198P Complications associated with prolonged GCSF with dose-dense EC chemotherapy for early breast cancer patients

Background: Primary granulocyte-colony stimulating factor (GSCF) prophylaxis with dose-dense chemotherapy for early stage breast cancer is routine practice to prevent febrile neutropenia (FN). Our current practice administers 7 days of GCSF, which reduces the FN risk but is associated with extra toxicity and costs. We reviewed the rates of FN, neutropenia, hospital admissions and GCSF-related toxicity in early stage breast cancer patients receiving 7 days of GCSF with dose-dense epirubicin and cyclophosphamide (EC). Methods: Between 2018 and 2021, patients treated for early stage breast cancer with dose-dense epirubicin (90mg/m2) and cyclophosphamide (600mg/m2) given every 2 weeks at two London hospitals were identified from chemotherapy prescribing records. Treatment delays, dose reductions, hospital admissions and GCSF-related toxicity were assessed from medical records. Results: Ninety-seven patients were identified, receiving 373 cycles of dose-dense EC. Median age was 46 years (25 – 60 yrs). GCSF was prescribed for 7 days (days 3-10) at 300mcg and 480mcg for 82 and 15 patients respectively according to baseline weight. Three patients had dose delays due to neutropenia, one of whom was non-compliant with GCSF. Risk of hospital admission for any reason was 5.2% per patient (1.3% /cycle). Two patients were admitted with neutropenic sepsis (risk 2.1%/patient, 0.5%/cycle). One was admitted on day 7 and the other on day 10 of the cycle. Both had a neutrophil count of 0.26 x 10ˆ9 /L. One subsequently died of COVID pneumonitis. Toxicity to GCSF was recorded in 41% of patients (16.4%/cycle). Musculoskeletal pain was the most common toxicity (95%), others included headache and injection site pain. Thirty-three patients had neutrophilia (> 7.5 x 10ˆ9/L) prior to a cycle (event rate 17.4%/cycle). Duration of GCSF was reduced in 16 patients;12 due to toxicity, 1 due to neutrophilia, 1 due to raised neutrophil precursors and 2 not recorded. Of these, no patients had any further treatment delays or dose reductions. Conclusions: The optimal duration of GCSF prophylaxis to reduce the FN risk with dose-dense regimens is unclear. Seven days of GCSF is associated with toxicity - a reduction to 5 days should be considered. Legal entity responsible for the study: Royal Free London NHS Foundation Trust. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.