In the case of a terminated chemotherapy infusion due to patient reaction, your payer may prefer you to include an additional diagnosis code such as V64.1 (Surgical or other procedure not carried out because of contraindication) or E933.1 (Drugs, medicinal, and biological substances causing adverse effects in therapeutic use; antineoplastic and immunosuppressive drugs) to describe the circumstances of the service. Remember the encounter (V58.11, Encounter for antineoplastic chemotherapy) and neoplasm ICD-9 codes (such as 174.x, Malignant neoplasm of female breast ...), too.