CurrentViva HealthPolicy IC-0362

Crysvita (burosumab-twza) (Subcutaneous) — Coverage Criteria

Medical policy governing prior authorization, coverage criteria, dosing, and renewal for Crysvita (burosumab-twza) for X-linked hypophosphatemia (XLH) and tumor-induced osteomalacia (TIO) for Viva Health members.

Policy Summary

PayerViva Health

PolicyCrysvita (burosumab-twza) (Subcutaneous) — Coverage Criteria

Policy CodePolicy IC-0362

Change TypeNo material changes

Effective Date

Next Review Date

Key ActionObtain prior authorization (initial valid 6 months; renewals every 12 months) and document baseline fasting serum phosphorus, TmP/GFR, GFR, diagnosis confirmation, and specialist involvement.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

6 moinitial prior authorization duration

12 morenewal prior authorization duration

J0584HCPCS code

90/14dXLH max units

180/14dTIO max units

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Coverage and Eligibility Criteria

Initial Approval Criteria

Covered when ALL of the following are met

Universal criteria: Must be prescribed by, or in consultation with, a nephrologist or endocrinologist; Will not be used concomitantly with oral phosphate and/or active vitamin D analogs; Patient does not have severe renal impairment (GFR <30 mL/min); Patient 25-hydroxy vitamin D levels will be monitored at baseline and intermittently and patient will be supplemented with cholecalciferol or ergocalciferol to maintain levels in the normal range for age

Baseline laboratory and diagnostic criteria: Patient has not received oral phosphate and/or active vitamin D analogs within 1 week prior to the start of therapy; Baseline fasting serum phosphorus level with current hypophosphatemia (phosphate below the lower limit of the laboratory normal reference range); Reduced tubular resorption of phosphate corrected for GFR (TmP/GFR); Other causes of hypophosphatemia have been ruled out; Note: phosphorus and other labs (GFR, TmP/GFR) should be obtained fasting ≥12 hours and within 28 days of administration

Indication-specific criteria: For XLH: patient is at least 6 months of age AND diagnosis confirmed by either FGF23 >30 pg/mL (>230 RU/mL in children 3 months-17 years; >180 RU/mL in adults using EDTA plasma) OR PHEX gene mutation; adults must have had an inadequate response to oral phosphate and active vitamin D analogs. For TIO: patient is at least 2 years of age AND diagnosis of TIO associated with phosphaturic mesenchymal tumors that cannot be curatively resected or localized AND diagnosis confirmed by excessive serum FGF23 (≥100 pg/mL) not amenable to cure by surgical excision

Renewal Criteria

Renewal covered when ALL of the following are met

Continued eligibility: Patient continues to meet the universal and indication-specific relevant criteria from initial approval; Absence of unacceptable toxicity (examples include severe hypersensitivity reactions, hyperphosphatemia and/or nephrocalcinosis, severe injection site reactions); Current serum phosphorus level is not above the upper limit of the laboratory normal reference range; Evidence of disease response (increased serum phosphorus, improvement in renal phosphate wasting, reduction in serum total alkaline phosphatase activity, symptomatic or radiographic improvement)

Pediatric XLH patients should be re-evaluated at adulthood to determine if continued therapy is necessary

Interruption criteria for tumor treatment: If patient undergoes treatment of the underlying tumor (surgical excision or radiation therapy), therapy should be interrupted and serum phosphorus reassessed after treatment completion to determine need for continued therapy

Burosumab will not be used concomitantly with oral phosphate and/or active vitamin D analogs. Prescribing must be by or in consultation with a nephrologist or endocrinologist. Do not initiate in patients with severe renal impairment (GFR <30 mL/min). Baseline and intermittent monitoring of 25-hydroxy vitamin D is required and patients should be supplemented with cholecalciferol or ergocalciferol as needed to maintain age-appropriate normal levels.

The policy statements above apply to non‑Medicare coverage determinations. For Medicare Part B drug coverage, providers must follow the Medicare Benefit Policy Manual (Pub. 100-2), Chapter 15, §50 and comply with any applicable National Coverage Determinations (NCDs), Local Coverage Determinations (LCDs), or Local Coverage Articles (LCAs). The CMS Coverage Database should be consulted for relevant NCD/LCD/LCA documents.

Therapy is considered not medically necessary when current serum phosphorus is documented to be at or above the laboratory upper limit of normal. Renewal will be denied if there is evidence of unacceptable toxicity (examples include severe hypersensitivity, hyperphosphatemia, nephrocalcinosis, or severe injection-site reactions) or if clinical and laboratory response criteria are not met.

Billing Codes, Diagnosis Codes, and Lab Thresholds

Covered HCPCS CodesHCPCSCovered

J0584

Injection, burosumab-twza 1 mg

Product NDCsNDC

42747-0102-xx	Crysvita 10 mg/mL single-dose vial
42747-0203-xx	Crysvita 20 mg/mL single-dose vial
42747-0304-xx	Crysvita 30 mg/mL single-dose vial

Covered Diagnosis CodesICD-10Covered

E83.31	Familial hypophosphatemia
E83.39	Other disorders of phosphorus metabolism
M83.8	Other adult osteomalacia

Medicare Part B Covered Diagnosis CodesICD-10

N/A	Medicare Part B Covered Diagnosis Codes (applicable to existing NCD/LCD): N/A

FGF23 thresholds — numeric thresholds used to confirm XLH or TIO diagnoses

XLH FGF23 thresholdSerum FGF23 >30 pg/mL (also specified as >230 RU/mL in children 3 months–17 years; >180 RU/mL in adults using EDTA plasma)

TIO FGF23 thresholdExcessive serum FGF23 i.e., level ≥100 pg/mL for tumor‑induced osteomalacia

Use of genetic testing for XLHPHEX gene mutation identification can confirm XLH diagnosis as an alternative to elevated FGF23

Timing for baseline labs — required timing (within 28 days) and fasting instructions for labs

Required timing for baseline labsBaseline labs (GFR, serum phosphorus, TmP/GFR) must be obtained within 28 days of planned administration

Prior Authorization, Documentation, and Billing Guidance

Prior Authorization

Prior Authorization Required

Prior authorization is required for initiation and continuation of therapy. Initial prior authorization will be valid for 6 months. Renewals may be requested and, if approved, will be issued for up to 12 months.

Initial authorization length: 6 months
Renewal authorization length: up to 12 months
Operational note: Submit prior authorization requests with complete clinical documentation as listed below to avoid delays

Note

Medicare Part B Coverage Reference

For Medicare beneficiaries, providers must follow Medicare Part B coverage rules as specified in the Medicare Benefit Policy Manual (Pub. 100-02), Chapter 15, §50 Drugs and Biologicals, and comply with any applicable NCDs, LCDs, or LCAs.

Consult applicable NCDs/LCDs/LCAs when billing Medicare Part B
Medicare Part B covered diagnosis codes: N/A (per source)

Background and Clinical Context

Burosumab is a monoclonal antibody that binds and inhibits fibroblast growth factor 23 (FGF23), reducing renal phosphate wasting and increasing serum phosphate. It is indicated for treatment of X-linked hypophosphatemia (XLH) and tumor-induced osteomalacia (TIO), with diagnostic confirmation for XLH typically by elevated FGF23 or PHEX mutation and for TIO by excessive FGF23 and nonresectable or nonlocalizable phosphaturic tumors. Baseline and ongoing monitoring of fasting serum phosphorus and related renal phosphate measures is required to guide dosing and assess response.

Definitions and Diagnostic Confirmation

XLH diagnosis confirmation — diagnostic criteria and PHEX mutation mention

Key XLH diagnostic criterion (FGF23)Serum FGF23 >30 pg/mL (or >230 RU/mL in children 3 months–17 years; >180 RU/mL in adults using EDTA plasma)

Genetic confirmationIdentification of a PHEX gene mutation in the patient confirms XLH diagnosis as an alternative to FGF23 elevation

Age requirementPatient must be at least 6 months of age to meet XLH indication criteria

Adult step requirementAdult patients must have had an inadequate response to oral phosphate and active vitamin D analogs

TIO diagnosis confirmation — criteria when tumor cannot be resected/localized

TIO diagnostic age criterionPatient must be at least 2 years of age for TIO indication

Policy Summary

PayerViva Health

PolicyCrysvita (burosumab-twza) (Subcutaneous) — Coverage Criteria

Policy CodePolicy IC-0362

Change TypeNo material changes

Effective Date

Next Review Date

SourceLink

On This Page

Fasting instruction for phosphorusPhosphorus levels should be obtained after fasting ≥12 hours (no food or drink except water)

Washout prior to baseline labsObtain labs after an adequate washout period from phosphate or active vitamin D supplements (no such agents within 1 week prior to start)

None listed — placeholder (no additional thresholds provided)

Inventory noteNone listed in the thresholds section; no additional numeric thresholds specified in appendix

Medicare applicabilityMedicare-specific coverage rules (NCDs/LCDs/LCAs) may still apply and are not replaced by these non‑Medicare thresholds

Documentation fallbackIf additional thresholds are needed, consult the Medicare Coverage Database or full policy document for details

Step Therapy

Step Therapy — Adult XLH

Step therapy requirement for adult XLH: coverage for adults with X-linked hypophosphatemia requires documentation that the patient had an inadequate response to prior treatment with oral phosphate and active vitamin D analogs.

Applicable population: adults with XLH
Required documentation: prior trials of oral phosphate and active vitamin D analogs with inadequate response

Note

Reference — CMS Coverage Database

Providers should consult the CMS Medicare Coverage Database for current NCDs, LCDs, and LCAs that may affect coverage or billing for Medicare patients.

CMS Coverage Database: https://www.cms.gov/medicare-coveragedatabase/search.aspx
Check for relevant NCDs/LCDs/LCAs prior to submitting Medicare claims

Denial Risk

Triggers for Potential Denial

Prior authorization and coverage may be denied when essential clinical documentation or required diagnostic findings are missing or when alternative causes have not been excluded.

Lack of documented fasting hypophosphatemia (fasting serum phosphate below lab reference range)
Absence of reduced TmP/GFR consistent with renal phosphate wasting
Failure to rule out other causes of hypophosphatemia (e.g., other genetic hypophosphatemic rickets)
No documentation of inadequate response to oral phosphate and active vitamin D analogs in adults with XLH

Billing Rule

Medicare Policy Compliance

Noncompliance with applicable Medicare NCDs, LCDs, or LCAs may affect coverage determinations and payment for Medicare beneficiaries. When treating Medicare patients, ensure documentation and requests conform to both this policy and any controlling Medicare policies.

Noncompliance with Medicare coverage policies may result in claim denials or recoupment
When conflicts exist, follow Medicare NCD/LCD/LCA requirements for Medicare patients

Documentation Required

Required Clinical and Diagnostic Documentation

Required clinical and diagnostic documentation must be submitted with the prior authorization request: baseline fasting serum phosphorus (obtained after a ≥12-hour fast and washout from supplements), TmP/GFR demonstrating reduced tubular phosphate reabsorption, GFR (to confirm GFR ≥30 mL/min), relevant FGF23 or genetic testing when applicable, and timing of labs within 28 days of planned administration.

Baseline fasting serum phosphorus (fasting ≥12 hours) within 28 days of administration
TmP/GFR consistent with reduced tubular phosphate reabsorption within 28 days
GFR to document renal function (GFR ≥30 mL/min required) within 28 days
FGF23 level or PHEX mutation testing when indicated for XLH or TIO diagnosis
Documentation that other causes of hypophosphatemia have been ruled out

Note

Additional Guidance (Reserved)

(Reserved) See CMS appendix and policy-specific criteria above for additional guidance relevant to Medicare and non‑Medicare populations.

Tumor status requirementTIO must be associated with phosphaturic mesenchymal tumors that cannot be curatively resected or localized

FGF23 confirmation for TIODiagnosis confirmed by excessive serum FGF23 (level ≥100 pg/mL) when tumor is not amenable to surgical cure

Interruption noteIf tumor is subsequently treated (surgery/radiation), therapy should be interrupted and serum phosphorus reassessed

CMS coverage documents — abbreviations and relevance

NCDNational Coverage Determination — an official CMS policy that applies nationally and may govern Medicare coverage for a drug or service

LCDLocal Coverage Determination — jurisdiction‑level Medicare coverage guidance issued by a Medicare Administrative Contractor (MAC)

LCALocal Coverage Article — supplemental guidance for claims processing or benefit clarification related to LCDs or billing under Part B