CPT Code 77336: Continuing medical physics consultation

CPT Code 77336 is the billing code for continuing medical physics consultation, reported once per week of radiation therapy. A qualified medical physicist performs the service in person while the patient is under treatment.

The weekly note has to cover assessment of treatment parameters, quality assurance of dose delivery, and review of the patient’s treatment documentation.

The code is technical-component-only, so there is no professional component and no modifier 26 option. Bill it only for weeks in which fractions were delivered. Treatment breaks and holiday weeks do not qualify.

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Key takeaways

CPT Code 77336 covers continuing medical physics consultation, billed once per week of radiation therapy.

A qualified medical physicist has to personally assess treatment parameters, dose delivery quality assurance, and treatment documentation each billed week.

The code is technical-component-only, so modifier 26 and a professional or global split never apply.

A missing physicist signature, or a week with no treatment delivered, is the most common audit trigger.

Practice management software like Pabau tracks each weekly consultation and flags an incomplete note before the claim goes out.

CPT Code 77336: Definition and official descriptor

CPT Code 77336 is defined by the American Medical Association, which publishes the official long descriptor for the code. The descriptor opens with “continuing medical physics consultation, including” and then names three elements:

• assessment of treatment parameters;
• quality assurance of dose delivery; and
• review of patient treatment documentation in support of the radiation oncologist.

It closes by setting the billing unit. The service is “reported per week of therapy.”

The code sits in the Medical Radiation Physics, Dosimetry, Treatment Devices and Special Services section of the CPT code set. That section covers the technical and consultative work medical physicists perform in support of radiation therapy.

All three elements have to appear in the weekly record. A note that documents only one or two of them will not support the claim on audit.

Note what the descriptor does not say. This is a patient-specific service, so routine machine quality assurance and safety-regulation testing on the linear accelerator do not belong in a 77336 note. The service is also distinct from treatment planning or simulation, and it runs as weekly oversight across the whole course of therapy.

Billing frequency and when the code applies

CPT Code 77336 is billed once per week of radiation therapy treatment. The American Society for Radiation Oncology (ASTRO) and CMS LCD L34652 both confirm this weekly cadence. A “week” is defined by the days on which treatment is delivered, not a strict calendar week from Monday to Friday.

Five conditions have to be met before a 77336 claim goes out:

• The patient must be actively receiving a course of radiation therapy during the week being billed.
• A qualified medical physicist must perform the consultation personally, not delegate it to a dosimetrist or therapy technologist.
• The physicist must assess treatment parameters, carry out quality assurance of dose delivery, and review the patient’s treatment documentation for that specific week.
• Documentation must be completed and signed by the physicist for each week separately.
• The consultation is not billable during weeks when no treatment is delivered, including treatment breaks and holidays.

Run those five checks in the same order every week, before the claim is generated.

Overbilling 77336 for weeks without active treatment is consistently flagged in OIG audit reviews of radiation oncology practices. The code is tied to weeks of treatment delivery, not to weeks within the overall care episode.

Reimbursement and fee schedule

Reimbursement for CPT Code 77336 varies by payer, by locality, and by whether the service is billed under a facility or non-facility rate.

For Medicare specifically, 77336 is reimbursed under the Medicare Physician Fee Schedule (MPFS). Rates differ depending on the place of service.

Use the CMS Physician Fee Schedule lookup tool to obtain the current locality-specific rate for your ZIP code. The national averages below are directional only, and locality adjustments vary significantly.

The Medicare Physician Fee Schedule relative value files publish the work, practice expense, and malpractice RVUs for 77336. Multiply those by the annual conversion factor and you have the benchmark most commercial contracts are negotiated against.

Modifiers for CPT Code 77336

CPT Code 77336 is a technical-component-only code. The Medicare Physician Fee Schedule assigns it PC/TC indicator 3, so it carries no professional component and no modifier 26 option.

Medicare pays it only in a setting where the technical component is separately payable. A freestanding radiation oncology center that employs its own qualified medical physicist is the standard example.

In a hospital setting, where the physicist is employed by the hospital, 77336 is a Part A cost. It is not separately billable to Part B, and no global service exists to bill.

CMS sets this out in the Billing and Coding Guidelines for Radiation Oncology (LCD L34652, Article A59350). The Medicare Claims Processing Manual, Chapter 13, Section 70.5 carries the same instruction.

That leaves a short list of modifiers worth knowing. The telehealth entries below almost never apply to a physicist’s weekly on-site consultation, but billing staff still meet them on radiation oncology claim edits.

The most common modifier error on 77336 is appending modifier 26, or splitting the code into professional and technical halves. Neither option exists for this code.

The next most common is a hospital-based provider billing Part B for physics work already covered by the hospital’s Part A payment. Check the place of service and the current NCCI edits before you submit.

Medical necessity and supporting ICD-10 codes

Medical necessity for CPT Code 77336 rests on the diagnosis that justifies the radiation therapy course. The consultation is payable only while the patient is under active treatment for that condition. Payers expect the diagnosis on the 77336 claim to match the one supporting the treatment delivery codes billed in the same week.

Most 77336 claims carry a malignant neoplasm code from the ICD-10-CM code set as the primary diagnosis. Many practices also report Z51.0 to identify the radiation therapy encounter itself. The table below shows diagnosis codes commonly paired with a course of external beam radiation therapy.

Confirm sequencing rules with each payer before submitting. Some Medicare Administrative Contractors expect the neoplasm code first, with Z51.0 in a secondary position. Reporting Z51.0 on its own, without the neoplasm that prompted treatment, is a common cause of medical necessity denials.

Documentation requirements for each billed week

Documentation is the single biggest factor in a CPT Code 77336 audit. CMS LCD L34652 and ASTRO guidance both specify what the physics consultation record must contain for each billed week.

The weekly physics consultation record must include all of the following:

• The physicist’s personal review of treatment parameters for that specific week (dose, fractionation, field arrangement)
• Quality assurance of dose delivery for that week, including a check that the dose delivered matches the approved plan
• Review of the patient’s treatment documentation in support of the radiation oncologist, covering the chart, the delivered fractions, and any imaging used to verify delivery
• Dated, personally signed entry by the qualified medical physicist (not a dosimetrist or therapist countersignature)
• Identification of the specific week of treatment being covered
• Any deviations from the original treatment plan and the corrective action taken

A brief note that says only “physics review performed” does not satisfy these requirements. The record has to show that the physicist evaluated each of the three elements named in the descriptor. On the weekly billing run, each consultation appears as its own line item with its documentation date.

Common billing errors with CPT Code 77336

Radiation oncology physics billing has been a consistent focus of OIG oversight. The six errors below account for most of the denials and takebacks that follow.

• Overbilling frequency. Billing 77336 more than once per treatment week is the most frequently cited error in OIG radiation oncology audit findings. Billing for weeks with no treatment delivered draws the same scrutiny.
• Missing physicist signature. Claims submitted without a personally signed, dated weekly note from the qualified medical physicist are denied on audit. A countersignature from a dosimetrist does not satisfy the requirement.
• Unbundling physics services. Billing 77336 alongside 77300 (basic radiation dosimetry calculation) for the same clinical activity on the same date can trigger NCCI bundling edits. Verify current CCI edits before concurrent billing.
• Incorrect modifier use. Appending modifier 26 to 77336, or billing it as a global service, denies the claim. The code is technical-only, so neither option exists. Billing Part B for a hospital-employed physicist’s work fails for the same reason.
• Billing machine quality assurance as a physics consultation. Routine linear accelerator checks and safety-regulation testing are not patient-specific services. They sit in the facility’s equipment program, and on their own they do not support a 77336 claim.
• Generic documentation. Templated notes that skip the specific week’s treatment parameters, dose delivery checks, or documentation review do not support medical necessity under LCD L34652.

Review denials on radiation oncology physics codes separately from the rest of the claim file. If 77336 denials cluster around particular weeks or payers, that pattern usually points to incomplete documentation or a modifier error. Investigate it before it escalates to a formal audit.

OIG audit risk and compliance considerations

The OIG has included radiation oncology services in its Work Plan reviews due to documented overpayment patterns in medical physics billing. ASTRO maintains a compliance resource page for members. CMS has issued coverage guidance through LCD L34652 to define the parameters of medically necessary physics consultation billing.

Key compliance safeguards for radiation oncology practices billing 77336:

• Conduct internal audits of 77336 claims quarterly, sampling at least 10-15 weekly consultation records per audit cycle.
• Compare the number of 77336 claims submitted to the number of weeks of treatment delivered. Any ratio above 1:1 per patient-week requires explanation.
• Ensure your medical billing compliance policy explicitly covers physicist consultation documentation standards.
• Train billing staff on the distinction between treatment weeks (billable) and treatment episodes (not the billing unit).

Related CPT codes to know alongside 77336

CPT Code 77336 rarely stands alone in a radiation oncology claim. Billing teams should know the codes most often billed in the same treatment episode. Use the AAPC Codify CPT lookup to verify current descriptors before concurrent billing.

The most commonly co-billed pair is 77336 and 77427. Both codes cover the same treatment course, but they represent different professional roles. 77336 is the physicist’s consultation, and 77427 is the radiation oncologist’s treatment management.

Each requires separate documentation from the professional who performed it. Check the CMS NCCI edits files for the current edit pairs before submitting concurrent claims.

How Pabau keeps weekly 77336 billing on track

Radiation oncology physics billing repeats itself. The same code and the same documentation checklist come round every week of treatment, for every patient on the machine. Track that on a spreadsheet or from memory, and a week eventually goes out with an unsigned note behind it.

Practice management software like Pabau raises the weekly prompt for you and flags an incomplete note before the claim is generated.

Claims then route through a clearinghouse that validates them against current payer edits. Pabau’s claims management software also carries CPT and ICD-10 catalogs that already include 77336 and its companion codes.

Pabau integrates with Claim.MD to submit radiation oncology claims electronically to thousands of US payers. Remittance advice comes back automatically, with the payer’s claim adjustment reason code attached to each denial. Billing staff can then fix a 77336 problem at the claim level, before the balance ages into a write-off.

Keep every weekly physics consultation billed and documented

Pabau’s claims management software tracks each weekly physics consultation, flags an incomplete note before submission, and manages denials across payers. See how it fits a radiation oncology billing workflow.

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Conclusion

The weekly rhythm is what makes 77336 easy to get wrong. One claim per treatment week is a small rule, and it only holds if someone checks the note before the claim goes out. Practices that build that check into the weekly routine rarely see a 77336 denial at all.

Treat the physicist’s signature as the trigger for billing, not as paperwork to catch up on later. Pair it with a diagnosis that matches the treatment delivery codes billed that week, and the claim is complete. Book a demo to see how Pabau tracks weekly physics consultations and the documentation behind them.

Continue your research

Need to understand how claims flow from submission to payment? Claim.MD clearinghouse overview explains how electronic claim routing works for US specialty practices.

Want to reduce denial rates across your billing team? Medical claims clearinghouse guide covers how clearinghouse validation prevents avoidable rejections before claims reach payers.

Looking for a complete picture of radiation oncology revenue cycle risks? Best medical billing software for US practices reviews the tools that handle specialty billing compliance at scale.

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