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CPT 77437: Surface Radiation Therapy (Superficial) Per Fraction

CPT code 77437 represents a single fraction of surface radiation therapy (SRT) using X rays of 150 kV or less, commonly applied to superficial skin cancers and lesions. The code captures a distinct, shallow-penetration therapeutic modality that is clinically relevant for dermatologic oncology and selected outpatient radiation treatments. Nationally, accurate coding for 77437 affects coverage determinations, site-of-service classification, and procedure-level utilization tracking for superficial radiation therapy.

Key payers in this review include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical context for superficial radiation, expected sites of service, and what is typically captured by this per-fraction CPT code. The publication also summarizes benchmark considerations, payer coverage patterns, and any notable policy or billing guidance available for SRT billing at a national level.

This piece is intended to help coders, billing managers, and policy analysts understand the purpose of CPT code 77437, how it is used in clinical settings, and where it fits in the landscape of radiation therapy services. Data not available in the input.

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Billing Code Overview

CPT code 77437 describes delivery of surface radiation therapy (SRT) using X rays of ≤150 kilovoltage (kV) energy for a single treatment session (per fraction). This technique, often called superficial radiation, is used to treat skin cancers and superficial lesions where radiation penetration is typically less than 1.5 to 2.0 cm.

Service type: Surface radiation therapy (superficial radiation) — per fraction

Typical site of service: Outpatient radiation oncology clinic or dermatology practice procedure suite providing superficial radiation treatments

Data not available in the input.

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CPT 77437: Surface Radiation Therapy (Superficial) Per Fraction

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Billing Code Overview

Service type: Surface radiation therapy (superficial radiation) — per fraction

Typical site of service: Outpatient radiation oncology clinic or dermatology practice procedure suite providing superficial radiation treatments

Data not available in the input.

Clinical & Coding Specifications

Clinical Context

A typical patient is an adult with a superficial skin malignancy such as a basal cell carcinoma or squamous cell carcinoma limited to the epidermis and superficial dermis on a sun-exposed area (for example, the nose, cheek, forehead, scalp, or hand). The patient is evaluated in a dermatology or radiation oncology clinic where the lesion is documented, photographed, and measured. A biopsy confirming the diagnosis is available and discussed. Surface radiation therapy using low-energy X-rays (superficial radiation therapy) is selected when the lesion depth is generally less than 1.5–2.0 cm, when surgical excision may cause unacceptable cosmetic or functional deficit, or when the patient prefers a non‑surgical option.

The clinical workflow includes pre-treatment planning with lesion mapping and field marking, immobilization as needed, selection of applicator size and energy (≤150 kV), and documentation of fractionation and dose. Each treatment session is billed per fraction using 77437. Treatment is typically delivered in a clinic-based procedure room or outpatient radiation therapy suite with appropriate shielding and safety protocols. Follow-up includes wound care instructions, skin reactions monitoring, and periodic surveillance for recurrence.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the physician's interpretive or professional portion if the facility bills separately.
`TC`	Technical component	Use when billing only the facility/technical portion of the service.
`59`	Distinct procedural service	Use when a separate, distinct surface radiation field or unrelated procedure is performed on the same day and documentation supports distinct services.
`79`	Unrelated procedure or service by same physician during postoperative period	Use when a separate, unrelated treatment session is delivered during a global postoperative period.
`24`	Unrelated evaluation and management service during postoperative period	Use when an E/M visit unrelated to the radiation therapy is provided during a global period.
`25`	Significant, separately identifiable E/M service on the same day	Use when a significant E/M service is performed the same day as `77437` and is documented separately.
`GA`	Waiver of liability statement on file (advance beneficiary notice)	Use when the patient signs an ABN/waiver for potential noncoverage.
`GZ`	Item/service expected to be denied as not reasonable and necessary — no ABN on file	Use when the service is furnished and no ABN is on file and denial is expected.
`52`	Reduced services	Use when a reduced dose or abbreviated procedure is performed and the charge is reduced accordingly.
`RT`	Right side	Use to identify laterality when applicable for separate lesions on distinct anatomic sites.
`LT`	Left side	Use to identify laterality when applicable for separate lesions on distinct anatomic sites.

Taxonomy Code	Specialty	Notes
`2084P0800X`	Dermatology	Dermatologists commonly evaluate and deliver or coordinate SRT for superficial skin cancers.
`2086S0102X`	Radiation Oncology	Radiation oncologists direct treatment planning and delivery of superficial radiation therapy.
`207R00000X`	Family Medicine	Family physicians may refer, provide initial evaluation, or deliver in limited settings where credentialed.
`363L00000X`	Plastic Surgery	Plastic surgeons participate when reconstruction planning or cosmetic outcomes are a focus.
`208000000X`	Internal Medicine	Internists may co-manage medical issues and coordinate care, though they rarely deliver SRT directly.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`C44.311`	Basal cell carcinoma of right cheek	BCC is a common superficial skin cancer treated with `77437` when superficial radiation is chosen.
`C44.312`	Basal cell carcinoma of left cheek	Laterality variants describe lesion site for coding and treatment planning.
`C44.119`	Squamous cell carcinoma of skin of face, unspecified	SCC of the face may be treated with superficial radiation when surgery is not preferred.
`C44.219`	Squamous cell carcinoma of skin of scalp and neck, unspecified	Superficial lesions of scalp/neck that are shallow can be treated with `77437`.
`D04.9`	Carcinoma in situ of skin, unspecified	In situ lesions may be appropriate for superficial radiation depending on location and patient factors.
`L57.0`	Actinic keratosis	Premalignant lesions sometimes treated with local destruction or, less commonly, considered in the spectrum of surface treatments.
`Z85.820`	Personal history of malignant neoplasm of skin	Relevant to planning surveillance and decisions regarding SRT.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`17000`	Destruction (eg, laser surgery, electrosurgery, cryosurgery, chemosurgery, surgical curettement), premalignant lesion (eg, actinic keratosis); first lesion	Performed prior to or instead of `77437` for superficial premalignant lesions or when destruction is chosen instead of SRT.
`11102`	Tangential biopsy of skin, single lesion	Diagnostic procedure used to obtain tissue for histologic confirmation before planning `77437`.
`11600`	Excision, malignant lesion including margins, trunk, arms or legs; excised diameter 0.5 cm or less	Surgical alternative to SRT; documented when surgery is performed instead of or prior to radiation.
`77261`	Therapeutic radiology treatment planning; simple	Used when formal radiation therapy planning is required for SRT delivery workflows.
`77432`	Therapeutic radiology simulation-aided field setting; simple	Simulation or field setup services that may be performed as part of preparing for `77437` treatments.

CPT 77427: Radiation Therapy Management, External Beam

CPT-77431-RADIOTHERAPY-MANAGEMENT-ONE-TWO-FRACTION-COURSE

CPT 77431: Radiotherapy Management for One- or Two-Fraction Courses

CPT-77432-SINGLE-SESSION-STEREOTACTIC-RADIOSURGERY-PROFESSIONAL

CPT 77432: Single-Session Stereotactic Radiosurgery, Professional Component

CPT-77435-STEREOTACTIC-BODY-RADIOTHERAPY-TREATMENT-MANAGEMENT

CPT 77435: Stereotactic Body Radiotherapy Treatment Management

CPT-77438-ORTHOVOLTAGE-SURFACE-RADIATION-THERAPY-SINGLE-FRACTION

CPT 77438: Orthovoltage Surface Radiation Therapy, Single Fraction

CPT-77439-ULTRASOUND-GUIDED-SRT-FIELD-PLACEMENT

CPT 77439: Ultrasound Guidance for Surface Radiation Therapy Field Placement

CPT-77469-INTRAOPERATIVE-RADIATION-THERAPY-IORT-DURING-SURGERY

CPT 77469: Intraoperative Radiation Therapy during Surgery

CPT-77470-SPECIAL-RADIOTHERAPY-MANAGEMENT

CPT 77470: Special Radiotherapy Procedure Management

CPT-77499-UNLISTED-THERAPEUTIC-RADIOLOGY-TREATMENT-MANAGEMENT

CPT 77499: Unlisted Therapeutic Radiology Treatment Management

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Jul 29, 2026.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.

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Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

Trek Health ingests and normalizes Transparency in Coverage data and payer policy updates to give provider organizations a clear view of how commercial reimbursement behaves across markets, payers, and services. Our platform transforms raw payer disclosures into structured intelligence that supports contract evaluation, payer negotiations, and service line strategy. By combining market benchmarks with ongoing policy visibility, Trek helps teams identify variability, risk, and opportunity in commercial reimbursement. The result is faster insight, stronger negotiating positions, and more informed financial decisions.

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the physician's interpretive or professional portion if the facility bills separately.
`TC`	Technical component	Use when billing only the facility/technical portion of the service.
`59`	Distinct procedural service	Use when a separate, distinct surface radiation field or unrelated procedure is performed on the same day and documentation supports distinct services.
`79`	Unrelated procedure or service by same physician during postoperative period	Use when a separate, unrelated treatment session is delivered during a global postoperative period.
`24`	Unrelated evaluation and management service during postoperative period	Use when an E/M visit unrelated to the radiation therapy is provided during a global period.
`25`	Significant, separately identifiable E/M service on the same day	Use when a significant E/M service is performed the same day as `77437` and is documented separately.
`GA`	Waiver of liability statement on file (advance beneficiary notice)	Use when the patient signs an ABN/waiver for potential noncoverage.
`GZ`	Item/service expected to be denied as not reasonable and necessary — no ABN on file	Use when the service is furnished and no ABN is on file and denial is expected.
`52`	Reduced services	Use when a reduced dose or abbreviated procedure is performed and the charge is reduced accordingly.
`RT`	Right side	Use to identify laterality when applicable for separate lesions on distinct anatomic sites.
`LT`	Left side	Use to identify laterality when applicable for separate lesions on distinct anatomic sites.

Taxonomy Code	Specialty	Notes
`2084P0800X`	Dermatology	Dermatologists commonly evaluate and deliver or coordinate SRT for superficial skin cancers.
`2086S0102X`	Radiation Oncology	Radiation oncologists direct treatment planning and delivery of superficial radiation therapy.
`207R00000X`	Family Medicine	Family physicians may refer, provide initial evaluation, or deliver in limited settings where credentialed.
`363L00000X`	Plastic Surgery	Plastic surgeons participate when reconstruction planning or cosmetic outcomes are a focus.
`208000000X`	Internal Medicine	Internists may co-manage medical issues and coordinate care, though they rarely deliver SRT directly.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`C44.311`	Basal cell carcinoma of right cheek	BCC is a common superficial skin cancer treated with `77437` when superficial radiation is chosen.
`C44.312`	Basal cell carcinoma of left cheek	Laterality variants describe lesion site for coding and treatment planning.
`C44.119`	Squamous cell carcinoma of skin of face, unspecified	SCC of the face may be treated with superficial radiation when surgery is not preferred.
`C44.219`	Squamous cell carcinoma of skin of scalp and neck, unspecified	Superficial lesions of scalp/neck that are shallow can be treated with `77437`.
`D04.9`	Carcinoma in situ of skin, unspecified	In situ lesions may be appropriate for superficial radiation depending on location and patient factors.
`L57.0`	Actinic keratosis	Premalignant lesions sometimes treated with local destruction or, less commonly, considered in the spectrum of surface treatments.
`Z85.820`	Personal history of malignant neoplasm of skin	Relevant to planning surveillance and decisions regarding SRT.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`17000`	Destruction (eg, laser surgery, electrosurgery, cryosurgery, chemosurgery, surgical curettement), premalignant lesion (eg, actinic keratosis); first lesion	Performed prior to or instead of `77437` for superficial premalignant lesions or when destruction is chosen instead of SRT.
`11102`	Tangential biopsy of skin, single lesion	Diagnostic procedure used to obtain tissue for histologic confirmation before planning `77437`.
`11600`	Excision, malignant lesion including margins, trunk, arms or legs; excised diameter 0.5 cm or less	Surgical alternative to SRT; documented when surgery is performed instead of or prior to radiation.
`77261`	Therapeutic radiology treatment planning; simple	Used when formal radiation therapy planning is required for SRT delivery workflows.
`77432`	Therapeutic radiology simulation-aided field setting; simple	Simulation or field setup services that may be performed as part of preparing for `77437` treatments.

CPT 77427: Radiation Therapy Management, External Beam

CPT-77431-RADIOTHERAPY-MANAGEMENT-ONE-TWO-FRACTION-COURSE

CPT 77431: Radiotherapy Management for One- or Two-Fraction Courses

CPT-77432-SINGLE-SESSION-STEREOTACTIC-RADIOSURGERY-PROFESSIONAL

CPT 77432: Single-Session Stereotactic Radiosurgery, Professional Component

CPT-77435-STEREOTACTIC-BODY-RADIOTHERAPY-TREATMENT-MANAGEMENT

CPT 77435: Stereotactic Body Radiotherapy Treatment Management

CPT-77438-ORTHOVOLTAGE-SURFACE-RADIATION-THERAPY-SINGLE-FRACTION

CPT 77438: Orthovoltage Surface Radiation Therapy, Single Fraction

CPT-77439-ULTRASOUND-GUIDED-SRT-FIELD-PLACEMENT

CPT 77439: Ultrasound Guidance for Surface Radiation Therapy Field Placement

CPT-77469-INTRAOPERATIVE-RADIATION-THERAPY-IORT-DURING-SURGERY

CPT 77469: Intraoperative Radiation Therapy during Surgery

CPT-77470-SPECIAL-RADIOTHERAPY-MANAGEMENT

CPT 77470: Special Radiotherapy Procedure Management

CPT-77499-UNLISTED-THERAPEUTIC-RADIOLOGY-TREATMENT-MANAGEMENT

CPT 77499: Unlisted Therapeutic Radiology Treatment Management

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Jul 29, 2026.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

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CPT 77437: Surface Radiation Therapy (Superficial) Per Fraction

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Billing Code Overview

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CPT 77437: Surface Radiation Therapy (Superficial) Per Fraction

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Billing Code Overview

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References