Make sure you avoid these interpretation errors.

Oncology coding is a critical component of the healthcare revenue cycle. It demands a detailed understanding of medical terminology, coding systems, payer rules, and close collaboration with providers. As an oncology coder, you ensure accurate documentation and billing for diagnostic tests, procedures, drugs/biologicals, and radiation therapy — all of which impact reimbursement, compliance, and patient care continuity.

In this article, we’ll delve into the common coding challenges that you face as an oncology coder and offer some timely advice for you to overcome them.

Stay on Top of Frequent Coding Updates

You probably know that ICD-10-CM and CPT^® code sets update annually in October and January, respectively, and that HCPCS Level II updates quarterly. Changes include new codes, deletions, revisions, and revisions to instruction essential for accurate coding and compliance.

However, it is important to know that ICD-10-CM receives a small revision in April. Though this revision mostly corrects typographical errors from previous editions, the Centers for Disease Control and Prevention (CDC) can sometimes add new diagnosis codes and make minor guideline.changes in this revision. CPT^®, too, releases minor changes throughout the year, with the temporary category III emerging technology codes updating biannually, and category II performance measurement codes updating three times a year.

Do this: Frequently review official publications, attend webinars, read industry articles and other academic/professional resources, and monitor changes to coding software and payer websites.

Be Aware of Evolving Payer Policies and Regulations

The Centers for Medicare & Medicaid Services (CMS) issues annual regulatory updates through the CY Medicare Physician Fee Schedule (PFS) final rule, typically published in November, with many payers adopting changes at the start of the calendar year. However, policy updates, including new, revised, or retired guidance, can occur year-round and may be difficult to track due to fragmented communication and complex websites.

Do this: Stay informed by subscribing to payer listservs and newsletters, attending trainings, and regularly reviewing CMS national coverage determinations (NCDs), Medicare Administrative Contractors (MACs) local coverage determinations (LCDs), and LCD reference articles.

Avoid Misinterpretation and Misapplication Errors

As much as you try to be 100 percent accurate in your work, errors resulting from misinterpretation of complex guidelines, inconsistent payer rules, incomplete documentation, or lack of training can often creep in. Consequences include claim denials, audits, or legal exposure.

Here are some typical examples of problem areas for you to be aware of.

Evaluation and Management (E/M): Assigning the most appropriate E/M level for a patient encounter can be very tricky. For the complexity of problems addressed during the encounter element, for example, you cannot automatically assign a high level of complexity for a cancer diagnosis.

Do this: Documentation must support that the condition presents a “significant risk of morbidity or poses a threat to life or bodily function in the near term without treatment,” per CPT^® guidelines. Examples that may justify high complexity include severe side effects from treatment, a new diagnosis of extensive metastatic disease, or abrupt cognitive changes.

Similarly, you cannot automatically assign a high level of risk for cancer drug therapy in the risk of complications of patient management element without documentation of intensive monitoring.

Do this: To support a high-risk level, the provider must clearly document both the reason for the monitoring and the nature of the monitoring itself. For instance, the AMA provides the example of “monitoring for cytopenia in the use of an antineoplastic agent between dose cycles.”

ICD-10-CM: Here, misinterpreting guidelines can lead you to assign incorrect diagnosis codes. For example, you need to avoid coding a malignancy as active when the patient has a history of cancer, and vice versa.

Do this: If the primary malignancy has been successfully excised or eradicated, no further treatment is being administered, and there is no evidence of disease, assign a personal history of malignant neoplasm code (Z85.-), which documents routine surveillance for recurrence. A provider query may be necessary for clarification if documentation is unclear.

Diagnoses should be coded to the highest level of specificity. In oncology coding, that means accounting for laterality, tumor site, cancer type, stage, and presence of metastasis.

Do this: If documentation lacks specificity, a query to the provider is appropriate. Incomplete or ambiguous documentation can negatively impact reimbursement, risk adjustment, and quality reporting. You should also be very careful before assigning an uncertain behavior code. These codes should only be used when the pathologist explicitly states that the neoplasm’s behavior is uncertain — in other words, it cannot be definitively classified as benign or malignant.

Modifiers: Knowing when — and when not — to append a modifier to a claim line is a constant cause of confusion in oncology coding. Specifically, three modifiers are responsible for creating the majority of coding headaches in the specialty:

• Modifier 25 (Significant, separately identifiable evaluation and management service by the same physician or other qualified health care professional on the same day of the procedure or other service). Documentation must support that a significant, separately identifiable E/M service was performed by the same provider on the same day as another procedure or service. An example that may support modifier 25 would be a patient receiving chemotherapy who requires a separate evaluation due to new symptoms.

Do this: Coders should verify that the documentation meets the criteria for Modifier 25 and that it is appropriate based on code combinations (e.g., National Correct Coding Initiative [NCCI] edits).

• Modifiers JW (Drug amount discarded/not administered to any patient) and JZ (Zero drug amount discarded/not administered to any patient). Remember, JW is used to report drug waste and requires two claim lines (one for the administered amount and one for the discarded amount), while JZ is used when no drug waste occurs and is reported with one claim line.

Do this: Query providers when documentation regarding drug administration and waste is unclear.

Understand Units for Precise Reporting

Miscalculations or incomplete documentation can lead to over-/under-reporting units. Coders must ensure accuracy when calculating and reporting units.

Do this: If documentation is unclear, you should query the provider. Additionally, if you are experiencing challenges with unit calculations, seek training.

The Bottom Line

Oncology coding is complex, requiring you to continually adapt to evolving regulations, guidelines, and clinical documentation standards. By remaining proactive, using the right tools, and fostering collaboration with providers, you can navigate this challenging field with confidence — ensuring compliance, optimal reimbursement, and high-quality care.

Carrie Weiss, CPC, CEMC, LPN, Senior Manager, Pinnacle Enterprise Risk Consulting Services