Currentblue cross blue shield - louisianaPolicy AHS - M2067 - Therapeutic Drug Monitoring for 5-Fluorouracil, 1

Therapeutic Drug Monitoring for 5-Fluorouracil

Defines coverage stance for therapeutic drug monitoring (TDM) related to 5‑fluorouracil (5‑FU) dosing adjustments for individuals receiving 5‑FU chemotherapy; affects providers requesting TDM services and laboratories performing assays.

Policy Summary

Payerblue cross blue shield - louisiana

PolicyTherapeutic Drug Monitoring for 5-Fluorouracil

Policy CodePolicy AHS - M2067 - Therapeutic Drug Monitoring for 5-Fluorouracil, 1

Change TypeNo material change

Effective Date06/01/2025

Next Review Date

Key ActionDocument that the patient is undergoing intravenous 5‑FU chemotherapy and provide plasma sampling near the end of infusion when requesting TDM to guide dose adjustment.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

AUC 20-30recommended target AUC for 5‑FU

LOQ 85 ng/mLMy5‑FU assay LOQ

Reduced grade 3/4 ADRsreported outcome with PK-guided dosing

≈62%uracil breath test sensitivity

S3722,80299,82542,83789

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Procedure codes listed

Coverage Criteria

inv-01: Covered Indication

Covered when ALL of the following are met

TDM for 5-FU: Individual is undergoing intravenous 5‑fluorouracil (5‑FU) chemotherapy and therapeutic drug monitoring (plasma sample collected near the end of infusion) is being used to aid in managing dose adjustmentAUC target commonly 20-30 mg×h×L

Assay analytical performance (eg, LOQ) should be appropriate for clinical interpretation; used to guide subsequent cycle dosing

inv-02: Not Covered Tests

Noncovered tests for dose adjustment: Uracil breath tests and dihydrouracil/uracil ratio testing of plasma, serum, or urine do not meet coverage criteria for aiding 5‑FU dose adjustment due to insufficient published evidence

These tests are explicitly listed as not meeting coverage criteria and may be denied

Uracil breath tests and dihydrouracil/uracil ratio testing of plasma, serum, or urine are excluded from coverage when proposed for the purpose of guiding 5‑fluorouracil (5‑FU) dose adjustment. These tests do not meet coverage criteria due to insufficient published evidence demonstrating they are required and beneficial for management of an individual’s 5‑FU therapy.

International and national guidance do not endorse use of the uracil breath test for clinical dosing decisions: the IATDMCT explicitly states the uracil breath test 'does not help in determining the correct dose and is not recommended for clinical use'. In addition, NICE has stated the My5‑FU assay should only be recommended for research purposes (NICE, 2014), noting promise but not recommending routine clinical adoption.

Some referenced sections and citation lists do not include additional explicit exclusions beyond those already noted for uracil breath testing and dihydrouracil/uracil ratio testing; no further exclusion statements are provided in these reference entries.

Because published evidence is insufficient to demonstrate clinical benefit for 5‑FU dose management, the use of uracil breath tests or dihydrouracil/uracil ratio testing to guide dose adjustment is considered not medically necessary and therefore does not meet coverage criteria for this indication.

Taken together, authoritative bodies emphasize caution: the IATDMCT recommends against clinical use of the uracil breath test for dose determination, while NICE limits the My5‑FU assay to research use only. These positions support excluding breath-based uracil testing and similar DHU/U ratio assays from routine coverage for 5‑FU dose adjustment.

Not all reference entries contain explicit 'not medically necessary' language; where such phrasing is absent, the policy relies on the specific exclusion language elsewhere in the document and positions from guideline organizations to define coverage determinations.

Coding and Procedure Codes

Applicable CPT/HCPCS 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.
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

Recommended target AUC for 5-FUAUC 20–30 mg×h×L

Clinical contextTarget used for intravenous continuous-infusion 5-FU to guide dose adjustments

Source study/guidance noteRecommendation cited from Mindt et al., 2019 as summarized in policy background

Provider Actions, Documentation, and Authorization

Documentation Required

TDM for 5‑FU Coverage — Provider Documentation Requirements

Therapeutic drug monitoring (TDM) of 5‑fluorouracil (5‑FU) for individuals receiving 5‑FU chemotherapy meets coverage criteria when used to guide dose adjustment. Providers should document timing of sampling (eg, plasma collected near end of IV infusion per validated protocols), indication for monitoring (dose adjustment), and results with AUC-based dose recommendations. Proprietary plasma tests intended for IV 5‑FU infusions (eg, My5‑FU) that report AUC and provide a validated dose‑adjustment algorithm are addressed under this coverage statement. Uracil breath tests and DHU/uracil ratio testing of plasma, serum, or urine do not meet coverage criteria and present a denial risk.

Document sampling timing and context (eg, near end of IV infusion) for covered TDM
Record AUC result and how dose adjustment recommendation was derived
Do not submit claims for uracil breath tests or DHU/uracil ratio testing for dose adjustment — these are not covered

Prior Authorization

Prior Authorization and Government Policy Precedence

Background and Clinical Context

5‑Fluorouracil (5‑FU) is an intravenous chemotherapeutic with a narrow therapeutic index. Therapeutic drug monitoring (TDM) based on systemic exposure measured as area-under-curve (AUC) has been proposed to optimize dosing because AUC correlates with both clinical activity and toxicity. The IATDMCT describes AUC as the 'accepted and clinically relevant' metric and reports that TDM reduces variability and toxicity and improves clinical activity in patients receiving 5‑FU, providing the rationale for AUC‑based TDM to guide dose adjustments.

Definitions

Definition — 5-FU

Term5-FU (5‑fluorouracil)

DescriptionIntravenous antimetabolite chemotherapeutic agent used alone or in combination to treat cancers such as colorectal, head and neck, gastric, breast, anal and some skin cancers.

Clinical noteAdministered commonly as continuous infusion; dosing historically by BSA but AUC-guided TDM may reduce toxicity and improve efficacy.

Definition — AUC

TermAUC (Area‑under‑curve)

DescriptionMetric of systemic drug exposure (area under the concentration–time curve) used to assess 5‑FU exposure and guide dosing.

Clinical relevance

Initial Therapy Criteria

inv-31: Initial TDM

Initial use of TDM

Initial TDM sampling: Plasma sample collected near the end of 5‑FU infusion to measure 5‑FU concentration and calculate AUC for cycle-to-cycle dose adjustmentAssay LOQ and LOD should be appropriate (example: My5‑FU LOQ 85 ng/mL)

Target AUC commonly 20–30 mg×h×L; TDM used to guide subsequent cycle dosing

inv-32: Initial dosing for DPYD variant carriers (CPIC recommendations)

CPIC recommendations at therapy initiation for DPYD genotypes

DPYD poor metabolizer initial recommendation: Avoid 5‑fluorouracil–containing regimens in DPYD poor metabolizers (activity score 0.5 or 0). If no suitable alternative exists, consider a strongly reduced starting dose with early therapeutic drug monitoring

CPIC 2017 guidance

Continuation and Titration Criteria

inv-33: Post-genotype dose titration and monitoring (CPIC guidance)

CPIC guidance on continuation/titration after initial genotype-based dosing

CPIC follow-up: For DPYD intermediate or poor metabolizers, titrate dose based on observed toxicity or therapeutic drug monitoring. For DPYD poor metabolizers for whom fluoropyrimidines are used (no alternative), start at a strongly reduced dose with early TDM and adjust upward cautiously guided by TDM and toxicity

Follow-up TDM is recommended to avoid underdosing after genotype-based reductions (CPIC 2017)

Step Therapy / Testing Sequence

Step	Action	Rationale / Notes
1	Obtain DPYD genotype (activity score) prior to initiating 5‑fluorouracil therapy	CPIC (2017) recommends DPYD genotyping to identify intermediate and poor metabolizers and guide initial dosing decisions
2	If DPYD is intermediate metabolizer: reduce starting dose based on activity score	CPIC advises dose reduction for intermediate metabolizers followed by titration based on toxicity or therapeutic drug monitoring if available
3	If DPYD is poor metabolizer (AS 0.5 or 0): avoid 5‑FU if possible; if no alternatives, give a strongly reduced starting dose with early TDM	CPIC strongly recommends avoiding 5‑FU in poor metabolizers; when used, combine strong dose reduction with early therapeutic drug monitoring
4	Perform pharmacokinetically‑guided dosing / therapeutic drug monitoring (plasma sampling near end of infusion) following any genotype-based dose reduction or when intermediate/poor metabolizer identified	CPIC recommends follow-up TDM to ensure AUC falls within targeted therapeutic range and to avoid underdosing after genotype-based reductions
5	Titrate subsequent doses based on TDM results and clinical toxicity	Pharmacokinetically‑guided dosing increases proportion of patients achieving target AUC and reduces 5‑FU related adverse effects; follow-up TDM recommended to guide titration

Site of Care and Specimen Collection

Documentation Required

Collect plasma near end of infusion; use laboratory assays

Assays for 5‑FU TDM are laboratory‑based and use plasma collected near the end of the infusion cycle; ensure specimen timing aligns with this requirement and that the assay is a laboratory assay (eg, My5‑FU described as plasma near end of infusion).

Collect plasma sample near the end of the 5‑FU infusion for measurement
Use laboratory‑based assays to quantify 5‑FU (eg, My5‑FU)

Auxiliary Coding Notes

Billing Rule

Reference procedure codes

Procedure/CPT/HCPCS codes listed in the policy for convenience and billing reference: S3722, 80299, 82542, 83789.

S3722
80299
82542
83789

Revision History

2025-06-01Effective dateLatest

Policy effective date updated to 2025-06-01

Policy Summary

Payerblue cross blue shield - louisiana

PolicyTherapeutic Drug Monitoring for 5-Fluorouracil

Policy CodePolicy AHS - M2067 - Therapeutic Drug Monitoring for 5-Fluorouracil, 1

Change TypeNo material change

Effective Date06/01/2025

Next Review Date

Key ActionDocument that the patient is undergoing intravenous 5‑FU chemotherapy and provide plasma sampling near the end of infusion when requesting TDM to guide dose adjustment.

SourceLink

On This Page

Providers should follow any applicable prior authorization requirements defined by the member's benefit plan or payer system. This policy does not specify a universal prior authorization requirement; check member-specific benefit plan rules. If government (Medicare/Medicaid) policies apply and differ from this policy, the government policy takes precedence.

Verify prior authorization requirements in the member's benefit plan before performing TDM
When Medicare/Medicaid LCDs or NCDs apply, those determinations override this policy

Note

No Explicit Authorization/Denial Triggers Specified

No specific authorization or denial triggers (eg, laboratory thresholds or automatic denial rules) are defined within this policy. Coverage determinations should be based on documented medical necessity, sampling and test methodology, and applicable benefit rules or government policies.

Absence of explicit triggers means reviewer will evaluate documentation and clinical context
Ensure medical record supports use of TDM for dose optimization

Documentation Required

Genotype-Guided Dosing Followed by TDM (CPIC Recommendation)

When genotype-guided dosing (DPYD testing) is used to inform initial 5‑FU dosing, follow-up pharmacokinetically-guided TDM is recommended per CPIC guidance to titrate dose and avoid under- or overdosing. Document DPYD activity score, initial dose adjustments based on genotype, and subsequent TDM results and dose titration decisions.

DPYD poor metabolizers: avoid 5‑FU when possible; if used, consider strongly reduced starting dose with early TDM
DPYD intermediate metabolizers: reduce starting dose per activity score, then titrate using toxicity assessment or TDM
Document genotype-based recommendations and subsequent TDM-based titration

Billing Rule

Procedure Codes / Billing Reference

Billing codes commonly used for 5‑FU AUC/TDM and associated laboratory methods are listed for provider reference. Use payer-specific billing guidance and ensure documentation supports the billed code.

S3722 — Dose optimization by AUC analysis for infusional 5‑fluorouracil
80299 — Quantitation of therapeutic drug, not elsewhere specified
82542 — Column chromatography (includes MS methods) for non-drug analytes
83789 — Mass spectrometry and tandem mass spectrometry for non-drug analytes

Documentation Required

Laboratory Validation and CLIA Requirements

Laboratory-developed tests (LDTs) used for TDM must be validated and performed in CLIA-certified high-complexity laboratories. FDA clearance is not required for LDTs, but documentation of the laboratory method and validation should be available upon request.

Ensure the performing lab is CLIA-certified and maintains validation records for the assay
Include assay method and limits of detection/quantitation in patient record or test report when available

IATDMCT endorses AUC as an accepted and clinically relevant metric correlating with 5‑FU activity and toxicity.

Definition — TDM

TermTDM (Therapeutic Drug Monitoring)

DescriptionClinical practice of measuring drug concentrations at designated intervals to maintain target systemic levels and optimize individual dosing regimens.

Application to 5‑FUUsed to measure plasma 5‑FU near end of infusion to calculate AUC and guide subsequent dose adjustments to reduce toxicity and improve efficacy.

Definition — DPD/DPYD

TermDPD / DPYD (dihydropyrimidine dehydrogenase)

DescriptionEnzyme encoded by DPYD gene responsible for catabolism of fluoropyrimidines; deficiency increases risk of severe 5‑FU toxicity.

Clinical implicationDPYD genotyping (activity score) informs starting dose adjustments and may prompt early TDM per CPIC guidance.

Definition — AUC (alternate chunk)

TermAUC (alternate description)

DescriptionArea-under-curve; accepted metric for assessing systemic exposure to 5‑FU with established correlations to clinical activity and toxicity.

Guideline noteIATDMCT and other bodies reference AUC when recommending TDM for 5‑FU dosing management.

Definition — DPYD genotype/Activity Score

TermDPYD genotype / Activity Score (AS)

DescriptionDPYD activity score classifies metabolizer status (e.g., intermediate or poor) to guide fluoropyrimidine dosing decisions.

CPIC guidanceFor DPYD intermediate metabolizers reduce starting dose and titrate by toxicity or TDM; for poor metabolizers avoid 5‑FU or use strongly reduced dose with early TDM if no alternatives.

Definition — My5‑FU assay / 5‑FU TDM

AssayMy5‑FU assay (5‑FU therapeutic drug monitoring)

DescriptionProprietary plasma assay intended to guide 5‑FU dose adjustment by measuring 5‑FU concentrations (performed on plasma collected near end of infusion).

Regulatory/guidance noteNICE (2014) recommended the My5‑FU assay only for research purposes; laboratories performing LDTs must validate assays under CLIA.

DPYD intermediate metabolizer initial recommendation: Reduce starting dose based on DPYD activity score for intermediate metabolizers and consider early therapeutic drug monitoring as clinically indicated

CPIC 2017 guidance