At our hospital, anti-cancer drug administration is managed using a regimen-ordering system, and orders for the outpatient department and hospital wards have to be placed by 15:00 and 14:00 the day before they are required. On the day of treatment, the doctor examines the patient, confirms the test results, and places the final order for treatment on the patient's electronic medical record. In response, the pharmacist adjusts the anti-cancer drug preparation, and treatment is provided in the outpatient setting or in a ward. Although drug costs have increased due to the widespread use of immunotherapy, there have been cases where a drug was wasted after the required amount was adjusted on the day of treatment or drugs were discarded altogether, which pose serious problems. From April 2016 to March 2021, the total number of cases of drug wastage following placement of the final treatment order and drug disposal were 146 and 84, respectively, and the total associated economic loss was 5.81 million yen. The main causes were pre-confirmation mistakes and patients' physical condition on the day of treatment; some cancellations caused by patient-related factors were unavoidable. The current status of drug disposal is reported to the hospital director every 6 months, and the doctor-in-charge is interviewed regarding the reason for the wastage. In cases involving the disposal of large quantities of drugs(≥100,000 yen), the department manager and medical office manager are contacted, and an incident report is submitted. In 2021, drugs worth 2.03 million yen were discarded between April and September, which is worth serious consideration. It is essential to understand the reasons for drug wastage, pay attention to expensive regimens, and take appropriate measures at each facility.