TPS272 Background: Treatment of metastatic castration-resistant prostate cancer (mCRPC) has been steadily evolving during the last decade, but access remains a significant issue in low- and middle-income countries (LMICs). As novel therapies emerge and translate into clinical practice, the gap in treatment patterns between patients who do or do not have access to these therapies is expected to increase. The resulting disparities in outcomes are likely to be more noticeable in countries with pronounced inequality, such as Brazil. In Brazil, while a minority of patients have private insurance and have access to nearly all available treatment options, approximately 75% of patients depend on the public health system, which is unable to afford most of the recent treatment innovations for mCRPC, such as novel hormonal agents (NHA) or PARP inhibitors. LACOG 1818 was developed to investigate and compare outcomes of patients with mCRPC treated at private and public hospitals in Brazil. Methods: LACOG 1818 (NCT04962919) is a retrospective multicentric study investigating disparities in cancer treatment and survival among public and private institutions in Brazil. Patients with mCRPC diagnosed within January 2014 and December 2017 will be included and their data will be abstracted from medical records. Primary endpoint is cause-specific survival, comparing patients from private and public institutions. We estimate that 299 events are needed to detect a hazard ratio of 0.75 indicating a lower risk of prostate cancer-related death for patients treated at private institutions with a power of 80% and a bicaudate significance level of 10%. Considering a follow up of 24 months and a median cause-specific survival of 20 months in patients from public institutions, 590 patients are planned to be included. Secondary endpoints include describing comorbidities, sociodemographic and clinicopathological characteristics of patients with mCRPC; comparing overall survival of patients with mCRPC treated at public and private institutions; comparing treatments patterns of patients with mCRPC treated at public and private institutions; and describing skeleton-related complications, bone-directed treatments, and admission rates. From January 2020 to August 2022, 244 of planned 590 patients have been enrolled in 7 Brazilian centers. Additional 12 centers are still planned to open before 2023. Results are expected in the first semester of 2023. Clinical trial information: NCT04962919 .