Home › Drugs › Kadcyla (J9354)

Kadcyla (ado-trastuzumab emtansine, T-DM1) — HCPCS J9354

Genentech (Roche) · 100 mg + 160 mg single-dose lyophilized vials · IV infusion (90 min cycle 1, 30 min cycles 2+) · HER2-targeted ADC for metastatic + adjuvant HER2+ breast cancer

Kadcyla is the original HER2-directed antibody-drug conjugate (ADC), billed under HCPCS J9354 at 1 mg per unit. Weight-based dosing: 3.6 mg/kg IV q3w — same dose for metastatic HER2+ breast cancer and for the KATHERINE adjuvant indication (early-stage HER2+ with residual invasive disease post-neoadjuvant taxane + trastuzumab, 14-cycle course). Distinct from Enhertu (J9358, T-DXd) — different payload (DM1 maytansinoid vs deruxtecan), different dose, different eligibility tier. HER2 IHC 3+ or 2+/ISH+ required. JW common — pick a 100 mg + 160 mg vial combination to minimize waste. Q2 2026 Medicare reimbursement: $42.198/mg ($10,971.48 per 260 mg billed dose for a 70 kg patient, ASP + 6%). THREE BOXED WARNINGS: hepatotoxicity (rare fatal hepatic failure), left ventricular dysfunction (LVEF assessment q3 mo), and embryo-fetal toxicity.

✓ASP data:Q2 2026 (live)
✓Payer policies:verified May 2026
✓Manufacturer guide:Genentech Access Solutions 2026
✓FDA label:most recent revision (KATHERINE indication May 2019)
✓Page reviewed:
Boxed WarningsThree FDA boxed warnings — high-acuity safety monitoring required.

1. Hepatotoxicity

Serious hepatobiliary disorders, including fatal hepatic failure, have been reported. Monitor liver function (AST, ALT, total bilirubin, alkaline phosphatase) before initiation, before each dose, and as clinically indicated. Reduce dose, hold, or permanently discontinue per FDA label thresholds for transaminase or bilirubin elevations. Nodular regenerative hyperplasia of the liver has also been reported.

2. Left ventricular dysfunction

Kadcyla can cause LV dysfunction. Assess LVEF before initiation of Kadcyla and every 3 months during treatment. Withhold or permanently discontinue per LVEF criteria in the FDA label.

3. Embryo-fetal toxicity

Kadcyla can cause fetal harm. Verify pregnancy status before initiation in patients of reproductive potential. Counsel on effective contraception during therapy and for at least 7 months after the last dose.

Instant Answer — the 5 things you need to bill J9354

HCPCS
J9354
1 mg = 1 unit
Standard dose
3.6 mg/kg
IV q3w (both mBC + adjuvant)
Modifier
JW
Often present (weight-based + 100/160 mg vials)
Admin CPT
96413+96415
Cycle 1 (90 min); 96413 only cycles 2+
Medicare ASP+6%
$42.198
per mg, Q2 2026 · $10,971.48/260 mg
HCPCS descriptor
J9354 — "Inj, ado-trastuzumab emt 1mg" Permanent
Dosing — mBC
3.6 mg/kg IV q3w — HER2+ metastatic breast cancer, prior trastuzumab + taxane (separately or in combination)
Dosing — KATHERINE adjuvant
3.6 mg/kg IV q3w × 14 cycles total — HER2+ early-stage breast cancer with residual invasive disease after neoadjuvant taxane + trastuzumab
NDCs
50242-088-01 (100 mg) and 50242-087-01 (160 mg) — single-dose vials
Vials
100 mg + 160 mg single-dose lyophilized vials — combine to minimize waste. Reconstitute 100 mg with 5 mL / 160 mg with 8 mL Sterile Water for Injection → 20 mg/mL.
Route
IV infusion. Cycle 1 over 90 minutes (in-line filter required, 0.20- or 0.22-micron). Cycles 2+ over 30 minutes if cycle 1 well tolerated.
Biomarker
HER2 IHC 3+ or IHC 2+ with ISH-positive required. HER2-low / HER2-ultralow patients are NOT eligible (use Enhertu).
Boxed warnings
Three — hepatotoxicity, left ventricular dysfunction, embryo-fetal toxicity
FDA approval
Initial approval February 22, 2013 (mBC post-Herceptin, BLA 125427). Expanded May 3, 2019 for early-stage HER2+ residual disease post-neoadjuvant (KATHERINE).
Calculate patient estimate → Read full reference Download 1-page PDF
⚠️
Kadcyla (T-DM1, J9354) is NOT Enhertu (T-DXd, J9358) — they are two different HER2 ADCs. Same target (HER2), different payload (DM1 maytansinoid vs deruxtecan topoisomerase-I inhibitor), different dose (3.6 vs 5.4 mg/kg q3w), different eligibility (HER2+ only for Kadcyla; HER2+, HER2-low, HER2-ultralow, HER2-mutant NSCLC, and tumor-agnostic for Enhertu). They are not interchangeable on the claim — using the wrong J-code triggers automated denial. See disambiguation section.
Phase 1 Identify what you're billing Confirm HER2 status, indication (mBC vs KATHERINE adjuvant), dose, and that the order is Kadcyla — not Enhertu.

Kadcyla (T-DM1) vs Enhertu (T-DXd) — disambiguation FDA labels verified May 2026

Same HER2 target. Different payload, dose, J-code, and eligibility. Easy to confuse at order entry — high-impact to confuse at claim entry.

AttributeKadcyla (this page)Enhertu
Generic / development nameado-trastuzumab emtansine (T-DM1)fam-trastuzumab deruxtecan-nxki (T-DXd)
HCPCSJ9354J9358
ManufacturerGenentech (Roche)Daiichi Sankyo / AstraZeneca
Antibody backboneTrastuzumabTrastuzumab
Cytotoxic payloadDM1 (mertansine; maytansinoid microtubule inhibitor)DXd (deruxtecan; topoisomerase-I inhibitor, exatecan derivative)
Drug-antibody ratio (DAR)~3.5~8
Bystander effectLimited (non-membrane-permeable payload)Pronounced (membrane-permeable payload — enables HER2-low / ultralow activity)
Standard dose3.6 mg/kg q3w5.4 mg/kg q3w (6.4 for gastric/GEJ)
HER2 eligibilityHER2+ only (IHC 3+ or 2+/ISH+)HER2+, HER2-low, HER2-ultralow, HER2-mutant NSCLC, HER2+ tumor-agnostic
Approved indicationsHER2+ mBC (2L+) · HER2+ early-stage with residual disease post-neoadjuvant (KATHERINE, 14-cycle)Six indications across breast, gastric, NSCLC, and tumor-agnostic solid tumors
Key boxed warningsHepatotoxicity · LV dysfunction · embryo-fetalILD/pneumonitis (~12%) · embryo-fetal
Q2 2026 ASP+6%/mg$42.198 (live-bound)$31.262
2L HER2+ mBC standard of care?Historically yes; displaced by Enhertu per DESTINY-Breast03Currently preferred 2L per NCCN
The trap: Order sets, EHR favorites, and pharmacy worklists sometimes still default "T-DM1" and "T-DXd" to the same item or use ambiguous "trastuzumab ADC" wording. Always confirm brand name (Kadcyla vs Enhertu) AND J-code (J9354 vs J9358) AND dose (3.6 vs 5.4 mg/kg) at order entry, pharmacy verification, and claim coding. A wrong-J-code claim will deny for missing PA on the actual drug administered.
Where Kadcyla is still preferred:
  • KATHERINE adjuvant indication — HER2+ early-stage breast cancer with residual invasive disease after neoadjuvant taxane + trastuzumab. Kadcyla × 14 cycles is the standard of care; Enhertu is not approved here (DESTINY-Breast05 is reading out).
  • 2L+ mBC patients who failed or are ineligible for Enhertu — particularly with significant pulmonary comorbidity that contraindicates Enhertu's ILD risk.
  • Patients with prior Enhertu ILD who need ongoing HER2-directed therapy.

Cross-link: Enhertu (J9358) billing & coding · Herceptin / trastuzumab biosimilars (J9355) · Perjeta / pertuzumab (J9306).

Dosing matrix FDA label verified May 2026

Single dose level (3.6 mg/kg q3w) for both approved indications. Cycle count differs.

IndicationDoseScheduleCourse lengthHER2 requirement
HER2+ metastatic breast cancer (post-Herceptin + taxane, 2L+) 3.6 mg/kg IV q3w Until progression or unacceptable toxicity IHC 3+ or 2+/ISH+
HER2+ early-stage breast cancer with residual invasive disease post-neoadjuvant taxane + trastuzumab (KATHERINE) 3.6 mg/kg IV q3w 14 cycles total IHC 3+ or 2+/ISH+
Maximum dose cap: Per FDA label, do NOT exceed 3.6 mg/kg per dose. For very high-weight patients, calculate based on actual body weight (not ideal or adjusted) unless institutional protocol specifies otherwise. Do not substitute Kadcyla for Herceptin (trastuzumab, J9355) on a mg-for-mg basis — they are different drugs with different dosing schedules and different vial sizes.

Infusion timing — cycle 1 vs cycles 2+

  • Cycle 1: infuse over 90 minutes. Observe patient during infusion and for at least 90 minutes after for fever, chills, or other infusion-related reactions. Bill 96413 + 96415 × 1.
  • Cycles 2+ if cycle 1 tolerated: infuse over 30 minutes. Observe at least 30 minutes post-infusion. Bill 96413 only.
  • Use a 0.20- or 0.22-micron in-line polyethersulfone (PES) filter for IV administration.
  • Slow or interrupt the infusion for any infusion-related reaction. Permanently discontinue for life-threatening reactions.

Worked unit-math example — 70 kg HER2+ mBC patient (3.6 mg/kg q3w)

# Dose calculation
70 kg × 3.6 mg/kg = 252 mg administered
Vial combination: 1 × 100 mg + 1 × 160 mg = 260 mg drawn (minimum-waste choice)
Waste: 260 - 252 = 8 mg

# Billing
Drug line 1: 252 units J9354 with JZ modifier (administered)
Drug line 2: 8 units J9354 with JW modifier (discarded)
Admin: 96413 (cycles 2+) or 96413 + 96415 (cycle 1)

# Q2 2026 reimbursement
260 mg billed × $42.198/mg = ~$10,971.48 per cycle
Annual mBC (~17 cycles q3w) ≈ ~$186,515 before sequestration
KATHERINE adjuvant total (14 cycles) ≈ ~$153,601

Worked example — 85 kg KATHERINE adjuvant patient (3.6 mg/kg q3w)

# Dose calculation
85 kg × 3.6 mg/kg = 306 mg administered
Vial combination: 1 × 160 mg + 2 × 100 mg = 360 mg drawn
Alternative: 2 × 160 mg = 320 mg drawn → only 14 mg waste (preferred)
Waste (preferred): 320 - 306 = 14 mg

# Billing
Drug line 1: 306 units J9354 with JZ modifier (administered)
Drug line 2: 14 units J9354 with JW modifier (discarded)
Total billed: 320 units × $42.198/mg = ~$13,503.36 per cycle
14-cycle total ≈ ~$189,047
Vial-combination strategy minimizes waste. With both 100 mg and 160 mg vials on the shelf, pharmacy should always pick the combination that comes closest to (but at or above) the calculated dose. Document the chosen combination + waste rationale in the pharmacy record. JW reimbursement requires the waste line, but payer audits also look for a defensible "we picked the smallest combination" rationale.

NDC reference FDA NDC Directory + Genentech 2026

NDC (10/11-digit)StrengthPackage SizeUnits/Vial
50242-088-01 / 50242-0088-01 100 mg Single-dose vial; 1 vial per carton 100 units (1 mg = 1 unit)
50242-087-01 / 50242-0087-01 160 mg Single-dose vial; 1 vial per carton 160 units (1 mg = 1 unit)
Reconstitution & stability:
  • 100 mg vial: reconstitute with 5 mL Sterile Water for Injection → 20 mg/mL.
  • 160 mg vial: reconstitute with 8 mL Sterile Water for Injection → 20 mg/mL.
  • Swirl gently — do NOT shake. Allow to stand to clear residual foam; reconstituted solution should be clear to slightly opalescent and colorless to pale brown.
  • Dilute the calculated dose in 250 mL of 0.9% Sodium Chloride Injection USP. Do NOT use 5% dextrose — will degrade Kadcyla.
  • Use within in-use stability times per current FDA label; refrigerate if storage is required.
Two-vial inventory standard. Sites that stock only the 100 mg vial waste more drug per dose. Sites that stock only the 160 mg vial waste more drug at low-weight patients. Carrying both vial strengths is the standard inventory pattern for Kadcyla.
Phase 2 Code the claim 96413 + 96415 cycle 1, 96413-only cycles 2+. JZ on administered line, JW on waste line.

Administration codes CPT verified May 2026

Kadcyla is billed as chemotherapy administration despite being an ADC.

CodeDescriptionWhen to use
96413 Chemotherapy administration, IV infusion technique; up to 1 hour, single or initial substance/drug Primary code, every cycle. Covers the first 1 hour of infusion (the full 30-minute cycle-2+ infusion fits within this code).
96415 Chemotherapy administration, IV infusion; each additional hour Cycle 1 only — pair with 96413 to cover the 90-minute first infusion (1 unit of 96415 covers the second 60 minutes / portion thereof).
96365 / 96366 Therapeutic IV infusion (non-chemo) NOT appropriate. Kadcyla is an antibody-drug conjugate; CPT classifies ADC admin under chemo codes regardless of mechanism. Pays materially less and triggers downcode denial.
Antiemetic / hydration admin 96367 (sequential), 96368 (concurrent), or 96375 (IV push) For pre-medication. Kadcyla has low-moderate emetogenicity — most regimens use prn antiemetics rather than mandatory pre-medication. Document per institutional protocol.
Why chemo admin for an ADC: CPT chemotherapy administration codes (96409–96425) apply to complex monoclonal antibody and ADC administration regardless of mechanism. Kadcyla pays materially more under 96413 + 96415 than under 96365 therapeutic infusion, and the chemo-admin code aligns with how every major payer expects ADC administration to be billed.

Modifiers CMS verified May 2026

JW — required for any partial-vial waste

Kadcyla is weight-based and ships only as 100 mg and 160 mg single-dose vials. Most calculated doses will not match a clean combination of vials. Bill the discarded portion on a separate J9354 claim line with the JW modifier. Example: a 70 kg patient at 3.6 mg/kg needs 252 mg → 1 × 100 mg + 1 × 160 mg = 260 mg drawn → 8 mg waste. Two lines: 252 units with JZ + 8 units with JW.

JZ — on the administered-units line

Effective July 1, 2023, CMS requires either JZ (no waste) or JW (waste) on every single-dose container claim. For Kadcyla, the administered-units line carries JZ; the waste line carries JW. One of JZ or JW must be on every J9354 claim. Submitting J9354 without a modifier is a guaranteed denial.

Modifier 25 — same-day E/M

Use modifier 25 on the E/M code when a significant, separately identifiable evaluation and management service is performed on the same day as the infusion (e.g., a hepatotoxicity follow-up visit, LVEF review, or treatment-plan modification). Routine pre-infusion clinical assessment is bundled into the admin code.

340B modifiers (JG, TB)

For 340B-acquired Kadcyla, follow your MAC's current 340B modifier policy. Hospital outpatient claims under the OPPS 340B payment policy require the appropriate JG or TB modifier per CMS instructions and your hospital's 340B program participation.

Common error: Forgetting the JW waste line. CMS audits frequently catch missing waste documentation on weight-based oncology biologics. The waste is reimbursable — not reporting it is leaving money on the table while still risking an audit finding. Document waste in the pharmacy compounding record (mg discarded + vial combination chosen).
Worked modifier example (70 kg patient, 3.6 mg/kg):
  • Line 1 (administered): J9354 × 252 units with JZ modifier
  • Line 2 (waste): J9354 × 8 units with JW modifier
  • Line 3 (admin cycle 1): 96413 × 1 + 96415 × 1
  • Line 4 (admin cycles 2+): 96413 × 1 only

ICD-10-CM by indication FY2026 verified May 2026

Both Kadcyla indications are HER2+ breast cancer. Use the C50.x site-specific code with appropriate laterality, plus mets coding for metastatic disease, plus the Z-code for HER2-positive status where applicable.

Indication / scenarioICD-10Notes
HER2+ malignant neoplasm of breast (primary site) C50.011-C50.929 4th digit = anatomic subsite (nipple, central, upper-inner, etc.). 5th digit = laterality (1 right, 2 left, 9 unspecified). 6th digit = sex (1 female, 2 male).
Metastatic disease — secondary sites (mBC indication) C77.x, C78.x, C79.x Code all known metastatic sites: lymph nodes (C77.x), lung (C78.0x), liver (C78.7), bone (C79.51), brain (C79.31), etc. Required for mBC PA.
Personal history of breast cancer (residual disease post-neoadjuvant scenarios) Z85.3 Used selectively with KATHERINE-adjuvant patients per encounter type. Not a stand-alone PA code.
HER2-positive status / receptor expression Z17.0 (estrogen receptor positive) where applicable HER2-specific Z-code does not currently exist; HER2+ status is documented in the pathology report and the PA narrative. Most payers do NOT require a separate Z-code for HER2 status but DO require the path report.
Encounter for antineoplastic chemotherapy Z51.11 Primary encounter code on the day of infusion, paired with C50.x.
Encounter for antineoplastic immunotherapy Z51.12 Some payers prefer Z51.12 for ADCs — verify per payer guidance. Most still accept Z51.11.
HER2+ status is the gate, but it lives in pathology — not ICD-10. The ICD-10 code alone does not establish HER2-positivity. Every Kadcyla PA must include the HER2 IHC/ISH pathology report (IHC 3+ or IHC 2+/ISH+). For the KATHERINE adjuvant indication, also include the post-surgical pathology report showing residual invasive disease in the breast or axillary nodes after neoadjuvant taxane + trastuzumab therapy.
Staging Z-codes for KATHERINE: Per payer norms, document the original pre-neoadjuvant clinical stage and the post-neoadjuvant pathologic stage (ypTNM). The residual-disease finding is what unlocks Kadcyla adjuvant eligibility; payer review staff will look for the ypT/ypN call in the surgical pathology report.

Site of care & place of service Verified May 2026

UnitedHealthcare, Aetna, and most major BCBS plans run site-of-care utilization management for high-cost oncology biologics. Kadcyla falls in scope. The 90-minute cycle 1 infusion typically permits HOPD, but the 30-minute cycles 2+ are increasingly steered into office, ASC, or ambulatory infusion suite settings.

SettingPOSClaim formPayer steering
Physician oncology office11CMS-1500 / 837PPreferred by commercial UM
Ambulatory infusion suite (AIC)49CMS-1500 / 837PPreferred by commercial UM
Oncology ASC24CMS-1500 / 837PAcceptable
Hospital outpatient (on-campus)22UB-04 / 837IDisfavored after cycles 1-2 on commercial plans
Hospital outpatient (off-campus PBD)19UB-04 / 837IDisfavored after cycles 1-2
Patient home12CMS-1500 (with home infusion)Generally not appropriate — LVEF / LFT monitoring + infusion-reaction risk make supervised setting standard
Cycle 1 site-of-care exception: Most payers allow HOPD or higher-acuity settings for cycle 1 because of the 90-minute infusion plus 90-minute post-infusion observation. Site-of-care steering typically activates starting cycle 2 or 3 for cycles that should fit cleanly into office or AIC settings (30-min infusion + 30-min observation).

Claim form field mapping Genentech Access Solutions 2026

From the Kadcyla HCP coding & coverage materials and Genentech Access Solutions billing guide.

InformationCMS-1500 boxNotes
NPI17bRendering provider
NDC qualifier + 11-digit NDC + UoM + qty24A shaded areaN4 + carton NDC (100 mg 50242-0088-01 and/or 160 mg 50242-0087-01) + ML + total reconstituted volume drawn per vial used. List each vial NDC used.
HCPCS J9354 + JZ (administered units)24D (drug line 1)Actual mg administered, weight-based
HCPCS J9354 + JW (waste units)24D (drug line 2)Discarded mg from partial vial — nearly always present
Drug units24GPer line: administered mg (line 1), waste mg (line 2)
CPT 96413 (admin line)24DFirst hour, every cycle
CPT 96415 × 1 (cycle 1 only)24D (admin line, cycle 1)Each additional hour — for the 90-minute cycle 1 infusion
ICD-1021C50.x (primary) + mets coding (mBC) or ypTNM-documented residual disease (KATHERINE) + Z51.11/Z51.12
HER2 biomarker test claim line (separate, when first done)24DCPT 88360/88361 (HER2 IHC), 88374/88377 (HER2 ISH FISH/CISH)
PA number23Required by all major commercial payers
NDC reporting with combined vials: When a single dose is drawn from both a 100 mg and a 160 mg vial, most payers expect each vial NDC to appear on the claim with the volume drawn from that vial. Pharmacy compounding records should show which NDCs were used per dose. Some clearinghouses accept a single NDC line for the larger vial — verify with payer / clearinghouse guidance.
Phase 3 Get paid HER2 path report on file + (for KATHERINE) post-neoadjuvant residual-disease pathology are the make-or-break PA elements.

Payer policy snapshot Reviewed May 2026

All major payers require HER2 documentation matched to indication. For KATHERINE adjuvant, surgical pathology showing residual invasive disease is the additional unlock.

PayerPA?Biomarker enforcementSite-of-care UM
UnitedHealthcare
Oncology Med Coverage Policy		 Yes Strict — HER2 IHC + ISH report required; for KATHERINE, post-neoadjuvant residual-disease pathology required Aggressive: Optum-managed program steers Kadcyla out of HOPD after cycles 1-2
Aetna
CPB 0244 + Medical Drug policies		 Yes HER2 IHC 3+ or 2+/ISH+ required; KATHERINE adjuvant requires explicit residual invasive disease documentation Yes (separate Site-of-Care policy)
BCBS plans
Vary by plan		 Yes Generally aligned with NCCN Breast Cancer guideline + FDA label HER2 requirements Plan-specific; most have oncology biologic site-of-care steering for HER2+ regimens
Medicare (MAC LCDs)
All MACs		 Generally no PA under Original Medicare Coverage for FDA-approved on-label indications with appropriate ICD-10 + HER2 documentation N/A (Original Medicare). MA plans may apply commercial-style UM.
Medicaid (state-by-state) Yes (most states) HER2 + indication-matched documentation; state PDL may require step therapy Limited; state-specific

HER2 biomarker test billing (separate from drug claim)

TestCPTFor Kadcyla
HER2 IHC (manual)88360Primary HER2 protein expression test — IHC 3+ qualifies without reflex
HER2 IHC (computer-assisted)88361Alternative to 88360
HER2 FISH (in situ hybridization)88374Required for IHC 2+ (equivocal) reflex — determines HER2+ amplified vs not
HER2 CISH88377Alternative ISH method
HER2 dual-probe FISH (newer codes)88373 / 88377Verify per lab; payer may require dual-probe

Step therapy

For HER2+ mBC, most payers require documentation of prior trastuzumab + a taxane (separately or in combination) before approving Kadcyla. Many commercial payers now also require failure of or intolerance to Enhertu (T-DXd) per the DESTINY-Breast03 preferred-2L pattern — verify per payer policy in 2026. For the KATHERINE adjuvant indication, step therapy is the prior neoadjuvant regimen itself: taxane + trastuzumab (with or without pertuzumab) followed by surgical pathology showing residual invasive disease.

Medicare reimbursement CMS Q2 2026 (live)

Quarterly ASP from CMS Part B Drug Pricing File. Refreshes automatically each quarter.

Q2 2026 payment snapshot — J9354

Effective April 1 – June 30, 2026 · Based on 4Q25 ASP submissions · ASP updated quarterly by CMS — next update July 1, 2026 for Q3

ASP + 6%
$42.198
per mg / per unit
252 mg administered (70 kg, 3.6 mg/kg)
$10,633.90
252 units × ASP+6%
260 mg billed (with JW waste)
$10,971.48
260 units × ASP+6% (admin + waste)
Annualized cost (70 kg patient at 3.6 mg/kg q3w): ~17 cycles/year × $10,971.48 (with waste) = ~$186,515/year mBC (Medicare ASP+6%). After ~2% sequestration: ~$182,800/year actual paid. KATHERINE adjuvant course (14 cycles total): ~$153,600.72. Heavier patients are materially higher.

Coverage

No NCD specific to ado-trastuzumab emtansine. Coverage falls under MAC LCDs for biologics and the generic drug-coverage framework. All MACs cover J9354 for FDA-approved on-label indications with appropriate ICD-10 and HER2 documentation. Medicare Advantage plans may apply commercial-style PA and site-of-care UM.

Code history

  • J9354 — permanent code, "Inj, ado-trastuzumab emt 1mg" (initial FDA approval was February 22, 2013; pre-permanent-code period used unclassified J3490 / J9999)
  • Indication expansion: KATHERINE adjuvant (May 3, 2019) — no new J-code required; same J9354 used

Patient assistance — Genentech Access Solutions Verified May 2026

  • Genentech Access Solutions (Kadcyla hub): 1-866-422-2377 / genentech-access.com — benefits investigation, prior authorization assistance, appeal support, billing & coding hotline
  • Genentech Oncology Co-pay Assistance Program: commercial copay support up to $25,000/year for eligible commercially-insured patients (excludes Medicare, Medicaid, federal program patients)
  • Genentech Patient Foundation: free product for uninsured / underinsured patients meeting income requirements (typically ~≤ 500% FPL; documented annually)
  • Foundations for Medicare patients: refer to PAN Foundation (Breast Cancer fund), HealthWell Foundation, CancerCare Co-Payment Assistance Foundation — verify open breast oncology funds quarterly
  • Web: genentech-access.com/hcp/brands/kadcyla.html / kadcyla.com
Need to model what a specific patient will actually pay after copay assistance, deductible, coinsurance, and OOP max? Run a CareCost Estimate — J9354 pre-loaded.
Phase 4 Fix problems Missing HER2 path report, missing KATHERINE residual-disease pathology, missing LFT/LVEF baseline, and missing JW waste line are the top four denials.

Common denials & how to fix them

Denial reasonCommon causeFix
HER2 documentation not on file PA submitted without HER2 IHC/ISH pathology report Submit HER2 IHC (and ISH reflex if IHC 2+) path report. Schedule HER2 testing FIRST when starting a new patient on Kadcyla — this is the #1 cause of Kadcyla denials.
HER2 tier mismatch (HER2-low / HER2-ultralow) Provider ordered Kadcyla for a HER2-low (IHC 1+ or 2+/ISH-) or HER2-ultralow patient Kadcyla is HER2+ only (IHC 3+ or 2+/ISH+). HER2-low / HER2-ultralow patients should go to Enhertu. Re-verify path report and switch drug if appropriate.
Wrong drug billed (Enhertu vs Kadcyla) Order or claim used wrong J-code (J9354 vs J9358), wrong brand name, or wrong dose (3.6 vs 5.4 mg/kg) Confirm brand + J-code + dose at order entry, pharmacy verification, and claim coding. Resubmit with correct drug. See disambiguation section.
Missing prior HER2-directed therapy (mBC) HER2+ mBC PA without documentation of prior trastuzumab + taxane Submit clinical history showing prior trastuzumab (or biosimilar) + prior taxane (paclitaxel, docetaxel, or nab-paclitaxel). In 2026, some payers also require failure / intolerance of Enhertu first — verify policy.
Missing KATHERINE residual-disease documentation Adjuvant PA without post-neoadjuvant surgical pathology showing residual invasive disease Submit surgical pathology report explicitly documenting residual invasive disease in the breast (ypT1+) or axillary nodes (ypN1+) after neoadjuvant taxane + trastuzumab. The ypTNM call is what unlocks coverage.
Missing LFT or LVEF baseline documentation Hepatotoxicity / LV-dysfunction boxed warnings not documented at baseline Document baseline AST, ALT, total bilirubin, alkaline phosphatase, and baseline LVEF (echo or MUGA) in the chart. Include per-cycle LFTs and q3-month LVEF assessments for continuation reviews.
Wrong admin code (96365) Therapeutic IV billed instead of chemo IV Resubmit with 96413 (+ 96415 for cycle 1). Kadcyla is chemo admin per CPT classification despite ADC mechanism.
JW waste line missing Wasted mg from partial vial not reported Add JW line for discarded units alongside the JZ line for administered units. Required since 7/1/2023. Document vial combination + waste in pharmacy compounding record.
JZ/JW missing entirely Single-dose vial claim without modifier One of JZ or JW must be on every J9354 claim. Resubmit with appropriate modifiers per the unit math.
Wrong NDC format (vial-level only) Vial NDC submitted in wrong format (missing leading 0) or only one vial NDC when both used Use 11-digit format: 50242-0088-01 (100 mg) and/or 50242-0087-01 (160 mg). List both NDCs when both vials are used in the dose.
Site of care (HOPD after cycles 1-2) HOPD administration after cycle 2-3 on commercial plan with site-of-care UM Move to office (POS 11) or AIC (POS 49). Submit medical necessity letter if HOPD required (e.g., active LV dysfunction monitoring, recent hepatotoxicity event).
Dose exceeds 3.6 mg/kg per cycle Calculation error or dose-cap violation Per FDA label, do NOT exceed 3.6 mg/kg per dose. Recalculate based on actual body weight; document weight, calculation, and chosen dose in chart and re-submit.

Frequently asked questions

What is the HCPCS code for Kadcyla?

Kadcyla (ado-trastuzumab emtansine, T-DM1) is billed under HCPCS J9354 — "Inj, ado-trastuzumab emt 1mg." Each milligram equals one billable unit. Dosing is weight-based at 3.6 mg/kg IV every 3 weeks for both HER2-positive metastatic breast cancer (after Herceptin + a taxane) and HER2-positive early-stage breast cancer with residual invasive disease after neoadjuvant taxane + trastuzumab therapy (KATHERINE indication, 14-cycle adjuvant course). The drug ships as 100 mg and 160 mg single-dose lyophilized vials.

Kadcyla vs Enhertu — when do I choose which?

Both target HER2 but they are clinically and pharmacologically distinct ADCs. Kadcyla (J9354, T-DM1) uses the DM1 maytansinoid payload, is dosed 3.6 mg/kg q3w, and is the standard adjuvant therapy for HER2+ early-stage breast cancer with residual disease after neoadjuvant treatment (KATHERINE), and a 2L option for HER2+ metastatic breast cancer. Enhertu (J9358, T-DXd) uses the deruxtecan topoisomerase-I inhibitor payload, is dosed 5.4 mg/kg q3w (6.4 for gastric), and has displaced Kadcyla as preferred 2L for HER2+ mBC per DESTINY-Breast03 and now covers HER2-low, HER2-ultralow, HER2-mutant NSCLC, and HER2+ tumor-agnostic populations. They are NOT interchangeable on the claim — confirm brand, J-code, and dose at order entry.

Is HER2 testing required for Kadcyla?

Yes — Kadcyla requires documented HER2-positive status by an FDA-approved test (IHC 3+ OR IHC 2+ with ISH-positive amplification) on either the primary tumor or, where appropriate, the metastatic biopsy. HER2-low and HER2-ultralow patients are NOT eligible for Kadcyla (that population is Enhertu-only). Schedule HER2 IHC and reflex ISH BEFORE submitting the Kadcyla prior authorization; PA submitted without a HER2 result on file is the single most common denial reason.

Am I eligible for Kadcyla after neoadjuvant therapy with residual disease?

Yes — the FDA expanded Kadcyla's label on May 3, 2019 (based on the KATHERINE trial) to include adjuvant treatment of patients with HER2-positive early breast cancer who have residual invasive disease after neoadjuvant taxane and trastuzumab-based therapy. Payer PA requires three documents: (1) surgical pathology showing residual invasive disease in the breast or axillary nodes, (2) prior neoadjuvant regimen documentation (taxane + trastuzumab ± pertuzumab), and (3) HER2+ status. The KATHERINE indication is a 14-cycle adjuvant course.

What CPT do I bill for T-DM1 infusion?

CPT 96413 (chemo IV, first hour) plus 96415 (each additional hour) for cycle 1 only (90-minute infusion). Cycles 2+ use only 96413 (30-minute infusion if cycle 1 was tolerated). Kadcyla is an antibody-drug conjugate billed under chemo admin codes per CPT/AMA classification. Do NOT bill 96365 (therapeutic IV) — it pays less and is the wrong code.

What hepatotoxicity monitoring does Kadcyla require?

Kadcyla carries a BOXED WARNING for hepatotoxicity, including rare fatal hepatic failure. Per FDA label: monitor liver function (AST, ALT, total bilirubin, alkaline phosphatase) before initiation, before each dose, and as clinically indicated. Hold or permanently discontinue Kadcyla for transaminase or bilirubin elevations per label-specified thresholds. Nodular regenerative hyperplasia of the liver has also been reported. Document baseline LFTs and per-cycle LFTs in the chart — payer audits frequently look for this. Two additional boxed warnings apply: left ventricular dysfunction (assess LVEF at baseline and every 3 months) and embryo-fetal toxicity.

What is the Medicare reimbursement for J9354?

For Q2 2026, the Medicare Part B payment limit for J9354 is $42.198 per mg (ASP + 6%). For a 70 kg patient at 3.6 mg/kg (252 mg administered + 8 mg waste from a 100 mg + 160 mg vial combination = 260 mg billed), reimbursement is approximately $10,971.48 per cycle. Annualized at q3w (~17 cycles/year): approximately $186,515 mBC. KATHERINE adjuvant total (14 cycles): approximately $153,601. After ~2% sequestration: roughly $182,800/year actual paid for mBC.

Is Kadcyla approved in pediatric patients?

No. The safety and effectiveness of Kadcyla have not been established in pediatric patients. All approved indications (metastatic HER2+ breast cancer and the KATHERINE adjuvant indication for early-stage HER2+ breast cancer with residual disease post-neoadjuvant) are limited to adults. Kadcyla is not used in pediatric oncology.

Reference Sources & methodology Every claim on this page is sourced. Methodology and review history below.

Source documents

  1. Genentech Access Solutions — Kadcyla Coding & Reimbursement HCP page
    Document footer: Genentech Access Solutions 2026
  2. DailyMed — KADCYLA (ado-trastuzumab emtansine) Prescribing Information
    FDA-approved label, most recent revision (BLA 125427)
  3. FDA Drugs@FDA — Kadcyla BLA 125427 approvals & supplements
    Initial approval February 22, 2013 (mBC). KATHERINE indication added May 3, 2019.
  4. CMS — Medicare Part B Drug ASP Pricing File
    Q2 2026 quarterly file, effective April 1 – June 30, 2026 (J9354 = $42.198/mg)
  5. SEER CanMED — HCPCS J9354 reference
  6. Verma et al., EMILIA: trastuzumab emtansine for HER2-positive advanced breast cancer (NEJM 2012)
    Pivotal trial establishing 3.6 mg/kg q3w dosing and 2L mBC efficacy
  7. von Minckwitz et al., KATHERINE: trastuzumab emtansine for residual invasive HER2-positive breast cancer (NEJM 2019)
    Pivotal trial supporting May 3, 2019 adjuvant indication expansion
  8. UnitedHealthcare — Oncology Medication Clinical Coverage Policy
  9. Aetna CPB 0244 — HER2-targeted therapies (covers ado-trastuzumab emtansine)
  10. NCCN Clinical Practice Guidelines — Breast Cancer (HER2+ sections, including KATHERINE-aligned adjuvant)
  11. Genentech — Kadcyla HCP product page (PI, dosing, REMS, safety)
  12. FDA National Drug Code Directory

About this page

We maintain this page as a living reference. Medicare ASP pricing is bound to our underlying CareCost data layer and refreshes automatically when CMS publishes new quarterly files. Coding and policy content is reviewed at least quarterly and updated whenever a source document changes. Kadcyla's label has been stable since the May 2019 KATHERINE expansion; the more dynamic content on this page is the 2L mBC positioning relative to Enhertu (T-DXd), which has shifted significantly with DESTINY-Breast03.

Found an error? Email hello@carecostestimate.com.

Refresh cadence

ElementCadenceHow it's refreshed
Medicare ASP pricingQuarterlyAuto-bound to CareCost ASP layer; updates on CMS file release.
Payer policies (UHC, Aetna, BCBS) including Enhertu-first step therapy postureSemi-annualManual review against published payer policy documents.
HCPCS / CPT / modifier rules + HER2 biomarker test codesAnnualReviewed against CMS HCPCS quarterly files, AMA CPT releases.
NDC, dosing, FDA label, indication list, boxed warning textEvent-drivenTied to Genentech document version + FDA label revision date.

Reviewer

Pending SME review. This page is staff-authored from primary sources (FDA, CMS, Genentech, payer documents — all linked above). Editorial review in progress. Until that review is complete, treat this as a draft reference and verify each cited source for high-stakes claims — especially the Kadcyla vs Enhertu 2L positioning, which evolves with each NCCN update.

Change log

  • — Initial publication + SME audit pass. ASP data: Q2 2026 ($42.198/mg) verified against CMS file. Manufacturer source: Genentech Access Solutions 2026. FDA label re-verified via DailyMed: most recent revision. Two approved indications: HER2+ mBC (Feb 22, 2013, EMILIA) and KATHERINE adjuvant (May 3, 2019, residual invasive disease post-neoadjuvant taxane + trastuzumab). Three boxed warnings (hepatotoxicity, LV dysfunction, embryo-fetal toxicity) re-confirmed. Heavy disambiguation against Enhertu (J9358, T-DXd).

Methodology

Every claim on this page is sourced inline. Pricing reflects the current CMS Part B Drug ASP Pricing File. Payer policies are read directly from each payer's published medical/pharmacy policy documents. Indication list, dosing, and boxed warning content are verified against the current FDA label revision. We do not paraphrase from billing-software vendor blogs.

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