Background: To mitigate the risks of chemotherapy associated neutropenia, during the COVID-19 pandemic, all genitourinary (GU) cancer patients treated with chemotherapy at the Princess Margaret Cancer Centre (PMCC) were offered primary prophylaxis with GCSF. We hypothesize that this reduced rates of febrile neutropenia, hospitalizations, healthcare costs and improved overall outcomes, compared to GU cancer patients treated with chemotherapy without GCSF in the 2 years prior to the pandemic. Methods: We performed a retrospective review of GU cancer patients, receiving curative or palliative intent chemotherapy, with or without primary GCSF prophylaxis between January 2018 and June 2022. GCSF was given either as a single dose or as consecutive doses post chemotherapy. Main outcomes were incidence of febrile neutropenia, hospitalization, health care expenditures as well as disease specific outcomes. Results: Overall, 248 patients with prostate cancer (44%), urothelial cancers (33%) germ cell (21%), and rare GU cancers (4%) were identified. Median age was 70 (range 19-91), 92% were male, 65% were ECOG 0/1. Treatment intent was neoadjuvant (13%), adjuvant (20%), or palliative (67%). Main regimens used were docetaxel, cabazitaxel, carboplatin, cisplatin/etoposide, gemcitabine/cisplatin and BEP. Median follow-up was 10.5 months (0.23-52.3 months). A total of 206/248 received primary GCSF prophylaxis. During chemotherapy, the median white blood cell levels were higher in the GCSF group compared to the non-GCSF group (14.1*10*9/L vs 2.90*10*9/L, p<0.0001); and neutropenia rates were markedly lower (2% vs. 93%, P=<0.0001). Hospital admission rates were significantly lower in G-CSF users compared to non-users (19% vs. 69%, P<0.0001). Symptomatic disease progression 13% was the leading cause of admission in the G-CSF group. Infectious causes such as UTI, pneumonia, COVID-19, and sepsis were seen in only 12% of the G-CSF group compared to 31% in the non-users. G-CSF was generally well tolerated with just 0.97% discontinuing G-CSF. Conclusions: During the COVID-19 pandemic, primary prophylactic G-CSF use in GU cancer patients, undergoing chemotherapy significantly lowered rates of both febrile neutropenia and hospitalizations and could be a cost-effective strategy in this patient population that warrants further study.