Byrne, Clare

e17035 Background: 177 Lu-PSMA-617 was approved in March 2022 for patients with mCRPC pretreated with an androgen receptor pathway inhibitor (ARPI) and a taxane. There are limited data on the effectiveness of treatments post- 177 Lu-PSMA-617. The aim of this study was to describe prostate-specific antigen (PSA) responses among patients with mCRPC receiving a guideline-recommended therapy as the next therapy after 177 Lu-PSMA-617 treatment. Methods: This retrospective, observational study used real-world data from the PRECISION data platform, a proprietary dataset developed by Novartis, comprised of patient-level electronic health record and claims data that represent the US advanced prostate cancer population in the community, academic, urology, and medical oncology settings. Patients with mCRPC who received any guideline-recommended therapy at least 14 days after treatment with 177 Lu-PSMA-617 between March 23, 2022 and July 31, 2024 were included. Guideline-recommended therapies included abiraterone, enzalutamide, darolutamide, apalutamide, cabazitaxel, docetaxel, pembrolizumab, sipuleucel-T, niraparib, olaparib, talazoparib, rucaparib, and radium-223. Patients’ PSA values while on 177 Lu-PSMA-617 treatment were compared with their PSA values during the subsequent therapy course. Proportions of patients achieving reductions in PSA levels ≥50% (PSA50) and ≥80% (PSA80) were estimated. All analyses were descriptive. Results: A total of 152 patients receiving any subsequent guideline-recommended therapy after 177 Lu-PSMA-617 were identified. Mean age was 72.1 years. Most patients received an ARPI (n=93, 61.2%) – abiraterone (n=38), enzalutamide (n=37), darolutamide (n=10), or apalutamide (n=8) – as their subsequent therapy. Of patients who received a taxane (n=42, 27.6%), 24 received cabazitaxel and 18 received docetaxel. Median time to initiation of subsequent therapy was 206 days (interquartile range [IQR] 101–301 days) from 177 Lu-PSMA-617 initiation and 44 days (IQR 17–119 days) from 177 Lu-PSMA-617 discontinuation. Overall, among patients with sufficient information for PSA evaluation (n=30), 46.7% achieved PSA50 and 40.0% PSA80 post- 177 Lu-PSMA-617. Among patients receiving an ARPI, PSA50 was observed in 11/18 (61.1%) and PSA80 in 10/18 (55.6%). Among patients receiving a taxane, PSA50 and PSA80 were seen in 3/12 (25.0%) and 2/12 (16.7%), respectively. Conclusions: In this real-world analysis, the majority of patients who received guideline-recommended therapies after 177 Lu-PSMA-617 achieved at least a PSA50 response, suggesting that 177 Lu-PSMA-617 treatment does not preclude response to other subsequent therapies.

e17030 Background: The broad therapeutic arsenal for mCRPC, with overlapping indications, makes selecting the optimal treatment sequence challenging in clinical practice. The aim of this study was to evaluate the prostate-specific antigen (PSA) responses and overall survival (OS) among patients with mCRPC receiving 177 Lu-PSMA-617 based on prior ARPI and taxane treatment exposure. Methods: This retrospective, observational study used real-world data from the PRECISION data platform, a harmonized dataset of advanced prostate cancer patients in the US from diverse clinical settings. Patients with mCRPC who had received ≥1 dose of 177 Lu-PSMA-617 between March 23, 2022 and July 31, 2024, after prior treatment with ≥1 ARPI and ≥1 taxane, were included. To assess PSA response, the baseline PSA value obtained within 90 days before starting 177 Lu-PSMA-617 was compared with the on-treatment PSA value obtained ≥28 days after 177 Lu-PSMA-617 initiation. The number of patients achieving PSA reductions ≥50% (PSA50) and ≥80% (PSA80) were estimated, with patients classified into two cohorts based on prior ARPI and taxane exposure: (1) prompt cohort: after only 1 ARPI and 1 taxane, and (2) deferred cohort: >1 ARPI and/or >1 taxane. Patient characteristics and treatment patterns were evaluated descriptively. OS from 177 Lu-PSMA-617 initiation was estimated using Kaplan–Meier methodology. Results: A total of 431 patients were included: 177 patients in the prompt cohort and 254 patients in the deferred cohort. Of patients in the deferred cohort, 185 (72.8%) received ≥1 ARPI and 1 taxane, 32 (12.6%) received 1 ARPI and ≥1 taxane, and 37 (14.6%) received ≥1 ARPI and ≥1 taxane. Median (interquartile range) age was 73 (67–78) years and most demographic characteristics were balanced between groups. Patients in the deferred cohort had higher median PSA levels at baseline (63.1 ng/mL vs 25.2 ng/mL). PSA50 was observed in 18/33 (55%) patients in the prompt cohort vs 28/66 (42%) in the deferred cohort. PSA80 was observed in 13/33 (39%) patients in the prompt cohort vs 21/66 (31%) in the deferred cohort. Across both cohorts, median OS was 18.0 months (95% confidence interval [CI]: 15.1 months–not reached [NR]). Median OS was NR in patients in the prompt cohort vs 15.1 months in patients in the deferred cohort (95% CI: 11.6 months–NR). Conclusions: In this large real-world study, prompt initiation of 177 Lu-PSMA-617 (after only 1 ARPI and 1 taxane) showed superior clinical outcomes versus deferred initiation of 177 Lu-PSMA-617. Patients were more likely to achieve a PSA reduction ≥50% and ≥80% and had longer OS with prompt initiation of 177 Lu-PSMA-617. These results may help to guide treatment sequencing in clinical practice.

61 Background: 177 Lu-PSMA-617 was approved in March 2022 for patients with mCRPC pretreated with an androgen receptor pathway inhibitor (ARPI) and a taxane. There are limited data on the effectiveness of treatments post- 177 Lu-PSMA-617. The aim of this study was to describe prostate-specific antigen (PSA) responses among patients with mCRPC receiving a guideline-recommended therapy as the next therapy after 177 Lu-PSMA-617 treatment. Methods: This retrospective, observational study used real-world data from the PRECISION data platform, a proprietary dataset developed by Novartis, comprised of patient-level electronic health record and claims data that represent the US advanced prostate cancer population in the community, academic, urology, and medical oncology settings. Patients with mCRPC who received any guideline-recommended therapy at least 14 days after treatment with 177 Lu-PSMA-617 between March 23, 2022 and July 31, 2024 were included. Guideline-recommended therapies included abiraterone, enzalutamide, darolutamide, apalutamide, cabazitaxel, docetaxel, pembrolizumab, sipuleucel-T, niraparib, olaparib, talazoparib, rucaparib, and radium-223. Patients’ PSA values while on 177 Lu-PSMA-617 treatment were compared with their PSA values during the subsequent therapy course. Proportions of patients achieving reductions in PSA levels ≥50% (PSA50) and ≥80% (PSA80) were estimated. All analyses were descriptive. Results: A total of 152 patients receiving any subsequent guideline-recommended therapy after 177 Lu-PSMA-617 were identified. Mean age was 72.1 years. Most patients received an ARPI (n=93, 61.2%) – abiraterone (n=38), enzalutamide (n=37), darolutamide (n=10), or apalutamide (n=8) – as their subsequent therapy. Of patients who received a taxane (n=42, 27.6%), 24 received cabazitaxel and 18 received docetaxel. Median time to initiation of subsequent therapy was 206 days (interquartile range [IQR] 101–301 days) from 177 Lu-PSMA-617 initiation and 44 days (IQR 17–119 days) from 177 Lu-PSMA-617 discontinuation. Overall, among patients with sufficient information for PSA evaluation (n=30), 46.7% achieved PSA50 and 40.0% PSA80 post- 177 Lu-PSMA-617. Among patients receiving an ARPI, PSA50 was observed in 11/18 (61.1%) and PSA80 in 10/18 (55.6%). Among patients receiving a taxane, PSA50 and PSA80 were seen in 3/12 (25.0%) and 2/12 (16.7%), respectively. Conclusions: In this real-world analysis, the majority of patients who received guideline-recommended therapies after 177 Lu-PSMA-617 achieved at least a PSA50 response, suggesting that 177 Lu-PSMA-617 treatment does not preclude response to other subsequent therapies.

56 Background: The broad therapeutic arsenal for mCRPC, with overlapping indications, makes selecting the optimal treatment sequence challenging in clinical practice. The aim of this study was to evaluate the prostate-specific antigen (PSA) responses and overall survival (OS) among patients with mCRPC receiving 177 Lu-PSMA-617 based on prior ARPI and taxane treatment exposure. Methods: This retrospective, observational study used real-world data from the PRECISION data platform, a harmonized dataset of advanced prostate cancer patients in the US from diverse clinical settings. Patients with mCRPC who had received ≥1 dose of 177 Lu-PSMA-617 between March 23, 2022 and July 31, 2024, after prior treatment with ≥1 ARPI and ≥1 taxane, were included. To assess PSA response, the baseline PSA value obtained within 90 days before starting 177 Lu-PSMA-617 was compared with the on-treatment PSA value obtained ≥28 days after 177 Lu-PSMA-617 initiation. The number of patients achieving PSA reductions ≥50% (PSA50) and ≥80% (PSA80) were estimated, with patients classified into two cohorts based on prior ARPI and taxane exposure: (1) prompt cohort: after only 1 ARPI and 1 taxane, and (2) deferred cohort: >1 ARPI and/or >1 taxane. Patient characteristics and treatment patterns were evaluated descriptively. OS from 177 Lu-PSMA-617 initiation was estimated using Kaplan–Meier methodology. Results: A total of 431 patients were included: 177 patients in the prompt cohort and 254 patients in the deferred cohort. Of patients in the deferred cohort, 185 (72.8%) received ≥1 ARPI and 1 taxane, 32 (12.6%) received 1 ARPI and ≥1 taxane, and 37 (14.6%) received ≥1 ARPI and ≥1 taxane. Median (interquartile range age was 73 (67–78) years and most demographic characteristics were balanced between groups. Patients in the deferred cohort had higher median PSA levels at baseline (63.1 ng/mL vs 25.2 ng/mL). PSA50 was observed in 18/33 (55%) patients in the prompt cohort vs 28/66 (42%) in the deferred cohort. PSA80 was observed in 13/33 (39%) patients in the prompt cohort vs 21/66 (31%) in the deferred cohort. Across both cohorts, median OS was 18.0 months (95% confidence interval [CI]: 15.1 months–not reached [NR]). Median OS was NR in patients in the prompt cohort vs 15.1 months in patients in the deferred cohort (95% CI: 11.6 months–NR). Conclusions: In this large real-world study, prompt initiation of 177 Lu-PSMA-617 (after only 1 ARPI and 1 taxane) showed superior clinical outcomes versus deferred initiation of 177 Lu-PSMA-617. Patients were more likely to achieve a PSA reduction ≥50% and ≥80% and had longer OS with prompt initiation of 177 Lu-PSMA-617. These results may help to guide treatment sequencing in clinical practice.