Gebrael, Georges

104 Background: Androgen deprivation therapy (ADT) intensification [ADT + androgen receptor-pathway inhibitor (ARPIs) +/- docetaxel] has been shown to improve survival outcomes in pts with mHSPC and is recommended as standard of care by all major guidelines. However, prior studies have shown underutilization of ADT intensification [PMID: 39191549]. There are limited updated and large-scale studies on the use of ADT intensification, beyond January 2023. In this study, we aimed to assess the treatment patterns of ADT intensification in real-world pts with mHSPC in the US, including data on those treated since January 2023. Methods: This retrospective study utilized the nationwide Flatiron Health Electronic Health Record (EHR) derived de-identified database. Eligibility: Pts diagnosed with mHSPC and availability of treatment information (ADT and/or line of therapy in mHSPC). The data cut-off date was 5/31/2024. Treatment patterns were summarized using frequency and percentages. All analysis was done using R version 4.2.3. Results: Among 24,105 pts with metastatic prostate cancer in the database, a total of 14,084 were eligible and included. The median age at metastatic diagnosis was 72 years (IQR 65 – 79), and 60% were White non-Hispanic. In the overall cohort (1/1/2013–5/15/2024), 56.8% received ADT monotherapy, and 37.7% received ADT intensification. Table summarizes the treatment patterns by year, highlightinga consistent increase in adoption of intensified ADT regimens, and a decline in use of ADT monotherapy. Notably, since January 2023, 76.8% pts with mHSPC received ADT intensification while only 17.3% of pts received ADT monotherapy. Conclusions: To our knowledge, this is the first and largest study to evaluate the current use of ADT intensification. These data indicate a notable improvement in the adoption of level 1 evidence (ADT intensification) in the treatment of pts with mHSPC. These encouraging data emphasize the benefits of continued efforts to promote guideline-concordant care and provide the current treatment landscape to design clinical trials. Treatment patterns by year in pts with mHSPC. Treatment 2013–2017n = 5,263(%) 2018n = 1,313 (%) 2019n = 1,407(%) 2020n = 1,353(%) 2021n = 1,483(%) 2022n = 1,556(%) 2023n = 1,459(%) 2024n = 250(%) ADT monotherapy 4,095 (77.8) 856 (65.2) 819 (58.2) 664 (49) 698 (47.1) 569 (36.6) 291 (20) 5 (2) ADT + ARPI 155 (2.9) 238 (18) 354 (25.1) 452 (33) 555 (37.4) 695 (44.7) 842 (58) 154 (61.6) ADT + Docetaxel 709 (13.5) 156 (12) 175 (12.4) 156 (12) 134 (9.0) 117 (7.5) 78 (5.3) 19 (7.6) Triplet(ADT + ARPI + Docetaxel) 6 (0.1) 2 (0.2) 1 (0.1) 2 (0.1) 9 (0.6) 82 (5.2) 166 (11.1) 53 (21.2) Other therapies 298 (5.7) 61 (4.6) 58 (4.1) 79 (5.8) 87 (5.9) 93 (6) 82 (5.6) 19 (7.6)

212 Background: Patients with prostate cancer with liver metastases are known to have a worse prognosis. In this study, we evaluated ctDNA in mCRPC (metastatic castration-resistant prostate cancer) patients with and without liver metastases. Methods: A retrospective chart review identified mCRPC patients with liver metastases at Tulane Cancer Center and Huntsman Cancer Institute. Liver metastases were confirmed via molecular or conventional imaging. All patients had ctDNA assessed with a multi-gene cancer panel via the Guardant 360 assay. Alterations with <0.1% allelic fraction, synonymous alterations, and variants of unknown significance were excluded from analyses. Statistical analyses were performed using Fisher’s Exact and Wilcoxon Rank Sum Tests. Correction for multiple testing was not performed, hence these alterations may be subject to a type 1 error. Results: 53 mCRPC patients with liver metastases and 144 mCRPC patients without liver metastases were included in the study. We found seven genes that are more likely to be pathologically altered in ctDNA in mCRPC patients with liver metastases (See Tables 1-3): AR (OR=2.38, 95% CI: [1.25, 4.52], p=0.01), BRAF (OR=2.74, 95% CI:[1.05, 7.18], p=0.05), BRCA2 (OR=5.33, 95% CI:[1.49, 19.02], p=0.01), CDK6 (OR=4.09, 95% CI:[1.35, 12.42], p=0.01), EGFR (OR=3.12, 95% CI:[1.22, 7.99], p=0.02), FGFR1 (OR=5.69, 95% CI:[1.81, 17.86], p-value=0.003), MYC (OR=4.55, 95% CI:[1.63, 12.68], p=0.004), and PIK3CA (OR=4.34, 95% CI:[1.87, 10.06], p=0.01). Additionally, mCRPC patients with liver metastases are more likely to have copy number alterations (CNA) (p= 0.01) compared to mCRPC patients without liver involvement. There were no other significant differences in the remaining 70 genes interrogated. Germline pathogenic alterations did not vary between the two groups. Conclusions: In mCRPC patients with liver metastases, these exploratory analyses suggest ctDNA testing is more likely to detect pathologic alterations in AR, BRAF, BRCA2, CDK6, EGFR, FGFR1, MYC, and PIK3CA. Additionally, mCRPC patients were more likely to have copy number alterations (CNA). Limitations of the Guardant 360 assays are notable in this setting given the incomplete ascertainment of gene deletions and the incomplete number of prostate-relevant genes assessed. [Table: see text]