Reducing Neutropenia Incidence by Changing the Date of Eflapegrastim Administration in Breast Cancer Patients Who Have Experienced Neutropenia After Chemotherapy

The use of pegfilgrastim, which has a long-lasting effect in the human body, after myelosuppressive chemotherapy for solid tumors, including breast cancer, and blood cancers has led to a decrease in the incidence of neutropenia, including febrile neutropenia, and a reduction in medical costs by shortening hospitalization periods related to side effects of chemotherapy. During the early stages of drug development, there was controversy over the timing of pegfilgrastim administration, and attempts were made to administer it at various times, from the day of chemotherapy to the day of neutropenia began. However, based on several studies, it is now known that patients who receive pegfilgrastim on the day of chemotherapy or after 4 days of chemotherapy have a higher incidence of febrile neutropenia. Therefore, administering pegfilgrastim on day 1-3 after chemotherapy is ideal, but in reality, it is often difficult for patients to visit the hospital multiple times after chemotherapy, so many patients are discharged after receiving pegfilgrastim on day 1. The FDA and National Comprehensive Cancer Network (NCCN) guidelines also recommend administration on day 1. It is known that patients who experience neutropenia after the first round of chemotherapy are more likely to experience it again in subsequent rounds. The investigators aimed to see whether changing the pegfilgrastim administration date from day 1 to day 3 starting from the second round of chemotherapy for patients who experienced neutropenia after receiving pegfilgrastim on day 1 of the first round can reduce the incidence of neutropenia.