I disagree - refer to the ICD-10 guidelines for Chapter 2, see below. Treatment directed at a malignancy should be coded with the primary malignancy diagnosis even if the malignancy has been excised.
In this example, Z51.12 could be the more appropriate principal diagnosis, with the bladder cancer secondary:
If the treatment is directed at the malignancy, designate the malignancy as the principal diagnosis.
The only exception to this guideline is if a patient admission/encounter is solely for the administration of chemotherapy, immunotherapy or external beam radiation therapy, assign the appropriate Z51.-- code as the first-listed or principal diagnosis, and the diagnosis or problem for which the service is being performed as a secondary diagnosis....
When a primary malignancy has been excised but further treatment, such as an additional surgery for the malignancy, radiation therapy or chemotherapy is directed to that site, the primary malignancy code should be used until treatment is completed.
When a primary malignancy has been previously excised or eradicated from its site, there is no further treatment (of the malignancy) directed to that site, and there is no evidence of any existing primary malignancy at that site, a code from category Z85, Personal history of malignant neoplasm, should be used to indicate the former site of the malignancy.
