Background: Recent advances and approvals in mCSPC treatment offer improved outcomes. Docetaxel chemotherapy as well as novel hormonal therapies (NHT) including abiraterone, apalutamide and enzalumide are preferred regimens in addition to androgen deprivation therapy (ADT), with category 1 evidence supporting their use. Despite lack of consensus regarding use of first-generation anti-androgens (fgAI) aside from tumor flare prevention, they are still frequently prescribed. This multitude of options may lead to disparities in prescribing patterns. Methods: Retrospective analysis of pharmacy and medical claims data from the IQVIA database was performed. Patients were aged >18 years and had an ICD 9/10 diagnosis of metastatic prostate cancer (PCa) with >1 treatment claim. Patients on active therapy for another primary malignancy as well as those with <12 months of data pre- and <9 months post-first PCa-related event were excluded. Data was collected from 1/1/2015 to 6/30/2020. Treatment categories were classified as NHT, fgAI, chemotherapy, or ADT monotherapy. Results: National (N) and state of California (S) prescribing patterns are provided in Table. Nationally, Medicare reimbursed 16% NHT, 30% fgAI, 2% chemotherapy and 52% ADT, while third-party payers reimbursed 18% NHT, 20% fgAI, 3% chemotherapy and 59% ADT in 2020. State of California 2020 data yielded similar reimbursement patterns. In Southern California, academic centers prescribed 31% NHT, 23% fgAI and 46% ADT, while community-based practices prescribed 7% NHT, 36% fgAI and 57% ADT in 2020. In Southern California, community oncology practices prescribed 12% NHT, 40% fgAI, 2% chemotherapy and 44% ADT, while community urology practices prescribed 2% NHT, 38% fgAI, and 59% ADT in 2020. Data from 2015-2019 was similar. Conclusions: Although NHT utilization is increasing while chemotherapy utilization is declining, only a minority of mCSPC men received these therapies in 2020. Most of mCSPC men still receive ADT monotherapy or fgAI. Type of insurance carrier does not appear to affect prescribing patterns. Dramatic variations across treatment settings and different specialties exist, with academic centers prescribing more NHT than community-based practices and oncology practices prescribing more NHT than urology practices. These disparities should be addressed with provider education to standardize care delivery for mCSPC patients.