation schedule.
• Technology justification: Documentation confirming that binary dynamic MLC-based delivery was the method used (rather than compensator-based or 3D-conformal techniques).
• Diagnosis coding: An appropriate ICD-10-CM malignancy or treatment-related diagnosis code linked to the claim. The primary diagnosis must support the medical necessity of IMRT over conventional radiotherapy.
• Session log: A treatment delivery record for each session, noting the date of service, fields delivered, and machine parameters. G6015 is reported per treatment session, so session-level documentation is critical.
• Physician involvement: Evidence of physician supervision of the treatment session at the required level (for Medicare, this is direct supervision for hospital outpatient IMRT, though this does not apply since G6015 is non-facility only).

For diagnostic code documentation requirements in a non-oncology context, the same principle applies: the ICD-10 code on the claim must be supported by clinical findings in the record. In radiation oncology, the treating diagnosis is typically a primary malignancy code from ICD-10-CM Chapter 2 (C00-D49). Maintaining HIPAA-compliant documentation practices is equally important when retaining treatment session logs and physician supervision records.

NCCI bundling rules

The CMS Medicaid NCCI Policy Manual (Chapter IX, Radiology Services) directly addresses IMRT delivery codes. Per the 2022 manual: IMRT delivery (including G6015, CPT 77385, and CPT 77386) is not normally reported with treatment device design and construction codes CPT 77332 through 77334. Those codes describe the design of treatment devices for external beam and proton therapy, not IMRT delivery itself.

Similarly, IMRT delivery is reported separately from treatment planning codes (CPT 77261-77263), simulation codes (CPT 77280-77290), and port image verification (CPT 77417). Each of these represents a distinct service with its own coding and documentation requirements.

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Related HCPCS and CPT codes for IMRT delivery

Understanding HCPCS Code G6015 requires knowing how it fits within the broader radiation oncology code set. ASTRO’s CPT/HCPCS code chart organizes these by service category.

For HCPCS and ICD-10 crosswalk guidance applicable to oncology-adjacent billing scenarios, see our reference on HCPCS and ICD-10 crosswalk guidance. The AAPC HCPCS code lookup also allows coders to verify current descriptor text and deletion status for any G-code.

IGRT add-on billing rules

Image Guided Radiation Therapy (IGRT) codes (G6001, G6002, G6017) are add-on services to IMRT delivery, not separately reported as standalone services in the same session. The NCCI edits govern bundling between these codes. Per ASTRO’s coding guidance for CT image guidance:

• In a freestanding center billing G6015 (technical component): use IGRT G-codes (G6001, G6002, G6017) for the technical IGRT component.
• Physician billing the professional component: use G6001, G6002, or G6017 with a -26 modifier. Some payers also accept CPT 77387-26; verify with the specific payer before submitting.
• G6017 follows the same non-facility restriction as G6015: it may not be billed in a facility or outpatient place of service 22.

HCPCS Code G6015 deletion in 2026 and transition guidance

Multiple coding databases, including Codify by AAPC and FindACode, confirm that HCPCS Code G6015 was deleted effective January 1, 2026. The CMS NCCI Medicare Policy Manual (Chapter IX, effective January 1, 2026) references CPT codes 77385 and 77386 alongside G6015 in the context of IMRT delivery, consistent with the transition away from the G-code.

For claims with dates of service on or after January 1, 2026, coders should use:

• CPT 77385 for simple IMRT delivery (fewer beams/arcs, lower complexity).
• CPT 77386 for complex IMRT delivery (more beams/arcs, higher complexity).

For claims with dates of service prior to January 1, 2026, G6015 remains the correct code. Do not retroactively recode historical claims to CPT 77385/77386 unless a specific payer directive requires it. Historical G6015 claims that are reopened or resubmitted should use the code in effect on the date of service.

SRS bundling note for the 2026 transition

Noridian Medicare JEA’s 2025 billing update includes an important restriction for the replacement CPT codes: CPT 77385 and 77386 should not be billed in conjunction with CPT codes 77371 through 77373. Those codes cover multi-source photon (cobalt-60-based) Stereotactic Radiosurgery (SRS) planning and delivery. The IMRT delivery codes and SRS codes are mutually exclusive for the same session.

Practices transitioning from G6015 to CPT 77385/77386 should review their charge capture rules to add this exclusion logic. Managing these transitions through claims management software that flags incompatible code combinations at the point of claim creation reduces manual review burden significantly. Consistent medical documentation workflows across session logs support the audit trail that payers and MACs require when reviewing IMRT claims.

Billing workflow for HCPCS Code G6015 (historical claims)

For dates of service before January 1, 2026, the step-by-step billing process for HCPCS Code G6015 on the CMS-1500 claim form follows this sequence:

1. Confirm the delivery technology. Verify the treatment record confirms binary dynamic MLC delivery (not compensator-based, which is G6016).
2. Confirm the setting. G6015 is non-facility and freestanding only. Place of service 11 (office) or 49 (independent clinic) are typical for freestanding radiation centers. Do not submit in POS 22.
3. Assign the diagnosis code. Link an appropriate ICD-10-CM primary malignancy code (Chapter 2) or a secondary treatment-related code. The diagnosis must support IMRT necessity in the clinical documentation.
4. Check for add-ons. Determine whether IGRT was performed. If yes, add G6001, G6002, or G6017 as applicable. Apply -26 for physician professional component claims.
5. Apply the 77401 quantity rule if applicable. Per LCD L34652, CPT 77401 and G6015 may be quantity-billed on the same claim line when both apply to the session.
6. Verify against NCCI edits. Confirm no treatment device design codes (77332-77334) are on the same claim for the same session.
7. Submit and monitor. Carrier-priced codes may require follow-up with the MAC if payment is not received within standard processing windows.

The PGM Billing HCPCS lookup tool allows coders to verify G6015’s descriptor text, status, and cross-references using CMS data. This is useful when reviewing historical claims or training new coders on the pre-2026 HCPCS Code G6015 billing requirements.

Conclusion

HCPCS Code G6015 had a narrow but precise use case: IMRT delivery via binary dynamic MLC in non-facility settings, billed per treatment session under Medicare carrier-priced rules. Its deletion on January 1, 2026 moves IMRT delivery billing to CPT 77385 and 77386, but historical claims from before that date still require G6015 on resubmissions and audits.

Practices that standardize their claim workflows around code status, setting restrictions, and NCCI bundling rules reduce denial rates and accelerate reimbursement. Pabau’s claims management software supports radiation oncology teams managing code transitions, LCD documentation requirements, and MAC-specific billing rules. Book a demo to see how Pabau handles complex specialty billing workflows end-to-end.

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