Introduction
Insurance denials continue to pose a serious obstacle for oncology practices, disrupting cash flow, creating administrative burdens, and delaying care for patients who need it most. With the rising costs of chemotherapy, specialty drugs, and frequent imaging, accurate billing is more critical than ever. Oncology also faces some of the toughest challenges in prior authorizations and coding due to complex treatment plans and rapidly changing protocols.
Denial rates in oncology often range from 15% to 20%, higher than in many other fields. For high-volume cancer centers, this can translate to millions in lost revenue each year. One industry report estimates that an average oncology practice loses $3 to $4 million annually, with over 60% of those denials being avoidable.In this post, we’ll break down the top 10 denial codes most commonly affecting oncology billing, explore the reasons behind them, and share actionable steps to help practices reduce denials and protect their revenue.
Common Denial Codes in Oncology
| Denial Code | Description |
|---|---|
CO 50 | Not Medically Necessary Service |
CO 15 | Authorization required |
CO 16 | Missing/incomplete information |
CO 18 | Duplicate claim/service |
CO 29 | Time limit for filing expired |
CO 204 | Service not covered under patient’s benefit plan |
CO 97 | Service already adjudicated |
CO 167 | Diagnosis not covered |
CO 22 | Coordination of benefits |
CO 151 | Payment adjusted because the payer deems the information submitted does not support this level of service |
Detailed Analysis of Top 10 Denials
1. Denial Code: CO 50
Description: Medical Necessity Denials
Medical necessity denials occur when insurers determine that an oncology treatment doesn’t meet their clinical criteria. These denials often affect chemotherapy regimens, immunotherapy treatments, or specific dosing schedules that don’t align with the payer’s approved protocols or clinical standards.In oncology, these denials can be especially difficult because treatments are often tailored to individual patients based on the latest research, including off-label uses of medications.
As new treatment strategies emerge, payer policies may not keep up with the rapid pace of innovation. Additionally, oncology care is highly personalized, with decisions often based on factors like genetic markers, previous treatment outcomes, or other patient-specific considerations that may not be fully addressed in standardized guidelines.When documentation doesn’t clearly explain the rationale for a treatment or fails to reference up-to-date clinical evidence, these denials can become a significant barrier to care.
Prevention:
- Clearly document the clinical rationale for treatment selection, especially for off-label or novel therapy uses
- Reference specific NCCN guidelines, clinical trials, or peer-reviewed literature supporting treatment decisions
- Document detailed patient-specific factors influencing treatment selection (genetic markers, prior therapy response, comorbidities)
- Implement pre-treatment chart reviews to ensure documentation supports the planned therapy
- Train providers on thorough documentation of performance status, disease staging, and biomarker results
2. Denial Code: CO 15
Description: Authorization Required
Authorization denials occur when the necessary pre-approval for oncology services is not obtained before treatment is provided. This is especially common for services such as advanced imaging studies (like PET scans), radiation therapy, and high-cost medications, including immunotherapies and targeted therapies.
These denials are particularly challenging for cancer centers, as they often lead to complete non-payment for costly services. The authorization process in oncology is complicated by the time-sensitive nature of cancer care, the need for frequent treatment adjustments based on patient response or side effects, and the extensive documentation required to justify specific therapies. Furthermore, many insurers have their own oncology-specific benefit management programs with distinct authorization rules, adding another layer of complexity to the process.
Prevention:
- Implement a robust tracking system specifically for oncology treatment authorizations
- Develop dedicated protocols for urgent cases requiring expedited authorizations
- Train staff on the specific clinical documentation required for oncology authorizations
- Verify authorization status before administering cancer treatments or performing imaging
- Document all authorization numbers in both clinical and billing systems
- Create clear communication channels between clinicians and authorization specialists
3. Denial Code: CO 16
Description: Bundled Procedure Denials
These denials occur when claims are submitted with missing or incorrect information. In oncology, common issues include missing or inaccurate diagnosis codes (such as specific cancer stages or genetic details), failure to include required modifiers for chemotherapy or radiation treatments, or incomplete documentation for drug wastage associated with expensive partial-vial chemotherapy medications.
Oncology coding is particularly complex, with numerous modifiers and specific requirements for different treatment types, making these technical denials more frequent. Moreover, as cancer treatments evolve and new therapy codes are introduced, it becomes increasingly challenging to ensure claims are accurate and complete.
Prevention:
- Verify all required documentation is present before claim submission
- Develop procedure-specific documentation templates for common oncology services
- Document drug wastage properly for partial-vial usage of expensive oncology medications
- Create standardized documentation templates for chemotherapy administration and radiation delivery
- Conduct regular audits to identify patterns of incomplete information
4. Denial Code: CO 18
Description: Duplicate Claim/Service
Duplicate claim denials occur when the same oncology service is billed more than once. In oncology, these denials are common due to the complexity of cancer treatment, which often involves multiple providers, lengthy treatment regimens, and services delivered in different settings. Claims may also be flagged as duplicates if they are resubmitted after being denied for other reasons without being properly marked as corrected claims. Common situations include confusion between radiation therapy planning and delivery codes, hospital and physician billing for the same chemotherapy administration, or accidental rebilling of recurring treatments, such as weekly chemotherapy sessions.
Prevention:
- Create clear protocols for resubmitting denied claims versus submitting corrected claims
- Use appropriate modifiers to indicate distinct procedures performed during the same encounter
- Coordinate billing between hospital and physician groups to prevent overlapping claims
- Train staff to check claim status before resubmitting
- Utilize claim scrubbing software with duplicate detection capabilities
5. Denial Code: CO 29
Description: Time Limit for Filing Expired
Late filing denials occur when claims are submitted after the payer’s filing deadline has passed. These deadlines can vary widely, from 30 days to a year after the service date. For oncology practices, timely filing can be especially difficult due to the long duration of cancer treatments, which often involve complex regimens that span months or even years. Additionally, the high cost of many oncology services makes these denials particularly impactful. Common causes include delays in obtaining complete clinical documentation for complicated cases, challenges in coordinating billing between multiple providers involved in cancer care, or administrative delays when processing claims for expensive treatments that require extra verification.
Prevention:
- Establish a standard claim submission schedule (daily or weekly)
- Implement electronic claims submission for faster processing
- Develop a tracking system for claims approaching filing deadlines
- Prioritize high-dollar oncology claims for expedited processing
- Train staff on varied timely filing requirements by payer type
6. Denial Code: CO 204
Description: Service Not Covered Under Patient’s Benefit Plan
Non-covered service denials occur when an oncology service is excluded from the patient’s insurance benefits. In oncology, this typically applies to innovative therapies like CAR-T cell treatment, proton beam therapy, or specific targeted therapies that may not be included in standard insurance plans. Unlike medical necessity denials, these services are excluded regardless of clinical need. These denials are particularly challenging because they often involve cutting-edge treatments that may be the best or only option for patients with advanced or hard-to-treat cancers. Moreover, the high cost of these therapies places a significant financial burden on patients when coverage is denied.
Prevention:
- Verify specific coverage for planned oncology treatments during insurance verification
- Create a database of commonly excluded cancer treatments by payer and plan type
- Implement advance beneficiary notice (ABN) protocols for Medicare patients
- Develop similar financial responsibility forms for commercial payers
- Train financial counselors on oncology-specific benefit verification
7. Denial Code: CO 97
Description: Service Already Adjudicated
Bundling denials occur when an oncology service is considered part of another service that has already been reimbursed. In oncology, this often affects supportive services provided during chemotherapy, elements of radiation therapy treatment planning and delivery, or services included in the global surgical package for oncologic surgeries. Understanding the intricate bundling rules in cancer care is crucial for accurate reimbursement, particularly given the frequent use of comprehensive service codes. Common examples include billing separately for hydration services during chemotherapy, multiple simulation services in radiation therapy planning, or routine post-operative care after tumor resection surgeries.
Prevention:
- Stay current on NCCI (National Correct Coding Initiative) edits affecting oncology services
- Implement coding software that flags potential bundling issues before submission
- Create reference guides for commonly bundled oncology services
- Train providers and coders on proper use of modifiers to indicate separately billable services
- Conduct regular audits of oncology coding patterns
8. Denial Code: C0 167
Description: Diagnosis Not Covered
Non-covered diagnosis denials occur when a specific cancer diagnosis or condition is not included in the patient’s insurance plan for the treatment provided. In oncology, these denials often affect off-label drug use for rare cancers, experimental treatments for resistant tumors, or specific genetic cancer subtypes that are not part of FDA-approved indications. These denials can be especially challenging because cancer treatment often progresses faster than the formal approval process, and doctors may recommend treatments based on the latest research, even if official indications have not been established. Additionally, rare cancer types or unusual tumor presentations may lack standard treatment protocols covered by insurance.
Prevention:
- Verify diagnosis coverage for specific treatments during insurance verification
- Document detailed clinical justification for off-label treatment of specific cancer diagnoses
- Reference peer-reviewed literature or guidelines supporting treatment for specific diagnoses
- Consider peer-to-peer reviews to explain rationale for treatment of rare cancer types
- Implement pre-treatment verification processes for diagnoses likely to trigger review
9. Denial Code: C0 22
Description: Coordination of Benefits
Coordination of Benefits (COB) denials occur when there is confusion over which insurance is primary when a patient has multiple sources of coverage. In oncology, these denials are particularly common because many cancer patients have complex insurance situations. Patients may have Medicare with supplemental plans, employer insurance alongside disability coverage, or private insurance with secondary Medicaid due to the financial burden of cancer treatment. Additionally, some patients may have specialized cancer policies or clinical trial coverage in addition to their regular insurance. Given the high cost of cancer care, determining the correct primary and secondary coverage is crucial for proper reimbursement.
Prevention:
- Implement thorough insurance verification processes that identify all potential coverage sources
- Verify primary vs. secondary insurance status during financial clearance
- Document all insurance information clearly in the patient record
- Create dedicated processes for handling patients with multiple coverage sources
- Train front desk staff on COB rules for different scenarios
10. Denial Code: CO 151
Description: Level of Service Not Supported
These denials occur when the documentation doesn’t justify the level of service billed for oncology care. In cancer treatment, this is common with evaluation and management services during chemotherapy, complex treatment planning for radiation therapy, or the physician work required for managing complicated cancer cases. Claims may be denied if the documentation fails to show the complexity of medical decision-making, the time spent, or the risk management involved at the billed service level. Due to the inherently complex nature of cancer care, it’s essential but challenging to ensure that documentation accurately reflects the work involved in providing oncology services.
Prevention:
- Train providers on proper documentation of medical decision-making complexity in oncology
- Create time-tracking protocols for services billed based on time spent
- Implement documentation requirements that align with specific level of service criteria
- Conduct regular audits of service level selection and supporting documentation
- Provide education on the specific elements required to support each service level
Conclusion
For oncology practices, tackling the top denial reasons requires a comprehensive approach that includes thorough documentation, streamlined workflows, staff training, and leveraging technology. The high cost of cancer treatment makes managing denials crucial for financial stability. Key strategies include establishing strong front-end verification, implementing specialized coding and billing procedures, and maintaining detailed clinical documentation that clearly supports medical necessity. With oncology care evolving rapidly, staying updated on payer policies and treatment guidelines is essential.
Consider conducting a denial analysis specific to your practice to pinpoint the most impactful denial issues. This data helps prioritize improvements for greater impact. Denial prevention should be an ongoing effort, involving regular monitoring, staff education, and adjustments as payer policies and cancer treatment protocols change. By prioritizing denial management, oncology practices can shift resources from administrative tasks to patient care, improving both financial outcomes and the overall patient experience.