Abstract PS5-03-20: Impact of granulocyte-colony stimulating factor use on clinical outcomes in metastatic breast cancer patients receiving chemotherapy

Abstract Background: The mainstay of triple negative breast cancer (TNBC) continues to be cytotoxic treatment, specifically carboplatin/gemcitabine, carboplatin/paclitaxel or sacituzumab govitecan. The most common adverse effect of these regimens is dose-dependent and dose-limiting neutropenia. Recent meta-analyses of randomized controlled trials (RCTs) have shown a reduction in all-cause mortality in patients receiving prophylactic G-CSF with cytotoxic chemotherapy as well as an association with improved overall survival (OS). However, these meta-analyses did not exclusively look at metastatic breast cancer patients. To the authors knowledge, this is the first real-world evidence study looking at G-CSF use in metastatic triple negative breast cancer. This study investigated the use of prophylactic G-CSF agents to determine if metastatic breast cancer patients receiving intermediate or high-risk chemotherapy regimens remained on treatment longer, resulting in less febrile neutropenia and better outcomes. Methods: In this retrospective, single center study we examined pts with early-stage breast cancer who received and discontinued denosumab or zoledronic acid. IRB approval was obtained. Number and length of treatments, fractures of any kind, and delay in BMA were collected from the electronic medical record using diagnosis codes. The objectives of this study were to describe the rate and severity of neutropenia, febrile neutropenia, progression-free survival (PFS) metastatic TNBC who received carboplatin/gemcitabine, carboplatin/paclitaxel or nab-paclitaxel, and sacituzumab govitecan. Results: A total of 197 patients were included with 79 receiving carboplatin plus gemcitabine, 20 receiving carboplatin plus paclitaxel or nab-paclitaxel, and 98 receiving Sacituzumab govitecan. The primary reason for exclusion was having not received the chemotherapy regimen despite having the treatment plan ordered. The median PFS was 4.9 months (95 % confidence interval [CI], 3.5 - 6.3) in the G-CSF group compared to 2.5 months in the no G-CSF group (95% CI, 2.2 - 3.2). PFS was significantly longer in the G-CSF group than in the no-G-CSF group (hazard ratio for disease progression or death, 0.66; 95% CI, 0.453 - 0.951; p = 0.026). The percentage of patients who were alive and free from progression at 12 months was 26.8% and 20.5% at 24 months. The incidence of febrile neutropenia was higher in the G-CSF group than in the no-G-CSF group (18 and 4 incidences, respectively; p = 0.012). However, when comparing patients who received primary prophylaxis and secondary prophylaxis, those receiving primary prophylaxis had a lower incidence of febrile neutropenia (4 and 14, respectively; p = 0.009). Conclusions: In this study, we found that PFS significantly improved in patients who received G-CSF at any point during their course of the treatment, with carboplatin plus gemcitabine, carboplatin plus paclitaxel or nab-paclitaxel, or Sacituzumab govitecan and patients receiving primary prophylaxis had a lower incidence of febrile neutropenia, treatment plan adjustment, and treatment discontinuation. Citation Format: M. Hofherr. Impact of granulocyte-colony stimulating factor use on clinical outcomes in metastatic breast cancer patients receiving chemotherapy [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-03-20.