CurrentOscar HealthPolicy N/A

Therapeutic Drug Monitoring for 5-Fluorouracil

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Defines Oscar Health's coverage stance and clinical background for therapeutic drug monitoring (TDM) of intravenous 5-FU, including which TDM methods meet criteria and which do not, for providers submitting authorizations and claims.

Policy Summary

PayerOscar Health

PolicyTherapeutic Drug Monitoring for 5-Fluorouracil

Policy CodePolicy N/A

Change TypeNo material change

Effective DateOct 1, 2026

Last ReviewJun 16, 2026

Next Review DateJun 16, 2026

Key ActionSubmit documentation for therapeutic drug monitoring of IV 5-FU when requesting authorization and code services accurately to avoid denial.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

TDMMeets criteria

Uracil testsDoes not meet

20–30AUC target

MultipleRCT/meta-analysis

06/16/2026

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CurrentOscar HealthPolicy N/A

Therapeutic Drug Monitoring for 5-Fluorouracil

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Policy Summary

PayerOscar Health

PolicyTherapeutic Drug Monitoring for 5-Fluorouracil

Policy CodePolicy N/A

Change TypeNo material change

Effective DateOct 1, 2026

Last ReviewJun 16, 2026

Next Review DateJun 16, 2026

Key ActionSubmit documentation for therapeutic drug monitoring of IV 5-FU when requesting authorization and code services accurately to avoid denial.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

TDMMeets criteria

Uracil testsDoes not meet

20–30AUC target

MultipleRCT/meta-analysis

06/16/2026

Coverage Criteria — When 5‑FU TDM Meets Criteria

Indications That Meet Criteria

Covered when ALL of the following are met

TDM for 5-FU chemotherapy: Therapeutic drug monitoring to aid dose adjustment for individuals undergoing 5-fluorouracil (5-FU) chemotherapy.

Applies to individuals receiving intravenous 5-FU infusion; target AUC guidance provided elsewhere in the policy.

Tests That Do Not Meet Criteria

Not covered when the test is the following

Non-covered TDM methods: Uracil breath tests.

Listed explicitly as not meeting criteria due to insufficient published scientific literature.

Non-covered TDM methods: Dihydrouracil/uracil ratio testing of plasma, serum, or urine samples.

Listed explicitly as not meeting criteria due to insufficient published scientific literature.

Uracil breath tests and dihydrouracil/uracil ratio testing of plasma, serum, or urine are explicitly listed as methods that do not meet criteria for aiding dose adjustment of 5‑fluorouracil (5‑FU) chemotherapy due to insufficient published evidence supporting their clinical benefit.

Regulatory guidance from the European Medicines Agency (EMA) pharmacovigilance committee (PRAC) concludes that systemic 5‑FU and related substances are contraindicated in patients with known complete DPD (DPYD) deficiency; PRAC also recommends DPD deficiency testing prior to treatment and dose adjustment for partial deficiency.

Within the cited reference sections of this document there are no additional explicit coverage exclusions beyond the tests and contraindications already described in the policy; the evidence sections list bibliographic references rather than new exclusion statements.

Use of uracil breath tests or dihydrouracil/uracil ratio testing to guide 5‑FU dosing is considered not meeting criteria (not medically necessary) because the policy states these specific methods lack sufficient published scientific literature to demonstrate they are required and beneficial for patient management.

The National Institute for Health and Care Excellence (NICE) has stated that the proprietary My5‑FU assay shows promise but should be used only for research purposes and is not recommended for routine clinical use.

No explicit additional statements labeling tests as 'not medically necessary' are present in the referenced evidence sections; those sections are bibliographic citations supporting the policy rather than standalone coverage determinations.

Coding — Procedure & Laboratory Codes

Applicable coding guidancemixed

No codes listed

Applicable procedure codesCPT | HCPCS

S3722	Dose optimization by area under the curve (AUC) analysis, for infusional 5‑fluorouracil.
80299	Quantitation of therapeutic drug, not elsewhere specified.
82542	Column chromatography, includes mass spectrometry, if performed (eg, HPLC, LC, LC/MS, LC/MS‑MS, GC, GC/MS‑MS, GC/MS, HPLC/MS), non‑drug analyte(s) not elsewhere specified, qualitative or quantitative, each specimen.

Laboratory analysis codesCPT

83789

Mass spectrometry and tandem mass spectrometry (eg, MS, MS/MS, MALDI, MS‑TOF, QTOF), non‑drug analyte(s) not elsewhere specified, qualitative or quantitative, each specimen.

5-FU target AUC — numeric target range

5-FU target AUC20–30 mg·h/L

Unitmg·h·L⁻¹ (reported as mg·h/L)

PurposeTarget AUC range used to guide dose‑optimization for intravenous 5‑FU infusion

Uracilemia thresholds and associated guidance

Uracilemia threshold — highU > 16 ng/mL — associated with recommendations to decrease 5‑FU dose

Uracilemia threshold — lowU < 16 ng/mL — associated with higher 5‑FU exposure in Dolat et al. and may benefit from dose increase with TDM

Provider Actions — Authorization, Documentation, and Billing

Prior Authorization

Prior authorization / coverage stance for 5‑FU TDM

Therapeutic drug monitoring (TDM) to aid dose adjustment for individuals undergoing intravenous 5‑fluorouracil chemotherapy meets the policy's coverage criteria; conversely, uracil breath tests and dihydrouracil/uracil ratio testing do not meet criteria and are excluded.

Meets criteria: TDM for individuals receiving 5‑FU infusion to manage dose adjustment.
Does not meet criteria: Uracil breath tests and dihydrouracil/uracil ratio testing of plasma, serum, or urine.

Billing Rule

Procedure codes to use for prior authorization and claims

List the applicable procedure codes when requesting authorization or submitting claims for 5‑FU TDM: S3722, 80299, 82542, and 83789 are provided by the policy as the relevant CPT/HCPCS procedure codes for AUC dose‑optimization and associated laboratory quantitation.

Initial Therapy — Genotype and TDM Integration

Genotype‑guided initial dosing and TDM

DPYD genotype-guided dosing with follow-up: For individuals with DPYD variants, use genotype-guided starting dose modifications and follow with therapeutic drug monitoring (TDM) if available to titrate dosing.

Per CPIC: for DPYD intermediate metabolizers reduce starting dose based on activity score and titrate by toxicity or TDM; for DPYD poor metabolizers avoid 5-FU if possible, but if no alternatives, use a strongly reduced starting dose with early TDM.

Site of Care — Where TDM Is Performed

Note

Site‑of‑care action: collect plasma near end of 5‑FU infusion for TDM assays

TDM described in this policy applies to patients receiving 5‑FU via intravenous infusion; plasma sampling is performed near the end of the infusion cycle for assays used to calculate AUC and guide dosing.

Intended for patients receiving 5‑FU through intravenous infusion; plasma taken near end of infusion for assay.
My5‑FU and similar proprietary tests use plasma AUC calculations to guide subsequent dosing.

Documentation Required

Arrange sample collection and lab processing with CLIA‑certified high‑complexity labs

TDM assays are typically performed by CLIA‑certified high‑complexity laboratories; sample collection may occur in outpatient infusion centers, hospital outpatient departments, or offices according to lab workflow and clinical needs.

LDTs are regulated under CLIA as high‑complexity tests and are performed in‑house by qualified labs.

Definitions & Abbreviations

Definition: 5-FU

Abbreviation5-FU = 5‑fluorouracil

FormulationTypically administered as continuous intravenous infusion

Therapeutic roleAntimetabolite chemotherapeutic agent used in multiple solid tumors (eg, colorectal, head and neck, breast)

Definition: AUC

AbbreviationAUC = Area‑under‑curve

RoleAccepted metric for assessing systemic 5‑FU exposure and used to guide AUC‑based dosing (target 20–30 mg·h/L)

Measurement

Background — Clinical Rationale for 5‑FU TDM

5‑Fluorouracil (5‑FU) is an intravenously infused chemotherapeutic agent with a narrow therapeutic index. Although body surface area (BSA) dosing is common, the policy recognizes therapeutic drug monitoring (TDM) using AUC‑targeted dosing — with an accepted target range of 20–30 mg·h/L — as a clinically relevant approach to individualize dosing and reduce toxicity for patients receiving IV 5‑FU.

Revision History & Governance

2026-10-01effective_dateLatest

Policy became effective for therapeutic drug monitoring of intravenous 5‑fluorouracil (5‑FU).

2026-06-16last_review

Clinical evidence, coding, and references were reviewed and documented (last review date recorded).

Policy Summary

PayerOscar Health

PolicyTherapeutic Drug Monitoring for 5-Fluorouracil

Policy CodePolicy N/A

Change TypeNo material change

Effective DateOct 1, 2026

Last ReviewJun 16, 2026

Next Review DateJun 16, 2026

Key ActionSubmit documentation for therapeutic drug monitoring of IV 5-FU when requesting authorization and code services accurately to avoid denial.

SourceLink

On This Page

Clinical implicationPatients with U > 16 ng/mL may be at risk of under‑exposure if dose reductions are applied without TDM; TDM recommended to avoid loss of efficacy

S3722 — Dose optimization by AUC analysis, for infusional 5‑fluorouracil.
80299 — Quantitation of therapeutic drug, not elsewhere specified.
82542 — Column chromatography (eg, HPLC, LC/MS, LC/MS‑MS), each specimen.
83789 — Mass spectrometry/tandem mass spectrometry, each specimen.

Note

No separate prior‑authorization procedure detailed in this section

The policy text includes no separate, explicit prior authorization program requirements in these sections; it provides coverage determinations and coding guidance but does not specify unique prior authorization steps beyond standard payer rules.

No additional prior‑authorization-specific instructions are stated in the Indications/Limitations sections.
Follow standard Oscar prior authorization processes if applicable per member benefit and payer rules.

Step Therapy

Follow CPIC genotype‑guided dosing with follow‑up TDM

CPIC recommends genotype‑guided starting dose reductions for DPYD variant carriers and advises follow‑up therapeutic drug monitoring (if available) to titrate dosing, which should be followed in clinical management.

For DPYD intermediate metabolizers: reduce starting dose based on activity score and follow with toxicity‑based titration or TDM if available.
For DPYD poor metabolizers: avoid 5‑FU where possible; if used, administer a strongly reduced starting dose with early TDM.

Documentation Required

Required documentation and coding accuracy

Providers must submit accurate documentation of services performed and code claims according to industry standard coding guidelines; failure to follow coding/billing guidance may result in claim denial or recoupment.

Document the procedure performed, test method, and clinical indication in the medical record.
Code claims per CPT/HCPCS, ICD‑10, NDC, and other applicable coding manuals and payer rules.

Documentation Required

Documentation expectation for LDTs and CLIA validation

Clinical laboratories performing 5‑FU TDM commonly use laboratory‑developed tests (LDTs) that must be validated and performed in‑house under CLIA high‑complexity rules; documentation of CLIA validation and test method may be expected by the payer.

LDTs are regulated under CLIA '88 as high‑complexity tests and are not FDA‑cleared/approved.
Be prepared to provide evidence of laboratory validation and CLIA certification if requested.

Denial Risk

Denial risk: coding and documentation noncompliance

Claims may be denied or recouped if coding/billing guidelines or current reimbursement policies are not followed; ensure adherence to billing rules and accurate submission.

Follow Uniform Billing Editor, AMA CPT guidance, HCPCS, ICD‑10, and CMS coding manuals.
Noncompliance with coding/billing guidance can lead to denial or payment recoupment.

Denial Risk

Coverage determinations must defer to applicable governmental policies

When there is a conflict between this policy and any applicable governmental policy (e.g., LCDs, NCDs, or state Medicaid rules), coverage determinations must defer to the governmental policy; failure to follow applicable government policy may affect coverage.

Check relevant Medicare (LCD/NCD) and state Medicaid policies for the member before authorization or billing.
Government policy supersedes this payer policy where conflicts exist.

Note

No additional explicit authorization or denial criteria in evidence section

This section contains only evidence references and does not provide additional explicit authorization or denial criteria beyond the coverage determinations already stated (TDM meets criteria; specified uracil‑based tests do not).

No separate authorization/denial decision rules are defined in the Evidence References section.
Use the Indications/Limitations (III) and coding sections for operational authorization decisions.

Sample collection for these assays commonly occurs in infusion centers or other outpatient settings.

Calculated from plasma concentration vs time curve

Definition: TDM

AbbreviationTDM = Therapeutic drug monitoring

PurposeMeasuring drug concentrations at designated intervals to maintain target plasma exposure and optimize individual dosage regimens

Clinical effectFor 5‑FU, TDM has reduced toxicity and improved efficacy in trials and is recommended by IATDMCT for certain regimens

Definition: DPD/DPYD

AbbreviationDPD/DPYD = Dihydropyrimidine dehydrogenase

Clinical relevanceDPD/DPYD activity affects 5‑FU clearance and toxicity risk; genotype and phenotype assessments inform dosing

Contraindication noteComplete DPD deficiency is listed as a contraindication to systemic 5‑FU by EMA/PRAC

Area‑under‑the‑curve (AUC)

DefinitionArea‑under‑the‑curve (AUC) — accepted and clinically relevant metric for assessing systemic 5‑FU exposure and its relation to activity and toxicity.

EvidenceIATDMCT notes significant correlations between 5‑FU exposure (AUC) and clinical activity/toxicity across disease types and dosing regimens

Use in dosingAUC used to target 20–30 mg·h/L for infusion 5‑FU dose optimization

Definition: Laboratory‑developed test (LDT)

DefinitionLaboratory‑developed test (LDT) — in‑house assays validated under CLIA high‑complexity rules; not FDA cleared/approved for clinical use.

RegulationLDTs are regulated by CMS under CLIA '88 as high‑complexity tests

Clinical noteMany clinical labs use LDTs for 5‑FU TDM and must validate methods in‑house

DPD deficiency / uracil‑based phenotyping

DefinitionDPD deficiency / uracil‑based phenotyping — screening for DPD activity using plasma uracil (uracilemia) is referenced as relevant to reducing severe 5‑FU toxicity.

Clinical findingsDolat et al. found patients with U < 16 ng/mL had higher 5‑FU exposure and benefited from dose increases guided by TDM; U > 16 ng/mL is linked to dose‑reduction recommendations

LimitationsUracil breath tests and dihydrouracil/uracil ratio testing are explicitly listed as not meeting criteria for guiding 5‑FU dose adjustment

5‑FU therapeutic drug monitoring (TDM)

Definition5‑FU therapeutic drug monitoring — measuring plasma exposure of 5‑fluorouracil to guide dose adjustment.

Clinical effectTDM for 5‑FU has been shown to reduce toxicity and improve efficacy compared with BSA dosing in multiple studies

Recommended useIATDMCT strongly recommends TDM to manage 5‑FU therapy in colorectal and head‑and‑neck cancer regimens