HCPCS code S0170 – Anastrozole oral 1 mg billing guide

Key takeaways

S0170 covers anastrozole, oral, 1 mg, so one unit equals one tablet and a 30-tablet fill is billed as 30 units.

Medicare Part B does not accept S-series codes, so Medicare patients get anastrozole through a Part D pharmacy claim billed by NDC.

Some Medicaid programs and commercial payers accept S0170, but many require an NDC-based pharmacy claim instead. Verify with each payer.

Practice software such as Pabau submits S0170 claims and tracks each claim’s status, which cuts manual re-entry for billing staff.

HCPCS Code S0170: definition and code details

HCPCS Code S0170 is an S-series HCPCS Level II code with the official descriptor Anastrozole, oral, 1 mg. One billing unit equals one 1 mg tablet. S-series codes are temporary national codes that CMS maintains for state Medicaid programs and commercial payers.

Unlike most J-codes, which report Part B drugs, S-codes are not recognized by Medicare’s Part B benefit. According to the CMS HCPCS overview, S-series codes exist to meet the coding needs of non-Medicare payers.

S0170 sent to Part B is denied because it sits outside Medicare’s recognized Level II set. Medicare patients get anastrozole through a Part D prescription drug claim instead.

Anastrozole: clinical background and billing context

Anastrozole is an aromatase inhibitor approved by the FDA for hormone receptor-positive (HR+) breast cancer in both the adjuvant (post-surgery) and advanced (metastatic) settings. It works by blocking the enzyme aromatase, reducing estrogen production, and slowing tumor growth in ER-positive cancers.

Anastrozole is an oral tablet taken once daily. Because patients take it at home, it does not qualify as a Medicare Part B incident-to drug. That is why S0170 exists as an oral drug code for non-Medicare payers, and why Medicare routes this drug through Part D instead.

S0170 code at a glance

The reference table below covers the billing attributes coders need before submitting HCPCS Code S0170 claims.

Which payers accept HCPCS Code S0170?

Some Medicaid programs and commercial payers accept S0170, but many require an NDC-based pharmacy claim instead, so verify with each payer. S-series codes are not part of the Medicare Part B fee schedule, and CMS does not publish a Part B allowable rate for them.

Medicare Part B vs Part D: where does anastrozole fit?

Anastrozole belongs under Medicare Part D, the prescription drug benefit. Oral drugs that patients take at home are covered there, not as incident-to infusions or injections under Part B’s medical benefit. Submitting S0170 to Medicare Part B is a coverage mismatch that generates an automatic denial.

Many states have oral chemotherapy parity laws that require commercial insurers to cover oral oncolytics at the same cost-sharing level as intravenous chemotherapy. These laws shape what the patient pays, not what goes on the claim, and they do not change Medicare’s benefit rules.

For Medicare beneficiaries, the pharmacy dispenses anastrozole and submits a Part D drug claim using the National Drug Code (NDC), not S0170.

How to bill S0170: units, NDC, and documentation

S0170 billing starts with the unit convention, whichever claims software for practices submits the claim. One unit equals one milligram of anastrozole, and the standard tablet is 1 mg, so one unit equals one tablet.

A 30-day supply is billed as 30 units, and a 90-day supply as 90 units. Underbilling the unit count is a frequent error on anastrozole claims.

1. Confirm the payer accepts S0170. Not every commercial plan or Medicaid program uses S-series codes, so check the payer billing manual before submitting. If the payer does not accept S0170, use J8999 (prescription drug, oral, chemotherapeutic, NOS) or bill by NDC per the payer’s instructions.
2. Calculate units from the dispensed quantity. Count the total milligrams dispensed. A 30-tablet fill = 30 units. A 90-tablet fill = 90 units. Enter the unit count in Box 24G on the CMS-1500 form.
3. Attach the 11-digit NDC. Most Medicaid programs and many commercial payers require the National Drug Code on the claim. Use the format N4XXXXXXXXXXX followed by the unit qualifier (UN for each tablet unit) in the NDC field. Omitting the NDC is a frequent denial reason.
4. Include the prior authorization number. If the payer required PA and you have the approval number, enter it in Box 23 of the CMS-1500. Missing or expired PA numbers trigger prior-auth denials.
5. Link a valid ICD-10 diagnosis code. The diagnosis must support the medical necessity of anastrozole. See the ICD-10 section below for accepted codes.
6. Submit on CMS-1500. Outpatient and physician dispensing uses CMS-1500. Hospital outpatient dispensing may use UB-04 depending on facility policy.

Our guide to medical billing workflows shows how a claim moves from charge entry to payment, and where these six steps fit.

Required ICD-10 diagnosis codes for S0170

Payers require a linked diagnosis code that supports the medical necessity of anastrozole. The table below covers the ICD-10-CM codes most commonly submitted with HCPCS Code S0170.

Specificity matters. An unspecified C50 code used when laterality is documented rarely causes a denial, but audits flag unspecified codes when the record contains the detail. Coders should always capture the most specific code the documentation supports.

Prior authorization requirements for anastrozole

Prior authorization for anastrozole is required by many commercial payers and some state Medicaid programs, though requirements vary by plan and policy year. Practices billing HCPCS Code S0170 regularly should verify PA status for each patient’s plan before dispensing.

Common PA criteria for anastrozole include confirmation of HR+ breast cancer status (usually a pathology report) and the treatment setting (adjuvant or advanced). Some plans also want evidence that tamoxifen was considered or contraindicated. The prescriber’s NPI and specialty are also typically required on PA requests for oncology drugs.

• Gather the pathology report confirming hormone receptor-positive status before initiating the PA request.
• Document the treatment line (first-line adjuvant, second-line metastatic) in the clinical notes and PA submission form.
• Note tamoxifen history if the plan requires evidence that prior hormonal therapy was tried or contraindicated.
• Record the PA approval number and expiration date. Anastrozole is typically prescribed for five or more years, so PA renewals are common. A missed renewal date generates a denial on an otherwise clean claim.
• Verify NDC on the approved drug list. Some plans approve anastrozole generically but require a specific NDC (usually the lowest-cost generic) to be dispensed and billed.

S0170 fee schedule and reimbursement rates

There is no published Medicare Part B fee schedule rate for HCPCS Code S0170 because S-series codes are outside the Medicare Part B allowable set. Reimbursement rates for S0170 are set individually by each payer.

Medicaid reimbursement for anastrozole typically follows the state’s drug pricing basis. The most common bases are Average Wholesale Price (AWP) minus a percentage discount, or Maximum Allowable Cost (MAC) pricing. Rates differ by state and are published in each state’s Medicaid fee schedule. Commercial payer rates reflect contracted formulary pricing and vary by plan tier.

For current payer-specific rates, check the payer’s online fee schedule portal or ask the plan’s provider relations team. S0170 reimbursement reflects each payer’s contracted rate for the oral drug rather than a CMS-published national rate. The AAPC HCPCS code reference helps confirm the code’s current descriptor, but any dollar figure for S0170 is payer-specific and subject to annual change.

Codes commonly confused with HCPCS Code S0170

Two alternatives are regularly confused with S0170 when billing anastrozole: J8999 and NDC-only billing. Picking the wrong one, or sending S0170 to a payer that does not accept S-series codes, produces a denial that requires resubmission.

When using J8999 as a fallback, include the drug name (anastrozole), the unit dose (1 mg), and the NDC in the claim narrative field. Without that detail, unlisted drug claims are usually denied for insufficient documentation. The other route is an NDC-only pharmacy claim, which some payers require for oral drugs.

The payer’s billing manual settles which route applies, and the PGM Billing HCPCS lookup tool confirms each code’s current descriptor. The diagram below maps each payer type to its claim route.

Why S0170 claims get denied and how to fix them

S0170 denials cluster around six causes, and most are preventable with eligibility checks and a documentation review before submission. Each denial arrives with claim denial codes that name the cause. A structured denial management process keeps the same error from recurring across patients.

Documentation requirements for clean S0170 claims

Clean documentation is cheaper to assemble before submission than after a denial, and it anchors medical billing compliance for oral chemotherapy. The checklist below covers what payers expect in the file behind an S0170 claim.

• Prescription with dispensed quantity and dose: confirms the 1 mg dosage and the number of tablets dispensed, from which units are calculated.
• Pathology report confirming HR+ receptor status: the primary clinical justification for anastrozole. Most PA submissions and some payer audits require this on file.
• Prior authorization approval number and expiration date: if PA was required. Practices billing long-term hormonal therapy should track renewal dates so no fill goes out under an expired approval.
• 11-digit NDC in N4 format with unit qualifier: required by most Medicaid programs and many commercial payers. A missing NDC is a frequent administrative denial on S0170 claims.
• Prescriber NPI: for the ordering oncologist or prescribing physician. Some payers verify prescriber specialty for oncology drugs.
• ICD-10-CM diagnosis code linked to anastrozole’s indication: must align with the clinical record. Do not use an unspecified C50 code when laterality and site are documented in the chart.

A superbill that captures these data points at dispensing means nobody has to dig for them when a denial arrives. Practices dispensing anastrozole regularly should build an S0170 checklist into the dispensing workflow, rather than relying on billing staff to catch missing fields after submission.

How claims management software keeps S0170 claims clean

An S0170 claim usually fails on a field someone typed twice: the unit count, the NDC, or the PA number. Billing staff copy those values from the prescription into a separate billing tool, then chase the payer by phone when a claim stalls.

Pabau submits claims electronically from the patient record and tracks each claim’s status after it goes out. Your team enters the units, NDC and PA number once, and the claim carries the data already in the record.

The payoff is less manual re-entry and one place to see which S0170 claims are paid, pending or denied. Staff spend their time fixing the few denials instead of hunting for them.

Submit and track S0170 claims in one place

Pabau’s claims management submits your S0170 claims and tracks each status, so billing staff spend less time re-keying claim data and chasing payers.

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Conclusion

Settle the payer route before you count a single unit. Medicare fills go to the pharmacy as Part D claims, and payers without S-codes need J8999 or an NDC-based pharmacy claim. Only the payers that accept S-series codes should ever see S0170.

Once the route is right, the remaining denials come from three fields: units, NDC and PA dates. A dispensing checklist catches the first two, and a renewal calendar protects a course of therapy that runs five years or more.

Pabau’s claims management submits S0170 claims and tracks every status, so your team re-keys less and spots denials sooner. Book a demo to see how it fits your oral drug billing workflow.

Continue your research

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Want to understand how drug billing fits into broader revenue cycle processes? What is revenue cycle management explains the end-to-end claims workflow from eligibility verification to payment posting.

Looking for guidance on keeping drug billing documentation clean? Submitting a clean claim walks through the fields and documentation standards that prevent administrative denials before claims reach the payer.

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