e17056 Background: Testicular germ cell tumors (GCTs) represent only one percent of all solid tumors; however, they are the most common solid malignancy in men 15-35 years old. Febrile neutropenia (FN) is a grievous complication of chemotherapy, frequently occurring in GCT patients. The aim of this retrospective study was to assess the effect of primary granulocyte-colony stimulating factor (G-CSF) prophylaxis on the incidence of FN in GCT patients. Methods: This study was conducted using the National Cancer Institute medical records database. Patients diagnosed with germ cell tumors treated with first line/adjuvant chemotherapy at the National Cancer Institute, Bratislava, Slovakia from January 2000 to December 2017 were eligible. Starting in January 2006, patients received G-CSF prophylaxis after every cycle of chemotherapy. Results: Out of 393 patients, 265 patients received primary G-CSF prophylaxis and 128 patients did not receive prophylaxis. The majority of patients (69.97%) were treated with bleomycin, etoposide and cisplatin chemotherapy. There were 61 deaths (15.5%) in our study population. 2- and 5-year OS of the study group was 86.8% and 83.1%, respectively. During the study period, 71 patients (18.1%) suffered FN events. Out of 128 patients who did not receive primary prophylaxis, 42 (32.8%) patients suffered FN, while only 29 (10.9%) patients with primary prophylaxis suffered FN ( P = 0.0000001). On subgroup analysis, FN incidence decreased in all groups with primary prophylaxis, except for patients with stage I GCT receiving adjuvant chemotherapy. Patients receiving G-CSF prophylaxis had significantly longer overall survival when compared to patients without prophylaxis. (HR = 0.44, 95% CI 0.26-0.75; P = 0.0009). Conclusions: Primary G-CSF prophylaxis was associated with significantly decreased FN incidence and longer overall survival in patients treated with first line chemotherapy and should be consider in all patients except stage I disease.