e18687 Background: The long-acting injectable G-CSF, pegfilgrastim and its biosimilars have historically been given to patients 24 hours following the administration of myelosuppressive chemotherapy for either primary or secondary prophylaxis of febrile neutropenia (FN). Previous literature has indicated that pegfilgrastim administration prior to 24 hours post chemotherapy, may result in a deepened and prolonged neutropenia due to the increase in circulating granulocytes exposed to chemotherapy. With the onset of the COVID-19 pandemic and to reduce potential SAR-CoV-2 exposure to cancer patients on therapy, we implemented same day administration of injectable pegfilgrastim-cbqv among select breast cancer patients receiving myelosuppressive chemotherapy regimens from March 2020 – February 2021. Methods: Utilizing retrospective EHR chart reviews, 55 patients among 4 medical oncologists in our breast cancer group were identified as meeting the criteria of same day pegfilgrastim-cbqv administration. Inclusion was based on completion of at least 2 consecutive cycles of same day pegfilgrastim-cbqv 6 mg subcutaneous injection for primary or secondary prophylaxis. The selected patient charts were reviewed for the incidence and severity of FN. Among the patients who had documented FN, further subgroup analyses were done regarding baseline characteristics, timing of neutropenia, regimens, regimen sequence, and reported ADRs associated with pegfilgrastim-cbqv. Results: 9 (16.4%) of the 55 patients experienced FN (Grades 3-4) and 6 (10.9%) patients were hospitalized. There were no Grade 5 events and none had therapy discontinued due to FN. 8 (88.9%) of the patients experienced FN between cycles 1 and 2. Of note, there were no cases of COVID-19 among the 9 patients who had an episode of FN. 52 (94.5%) of the 55 patients received treatment with curative intent and 3 (5.5%) had metastatic disease on a subsequent line of therapy. The median age was 49.1 years (range 29-71) and patients were 56.4% Caucasian, 18.1% Black or African American, 12.7% Asian, and 12.7% Hispanic/Latina. Conclusions: Based on the retrospective data analysis, same day pegfilgrastim-cbqv appears to be a safe and effective option in the primary and secondary prophylaxis of FN with myelosuppressive standard of care chemotherapy used in breast cancer treatment. Though our review was limited by a relatively small sample size and confined to younger (49.1 median age) breast cancer patients, this opens the door to further re-evaluation of same day pegfilgrastim-cbqv administration in other patient populations. In a post pandemic treatment world, this slight change in practice has the potential to reduce patient financial toxicity associated with multiple medical visits, provide an alternative to on-body injector formulations, and ensure treatment adherence.
PO86 PREDICTIVE MARKERS OF CLINICAL OUTCOME FOR BREAST CANCER PATIENTS TREATED IN PHASE 1 TRIALS: NATIONAL CANCER CENTER HOSPITAL EXPERIENCE