Background: Treatment options for mHSPC have continued to evolve. While androgen deprivation therapy (ADT) has been the backbone treatment, more recently early use of docetaxel and/or novel androgen receptor inhibitors (nARIs) has demonstrated improved clinical outcomes. This study assessed real-world treatment among mHSPC patients who received at least one line of therapy (LoT). Methods: A retrospective observational study utilizing de-identified health records from five Cancer Treatment Centers of America (CTCA) included patients with metastatic prostate cancer who were treated with ADT, docetaxel or nARIs at CTCA for 6+ months between 1/2015-3/2021. Treatment patterns were observed from first LoT to metastatic castration resistance, death, or lost-to-follow-up until 3/2022. LoT was defined as first to last date of active drug therapy, not including long-term hormone agonists. First LoT was defined as initial regimen with no new drugs added 30+ days after start date. Patient characteristics, proportion and duration of each LoT, and reasons for early discontinuation were gathered using structured data elements and chart abstraction. Results: The characteristics of the 523 patients in this study were as follows: mean (SD) age 62 (8) years, 60% white and 33% black, 53% with commercial insurance, 75% with ECOG 0-1, and 65% with bone metastasis at diagnosis. Median follow-up time was 2.9 years. The most common LoT 1 regimen was either ADT alone or ADT with first generation androgen receptor inhibitors (FGARI) (table below). 46% received a second and 15% received a third LoT. Mean (SD) duration of first and second active LoTs were 12 (11.8) and 10 (11.1) months, respectively. Among the 65% and 78% patients who discontinued therapy in LoT 1 and 2, respectively, the majority discontinued due to progression of disease (35% LoT 1 and 53% LoT 2) followed by patient choice (23% LoT 1 and 18% LoT 2). Conclusions: Despite recommendations from guidelines on early intensification of therapy in mHSPC, in this contemporary cohort we find that most patients received either ADT alone or ADT ± FGARI in LoT 1 while chemotherapy and nARIs were initiated predominantly in later lines. Most patients discontinued LoT 1 due to disease progression which may suggest undertreatment and need for improved outcomes. Further studies are needed to assess the factors associated with non-intensification of treatments.