Oncology & Hematology Coding Alert

Question: AAPC’s 2023 ICD-10-CM Expert “Appendix A: Z Codes for Long-term Use of Drugs” lists irinotecan as Z79.634 and Z79.64 and oxaliplatin as Z79.64 and Z79.630.

Is the double code listing for each drug a typo? Or if not a typo, is there a way to tell which code to use when reading the medical notes?

AAPC Forum Participant

Answer: On Oct. 1, 2022, ICD-10-CM introduced a new code group under the Z79 (Long term (current) drug therapy) category. The group, Z79.6.- (Long term (current) use of immunomodulators and immunosuppressants), enables you to document long-term chemotherapy drug use according to the function of the drug.

Among the new codes introduced in that group was Z79.634 (Long term (current) use of topoisomerase inhibitor), which lists irinotecan as an inclusion term. ICD-10-CM lists irinotecan this way because, like similar drugs, it disrupts the cancer cells’ ability to multiply by blocking the topoisomerase enzyme in the body’s DNA.

Similarly, ICD-10-CM also provides a subcategory for chemotherapy drugs that function as alkylating agents, meaning they disrupt cancer cell growth by damaging DNA. This is how oxaliplatin works, and though it is not listed as an inclusion term for Z79.630 (Long term (current) use of alkylating agent), you would use that code for long-term use.

However, both drugs are also myelosuppressive agents, meaning they enable a decrease in production of red blood cells, white blood cells, and platelets. This is why Appendix A in AAPC’s ICD-10-CM Expert code book provides a second listing of Z79.64 (Long term (current) use of myelosuppressive agent) for both irinotecan and oxaliplatin. You can use Z79.64 simultaneously with other long-term use of chemotherapy codes to indicate that the drug is a myelosuppressive agent, but you can also use it independently if the patient is being treated for low blood cell count because of their chemotherapy medication.

However, the disclaimer that accompanies the appendix in AAPC’s edition of the ICD-10-CM code book tells you to “check with individual payers to determine their billing, coding, and reimbursement guidelines” when documenting a patient’s long-term chemotherapy drug use. So, your payer may want you to use one or two codes for irinotecan and oxaliplatin, or they may even want you to use different codes or code combinations to document their long-term use. This applies not only to irinotecan, oxaliplatin, and all the other sample drugs listed in Appendix A, but also to all the other drugs that are not listed in a list that is admittedly “comprehensive, but not exhaustive” per the opening disclaimer.