In this environment of ever changing treatment modalities available to cancer patients, I think it will be helpful to review the below Coding Guideline:
Patient admission/encounter solely for administration of chemotherapy, immunotherapy and radiation therapy
If a patient admission/encounter is solely for the administration of chemotherapy, immunotherapy or external beam radiation therapy assign code Z51.0, Encounter for antineoplastic radiation therapy, or Z51.11, Encounter for antineoplastic chemotherapy, or Z51.12, Encounter for antineoplastic immunotherapy as the first-listed or principal diagnosis. If a patient receives more than one of these therapies during the same admission more than one of these codes may be assigned, in any sequence.
This guideline is really important to remember, particularly if patients are being admitted for multiple types of treatment.
For example, if a patient is admitted for both chemotherapy and radiation therapy either Z51.11 or Z51.0 may be sequenced as the principal diagnosis if documentation supports they both meet the definition of a principal diagnosis. A word of caution: the selection of principal diagnosis between these two Z codes will affect your MS-DRG assignment!
Similarly, a patient may receive immunotherapy and chemotherapy during the admission and either may be selected as your principal diagnosis if both meet the definition of principal diagnosis. In this case, the MS-DRG will be the same.
Keep this Official Coding Guideline in mind when you are coding patients who are admitted to the hospital for cancer treatments. It will help you determine the most appropriate principal diagnosis for your patient population.