Ostrowski, Micah

This cohort study examines patterns of bone-modifying agent use from 2013 to 2024 among men with metastatic castration-resistant prostate cancer.

ImportancePatients with metastatic castration–resistant prostate cancer (mCRPC) harboring BRCA1/2 alterations are eligible to receive poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors as single agents or in combination with an androgen receptor pathway inhibitor after these agents showed survival improvement in their landmark clinical trials. However, data are limited regarding the uptake of PARP inhibitors in these patients.ObjectiveTo investigate the use of PARP inhibitors in patients with mCRPC harboring BRCA1/2 alterations.Design, Setting, and ParticipantsThis retrospective cohort study used the deidentified Flatiron-Health electronic health record–derived database of US community and academic practices to extract patient-level data. The data cutoff date was May 31, 2024. Patients with mCRPC with evidence of harboring BRCA1/2 alterations and alive after August 15, 2020 (ie, 3 months after the approval of the first PARP inhibitor, rucaparib, in mCRPC) were included. Statistical analysis was performed from September 2024 to May 2025.ExposuresAge, race and ethnicity, insurance status, and practice type at the time of mCRPC diagnosis.Main Outcomes and MeasuresThe receipt of PARP inhibitors. Multivariable logistic regression was conducted to assess the association between the exposures and the main outcome.ResultsOf 24 105 patients with metastatic prostate cancer, 443 male patients (median [IQR] age, 72 [65-79] years) had mCRPC with BRCA1/2 alterations and were eligible and included in our analysis. Of these patients, 227 (51.2%) received a PARP inhibitor, whereas 216 (48.8%) did not. Compared with patients covered by a commercial health plan, those covered by Medicare were significantly more likely to receive a PARP inhibitor (odds ratio, 1.91; 95% CI, 1.02-3.66; P = .047). The odds of receiving a PARP inhibitor were not significantly higher in patients treated in community practice compared with those treated in academic centers (odds ratio, 1.64; 95% CI, 1.00-2.70; P = .05).Conclusions and RelevanceThis retrospective cohort study of patients with mCRPC and evidence of BRCA1/2 alterations found that approximately half of patients did not receive PARP inhibitors despite evidence of survival improvement in this population. These findings highlight the need to increase awareness of the survival data and access to life-prolonging therapies in patients with mCRPC.

5076 Background: C and Lu are both life-prolonging therapies for pts with mCRPC after progression on androgen receptor pathway inhibitor (ARPI) and docetaxel (D). Herein, our objective was to assess the comparative effectiveness of C vs. Lu in pts with mCRPC with prior progression on D and ARPI in real-world pts in the USA. Methods: A de-identified nationwide Flatiron Health electronic health record (EHR)-derived database was used to extract pt-level data. Eligibility: pts with mCRPC who progressed on D and ARPI and received for the first-time single-agent C or Lu. Pts who received alternative Lu or C in a later line of therapy (LOT) were excluded. Endpoints: real-world time to next therapy (rwTTNT) and real-world overall survival (rwOS). These were summarized via Kaplan-Meier survival estimates with a 95% confidence interval (CI) and compared in the context of propensity score (PS) matching weighted analysis using the Cox proportional hazard model. PS model included the following covariates: age, race-ethnicity, socioeconomic status, treatment year, Gleason score, ECOG performance status, log2PSA, alkaline phosphatase, hemoglobin, creatinine, LOT, insurance, and practice type. All the covariates achieved balance after PS matching weighting. Results: Among 24,105 pts with metastatic prostate cancer in the dataset, 1,445 met the eligibility criteria and were included (1,227 treated with C, 218 treated with Lu). In C cohort: median age was 73 (IQR 67 – 78), 66.9% had Gleason score ≥ 8, and median LOT was 4 (IQR 3-4). In Lu cohort: median age was 75 (IQR 67.25 – 80), 68.1% had Gleason score ≥ 8, and median LOT was 4 (IQR 3-5). In PS matching weighting analysis, there was evidence that pts receiving Lu had a significantly improved rwTTNT (median 8.3 months [mo], 95% CI 6.3 – 9.8) compared to those receiving C (median 4.7 mo, 95% CI 4.2 – 5.4) (HR 0.49, 95% CI 0.37 – 0.63, p < 0.001), which persisted after adjusting for covariates (HR 0.43, 95% CI 0.32 – 0.57, p < 0.001). Additionally, there was evidence that rwOS was longer in pts receiving Lu (median 10.3, 95% CI 8.9 – 12.8) compared to those receiving C (median 8.8 mo, 95% CI 6.6 – 10.8) (HR 0.69, 95% CI 0.51 – 0.92, p = 0.01). This improvement in rwOS with Lu compared to C persisted after adjusting for covariates (HR 0.61, 95% CI 0.44 – 0.84, p < 0.001). Conclusions: This is the largest real-world data to date assessing the comparative effectiveness of Lu vs. C, and it showed significantly longer rwTTNT and rwOS with Lu compared to C in pts with mCRPC pretreated with ARPI and D. Limitations: retrospective nature, selection bias, missingness, lack of randomization, etc. and residual confounding in real-world datasets. Upon external validation, these findings could guide treatment selection in the clinic and design of clinical trials.

108 Background: PARPi are approved for the treatment of pts with mCRPC either as single agents or as a combination with an androgen receptor pathway inhibitor (ARPI) [PMID: 37442702]. In a US Food and Drug Administration (FDA) pooled analysis, the benefit from PARPi appeared greatest for pts harboring BRCA1/2 alterations [PMID: 38484203]. However, real-world uptake of PARPi in pts with mCRPC with BRCA1/2 alterations is unknown. Herein, our objective was to assess the usage of PARPi in real-world pts with mCRPC harboring BRCA1/2 alterations. Methods: A de-identified nationwide Flatiron Health electronic health record (EHR)-derived database was used to extract pt-level data. Eligibility criteria: pts with mCRPC harboring alterations in BRCA1 or BRCA2 or both and alive after 8/15/2020 (i.e., 3 months following the approval of the first PARPi, rucaparib, in mCRPC) with available treatment information. The data cutoff date was 5/31/2024. Pts were categorized into two cohorts based on the receipt of any PARPi or not. Baseline characteristics at the time of mCRPC diagnosis, including age, race-ethnicity, and insurance plan, were collected in both cohorts. Results: Of the overall cohort of 24,105 pts with metastatic prostate cancer, 443 pts had mCRPC with BRCA1/2 alterations and were eligible and included in this analysis. 227 (51.2%) received a PARPi, while 216 did not (48.8%). Among the 227 pts who received a PARPi, 166 received it as a single agent (73.1%), 40 received it in combination with an ARPI (17.6%), and 21 received it in combination with other agents (9.3%). The median age was 72 in both cohorts (IQR 65 – 79 in patients receiving a PARPi and 66 – 78 in patients who did not). Other baseline characteristics in both groups are shown (Table). Conclusions: Despite PARPi demonstrating survival improvement in pts with mCRPC with BRCA1/2 alterations, a significant proportion of pts do not receive them. Our findings highlight the need to improve education among clinicians of level 1 evidence and improve access to life-prolonging therapies in pts with mCRPC. Baseline characteristics of pts with mCRPC who received vs. did not receive a PARPi. Characteristic Subgroup Pts who received a PARPiN = 227 Pts who did not receive a PARPiN = 216 Race-ethnicity, n (%) Asian 9 (4) 1 (0.5) Black 22 (9.7) 30 (13.9) Hispanic-Latino 10 (4.4) 10 (4.6) White 149 (65.6) 124 (57.4) Other and unknown 37 (16.3) 51 (23.6) Insurance, n (%) Commercial health plan 192 (84.5) 182 (84.3) Medicare-other government programs 31 (13.7) 18 (8.3) Medicaid 1 (0.4) 3 (1.4) Others and unknown 3 (1.3) 13 (6)

75 Background: The Rx landscape of pts with mCRPC has recently evolved with the approval of lutetium-177-PSMA-617 (Lu-177) and poly(ADP) ribose polymerase inhibitors (PARPi) either as single agents or as combinations with an androgen receptor pathway inhibitor (ARPI) [PMID: 37442702]. However, real-world data on the uptake of these agents are lacking. Herein, we sought to assess the Rx patterns and attrition rates of pts with mCRPC in the era of newly approved therapies. Methods: The de-identified nationwide Flatiron Health Electronic-Health Record (EHR)-derived database was used to extract pt-level data. Eligibility criteria: diagnosis of mCRPC and Rx line (L) information. The data cut-off date was 5/31/2024. Rx patterns in each line of therapies were summarized using frequency and percentages. All analysis was done using R version 4.2.3. Results: Of the overall cohort of 24,105 pts with metastatic prostate cancer, 12,333 pts diagnosed with mCRPC between 1/1/2013 and 5/9/2024 met the eligibility criteria and were included. Rx trends are summarized (Table). Of pts receiving 1L Rx, 61% of pts received 2L therapy, and 35% received 3L therapy. Androgen receptor pathway inhibitor (ARPI) was the most common Rx in the 1L setting (73.7%), followed by taxane (10%) and sipuleucel-T (3.8%). In 2L, ARPI was again the most frequent Rx (46.8%), followed by taxane (23.6%). In 3L, taxane became the most frequent Rx (35.4%), followed by ARPI (26.2%) and radium-223 (4.9%). Rx trends per year will be presented in the meeting. Conclusions: In the current era,a high proportion of pts with mCRPC receiving 1L Rx do not receive a subsequent line of Rx (39% of pts do not receive 2L, and 65% do not receive 3L Rx). ARPIs and taxanes remain the most frequently used Rx options in most L of therapy. These findings highlight the need for better tolerated Rx, therapies with a novel mechanism of action, and improved access to care for our pts. Rx trends per year will be presented in the meeting. Rx patterns in pts with mCRPC. Rx 1L, n (%)N = 12,333 2L, n (%)N = 7475 3L, n (%)N = 4316 4L, n (%)N = 2339 5L, n (%)N = 1225 ARPI 9085 (73.7) 3503 (46.8) 1130 (26.2) 356 (15.2) 157 (12.8) PARPi-based therapies 93 (0.8) 185 (2.5) 142 (3.3) 98 (4.2) 47 (3.9) Platinum-based therapy 127 (1) 216 (2.9) 198 (4.6) 148 (6.3) 130 (10.6) Lu-177-based therapies 50 (0.4) 109 (1.5) 169 (3.9) 143 (6.3) 103 (8.4) Radium-223 183 (1.5) 241 (3.2) 213 (4.9) 125 (5.3) 79 (6.4) Sipuleucel-T 474 (3.8) 94 (1.3) 53 (1.2) 18 (0.8) 8 (0.7) Taxane 1240 (10) 1763 (23.6) 1526 (35.4) 935 (40) 393 (32) Pembrolizumab 24 (0.2) 41 (0.5) 36 (0.8) 27 (1.2) 29 (2.4) Other*/not-applicable** 665 (5.4)/392 (3.2) 1000 (13.4)/323 (4.3) 602 (14)/247 (5.7) 320 (13.7)/169 (7.2) 162 (13.3)/117 (9.5) *Includes drugs approved for mCRPC in combination with unapproved agents or clinical trial drugs. **Includes agents not approved for prostate cancer.

95 Background: Most pts with prostate cancer with bone metastasis experience symptomatic skeletal events (SSEs) [PMID: 23884473], leading to increased morbidity and mortality. BMAs have been approved since 2007 and are recommended in mCRPC to prevent SSEs in pts with bone metastases or a high risk of osteoporotic fracture. Herein, we sought to assess the real-world trends of BMA administration in pts with mCRPC. Methods: We used the de-identified nationwide Flatiron Health electronic health record (EHR)-derived database to extract pt-level data. Inclusion criteria: pts with mCRPC with available date of diagnosis of mCRPC and information on receipt of BMA. Pts were categorized into 2 cohorts based on BMA receipt (e.g., bisphosphonates, denosumab, teriparatide, romosozumab) or not. Treatment trends of BMA by year of mCRPC diagnosis were summarized using frequency and percentages. Baseline characteristics at the time of mCRPC diagnosis (age, race-ethnicity, practice type, insurance) were compared between cohorts using the Wilcoxon rank-sum and Chi-squared tests. Results: Of 24,105 pts with metastatic prostate cancer in the dataset, 14,112 with mCRPC were eligible and included. 7,990 (56.6%) received BMA while 6,122 (43.4%) did not. In BMA receipt cohort: median age was 75 (IQR 67 – 81), majority were White (61%), treated in community practice (87%) and had commercial health plan (80%). In BMA non receipt cohort: median age was 75 (IQR 68 – 82), majority were White (61%), treated in a community practice (78%), and had commercial health plan (76%). The use of BMA decreased over time from 56% in 2013 to 46% in 2024 (Table). Statistically significant differences existed between cohorts in race-ethnicity, practice type, and insurance (p < 0.001) and will be presented at the meeting. Conclusions: Despite recommendations to use BMAs in pts with mCRPC and bone metastasis or high risk of osteoporotic fracture, our findings reveal a low utilization rate of BMAs in mCRPC setting with a notable decline over time. This highlights the need to incorporate the use of BMAs in clinical practice and improve access to these agents. Trends by year of mCRPC diagnosis in receipt of the first BMA and frequency and percentage of each agent. Year 2013N = 549 2014N = 1035 2015N = 1223 2016N = 1345 2017N = 1441 2018N = 1346 2019N = 1469 2020N = 1380 2021N = 1352 2022N = 1393 2023N = 1196 2024N = 383 Receipt of BMA, n (%) 316 (56) 674 (65) 792 (65) 837 (62) 886 (61) 766 (57) 816 (56) 766 (56) 692 (51) 713 (51) 556 (46) 176 (46) Denosumab, n (%) 190 (60.1) 450 (66.8) 557 (70.3) 599 (71.6) 606 (68.4) 533 (70) 526 (64.5) 488 (63.7) 410 (59.2) 414 (58.1) 290 (52.2) 94 (53) Zoledronic acid, n (%) 120 (38) 220 (32.6) 228 (28.7) 233 (27.8) 270 (30.5) 225 (29) 281 (34.4) 273 (35.6) 277 (40) 295 (41.4) 258 (46.4) 82 (47) Teriparatide, other bisphosphonates, n (%) 6 (1.9) 4 (0.6) 7 (1) 5 (0.6) 10 (1.1) 8 (1) 9 (1.1) 5 (0.7) 5 (0.7) 4 (0.5) 8 (1.4) 0

90 Background: Poly(ADP) ribose polymerase inhibitors and pembrolizumab are approved for patients with metastatic prostate cancer (mPC) with susceptible genomic alterations based on NGS testing. We recently reported that the rate of NGS testing in mPC remains low at 29.3% in the United States (1). Herein, we investigated the rates of NGS testing at the end of life in a real-world patient population. Methods: This study utilized the nationwide Flatiron Health electronic health record (EHR)-derived de-identified database. Eligibility: diagnosis of mPC, with information on receipt of NGS testing (blood/tissue) and recorded date of death. The time between each patient’s first NGS testing result date and date of death was measured and categorized into 3 groups: NGS test results delivered more than 3 months (mo) before death, within 3 mo of death, and delivered after death. Frequencies and percentages of these 3 categories were reported, also by the year of death. Results: Out of 24,105 patients with mPC in the database, 3,397 had both a recorded date of death and underwent NGS testing and were eligible and included. The median age was 74 (IQR 67–80), 70% were White non-Hispanic, and 83% were treated in a community-based practice. In these patients, 2,901 (85.4%) NGS results were reported more than 3 mo before death, 457 (13.5%) within 3 mo of death, and 39 (1.1%) after death. From 2015 to 2024, the percentage of patients receiving their result more than 3 mo before death increased from 27% to 91%, while those receiving it within 3 mo before death decreased from 55% to 8.5%, and the percentage of NGS results reported after death declined from 18% to 0.6%. Baseline characteristics (including race-ethnicity, insurance plan, practice type [academic vs. community]) in these categories will be presented at the meeting. Conclusions: Despite the availability of life-prolonging targeted therapies based on NGS testing results for patients with mPC, in ∼14% of patients, the first NGS testing results were reported within 3 mo before death or after death. The lack of timely NGS testing limits patients' access to life-prolonging personalized treatments in earlier settings, resulting in missed opportunities for improved outcomes. 1. Hage Chehade, Swami, JAMA Network Open, 2024.

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)