Lehner, Kelly

e17168 Background: Prostate cancer is the most prevalent cancer and the second leading cancer related death in men in the USA. Radical prostatectomy represents the mainstay treatment for patients with localized prostate cancer. Management of metastatic disease requires multidisciplinary practice and innovative approach for individualized favorable outcomes. Treatment sequencing in patients with advanced prostate cancer has been reported to impact patient’s response to subsequent treatment as well as overall survival outcomes. Here in, we thought to investigate the impact of prior chemotherapy treatment on PSA response rates to 177Lut PSMA. Methods: We conduct a single center retrospective study including 164 patients diagnosed with advanced prostate cancer and treated with 177Lut PSMA for metastatic hormone resistant prostate cancer. 92 patients received 177Lut PSMA as a salvage treatment late after chemotherapy (group A), and we compared them with 70 patients received 177Lut PSMA early in an adjuvant fashion within 3 months after chemotherapy (group B). Favorable PSA response was defined by 50% or more reduction in PSA value after complete treatment with 177Lut PSMA. Results: Approximately 43 % of patients in (group B) received their 177Lut PSMA within six months. The average number of chemo cycles received by patients of (group B) is between 3 to 6 cycles. Median patients’ age (IQR) 63 years (57.75 - 68), median (IQR) number of cycles of 177Lut PSMA 5 (5 - 6). Statistical analyses were performed to determine any differences in post lut PSA response in both groups of patients. Approximately 49 % of patients in (group A) had favorable PSA response versus 44 % of patients in (group B) (p-value 0.3853). Conclusions: The use of 177Lut-PSMA in the post-chemotherapy setting demonstrated similar outcomes whether administered early or late. These findings suggest that the timing of treatment may not significantly impact its effectiveness, but further research is needed to confirm these results and explore potential optimizations for patient care.

e17081 Background: Prostate cancer is the most common cancer in men. In early localized disease, surgery represents the mainstay treatment. However, management of metastatic and advanced stages requires multidisciplinary approach. The prognosis in metastatic prostate cancer has improved recently due to advanced pharmaceutical and interventional methods of treatment with modern diagnostic methods. In our study, we aim to investigate the impact of concomitant treatment with 2nd generation hormonal therapy and 177Lut PSMA on PSA response in patients with metastatic CRPC Methods: In a retrospective observation study including 91male patients with metastatic CRPC treated with 177Lut PSMA, we divided our cohort into 2 groups depending on whether they had 2nd generation hormonal therapy alongside their treatment with 177Lut PSMA. 43 patients received 177Lut PSMA (group A). While the other 48 patients (group B) had 2 nd generation hormone therapy with 177Lut PSMA. Primary endpoint was PSA response after they complete their therapy. Favorable PSA response was defined by PSA reduction more than 50% from baseline PSA before treatment Results: Statistical analysis identified 91 male patients, median (IQR) age of 61.5 years (56,67.75). Median (IQR) Gleason score 8 (7 - 9). Pre-177Lut PSMA PSA had a median of 2 (0.255 - 99), post-177Lut PSMA had a median of 0.15 (0.1 - 2.7). Median (IQR) 177Lut PSMA 6 (5 - 6). There was no significant change in PSA response in patients who received 177Lut PSMA alone versus 177Lut PSMA with concomitant 2 nd generation hormonal therapy. Of that, 54.17% of group B had favorable PSA response compared to 48.84% of group A (P value 0.6115). In multivariable analysis, concomitant treatment with 2nd generation hormone therapy and 177Lut PSMA has no impact on PSA response rates. Conclusions: This data suggests that concomitant treatment with 2nd generation therapy and 177Lut PSMA did not demonstrate superior PSA response than treatment with 177Lut PSMA alone. This data contributes to the current literature and serve in patients counseling. Further studies are warranted.

192 Background: In the setting of disease progression of metastatic castrate resistant prostate cancer (mCRPC) on docetaxel, abiraterone acetate (AA) and enzalutamide are two commonly used second line therapies with data demonstrating survival benefits. Less is known about patient specific factors that contribute to success with these therapies. The objective of this study is to improve patient selection for post-docetaxel second generation hormone therapy (AA or enzalutamide) by evaluating whether overall metastatic burden is associated with treatment response in this setting. Methods: By retrospective chart review, patients with mCRPC treated with AA or enzalutamide following docetaxel failure (defined as PSA rise and radiographic progression) were identified. Patients were categorized into low volume and high volume metastatic disease based on the number of pre-treatment metastatic lesions; where low volume disease describes patients with ≤ 5 metastatic lesions (e.g. oligometastatic disease), and high volume disease represents patients with > 5 individual lesions. The primary endpoint was cancer-specific mortality and the secondary endpoint was radiographic progression free survival. Median follow-up time was 29.5 months. Results: 75 patients were identified and included in our analysis: 39 with high volume metastatic disease, and 36 with low volume metastatic disease. Baseline characteristics of age and pre-treatment ECOG were not statistically different between these groups. Pre-treatment high-volume disease burden was significantly associated with increased risk of radiographic disease progression (HR 4.21, 95%CI 1.97-8.99, p < 0.0001) and cancer specific mortality (HR 5.84, 95% CI 1.58-21.53, p = 0.0026) during treatment with second generation androgen deprivation therapy. Conclusions: High volume metastatic disease burden is associated with significantly increased cancer specific mortality and decreased progression free survival for patients on second line therapy with AA or enzalutamide following docetaxel treatment failure.

189 Background: The objective of this study is to evaluate the prognostic value of early PSA decline following initiation of second-generation hormone therapy (2nd HT), namely abiraterone acetate or enzalutamide, in the post-chemotherapy setting in patients with metastatic castrate-resistant prostate cancer (mCRPC). Methods: We retrospectively identified 75 m-CRPC patients treated with 2nd HT following docetaxel failure (defined as PSA rise and radiographic progression). Patients were categorized into two groups based on first PSA within 3 months after initiation of therapy: PSA reduction ≥ 50% (Group A) and PSA reduction < 50% (Group B). The primary endpoint was cancer-specific mortality and the secondary endpoint was radiographic progression free survival. Results: There were 75 patients (52 in group A, 23 in group B) in the analytic cohort. Baseline clinical and demographic characteristics, including median age, primary Gleason score risk group, median pre-treatment PSA, disease burden, site of metastases, and pre-treatment ECOG score were not statistically different between the two groups. PSA reduction ≥50% was significantly associated with decreased risk of radiographic disease progression (HR 0.41, 95%CI 0.21-0.80, p = 0.0113) as well as decreased risk of cancer-specific mortality (HR 0.29, 95%CI 0.09-0.87, p = 0.0325). Conclusions: PSA reduction ≥50% within 3 months of starting 2nd HT for patients with mCRPC who have failed first-line docetaxel is associated with significantly improved 3-year cancer-specific mortality and progression free survival. Our data supports the use of PSA as an early prognosticating marker for patient outcomes on this second line therapy. [Table: see text]