Concurrent Androgen Deprivation Therapy Research Articles

Prostate-Specific Membrane Antigen PET/CT-Guided, Metastasis-Directed Radiotherapy for Oligometastatic Castration-Resistant Prostate Cancer.

Systemic treatments for metastatic castration-resistant prostate cancer (mCRPC) include androgen deprivation therapy, androgen receptor pathway inhibitors, chemotherapy, and radiopharmaceuticals, all of which have associated toxicity. Prostate-specific membrane antigen (PSMA) PET/CT allows for higher sensitivity in detecting metastatic disease than is possible with conventional imaging. We hypothesized that PSMA PET/CT-guided, metastasis-directed radiotherapy may offer durable disease control with low toxicity rates in patients with mCRPC who have a limited number of metastases. Methods: We retrospectively screened 5 prospective PSMA PET/CT studies for patients with mCRPC who had up to 5 sites of oligorecurrent or oligoprogressive disease on PSMA PET/CT and subsequently received definitive-intent, metastasis-directed radiotherapy to all new or progressing sites with concurrent androgen deprivation therapy. Progression-free survival, freedom from new lines of systemic therapy, and overall survival (OS) were calculated from the start of metastasis-directed radiotherapy using Kaplan-Meier analysis. Biochemical response was defined as at least a 50% decrease in prostate-specific antigen 6 mo after the start of treatment. Toxicity was graded using the Common Terminology Criteria for Adverse Events, version 5. Results: Twenty-four patients met the inclusion criteria with a median follow-up of 33.8 mo (interquartile range, 27.6-45.1 mo). Between October 2017 and April 2023, 11 patients (45.8%) had 1 treated site, 10 patients (41.7%) had 2, and 3 patients (12.5%) had 3. Five sites were prostate or prostate bed, 15 were nodal, 19 were osseous, and 1 was visceral. Seventeen patients (70.8%) continued their preexisting systemic therapy, whereas 7 (29.2%) started a new systemic therapy. Median progression-free survival was 16.4 mo (95% CI, 9.8-23.0 mo). The biochemical response rate was 66.7%. Median freedom from a new line of systemic therapy was 29.0 mo (95% CI, 7.6-50.4 mo). Median OS was not reached. The 2- and 4-y OS rates were 91.1% (95% CI, 79.3%-100%) and 68.8% (95% CI, 45.1%-92.5%), respectively. Grade 2 and grade 3 or higher toxicity rates were 4.2% and 0%, respectively. Conclusion: PSMA PET/CT-guided, metastasis-directed radiotherapy appears to offer durable disease control with low toxicity rates for oligometastatic castration-resistant prostate cancer. Further prospective studies are needed to compare metastasis-directed radiotherapy with systemic therapy versus systemic therapy alone and PSMA PET/CT-guided versus conventional imaging-guided radiotherapy.

Real-world evidence of 18F-fluciclovine Positron emission tomography/computed tomography performance for recurrent prostate cancer in the Veterans Affairs Health System.

There are no population-level studies assessing 18F-fluciclovine (fluciclovine) utilization of Positron emission tomography/computed tomography (PET/CT) for biochemically recurrent prostate cancer (PC). We assessed fluciclovine PET/CT in the Veterans Affairs Health Care System. Of 1153 men with claims suggesting receipt of fluciclovine PET/CT, we randomly reviewed charts of 300 who indeed underwent fluciclovine PET/CT. The primary outcome was fluciclovine PET/CT result (positive or negative). Comparison among groups stratified by androgen deprivation therapy (ADT) (yes vs. no) and prostate-specific antigen (PSA) (≤1 vs. >1 ng/mL) at imaging were performed. Logistic regression tested associations between PSA, ADT receipt, and race with fluciclovine PET/CT positive imaging. Fluciclovine PET/CT positivity rate was 33% for patients with PSA 0-0.5 ng/mL, 21% for >0.5-1.0, 54% for >1.0-2.0, and 66% for >2.0 (p < 0.01). A 59% positivity rate ocurred in patients treated with concurrent ADT versus 37% in those not on ADT (p < 0.01). White were more likely to have a positive scan versus Black patients (55% vs. 38%; p = 0.02). Patients whose primary treatment was radical prostatectomy had a lower positivity rate (33%) versus those treated with radiotherapy (55%) (p < 0.001). On multivariable logistic regression, PSA > 1 ng/mL (all men odds ratio [OR]: 4.06, 95% confidence interval [CI]: 2.07-7.96; men on ADT only OR: 4.42, 95% CI: 1.73-11.26) and use of ADT (OR: 3.94, 95% CI: 1.32-11.75), and White (all men OR: 2.22, 95% CI: 1.20-4.17) predicted positive fluciclovine PET/CT. This real-world study assessing 18F-fluciclovine PET/CT performance in an equal access health care system confirms higher detection rates than traditional imaging methods, but positivity is highly influenced by PSA at time of imaging. Additionally, patients currently receiving ADT have at least four times higher likelihood of a positive scan, showing that scan positivity isn't negatively affected by ADT status in this study. Finally, White men were more likely to have a positive scan, the reasons for which should be explored in future studies.

TRIUMPH: phase II trial of rucaparib monotherapy in patients with metastatic hormone-sensitive prostate cancer harboring germline homologous recombination repair gene mutations.

The activity of PARP inhibitors (PARPi) in patients with homologous recombination repair (HRR) mutations and metastatic castration-resistant prostate cancer has been established. We hypothesized that the benefit of PARPi can be maintained in the absence of androgen deprivation therapy (ADT) in an HRR-mutated population. We report the results of a phase II clinical trial of rucaparib monotherapy in patients with metastatic hormone-sensitive prostate cancer (mHSPC). This was a multi-center, single-arm phase II trial (NCT03413995) for patients with asymptomatic, mHSPC. Patients were required to have a pathogenic germline mutation in an HRR gene for eligibility. All patients received rucaparib 600mg by mouth twice daily, without androgen deprivation. The primary endpoint was a confirmed PSA50 response rate. Twelve patients were enrolled, 7 with a BRCA1/2 mutation and 5 with a CHEK2 mutation. The confirmed PSA50 response rate to rucaparib was 41.7% (N = 5/12, 95% CI: 15.2-72.3%, one-sided P = .81 against the 50% null), which did not meet the pre-specified efficacy boundary to enroll additional patients. In patients with measurable disease, the objective response rate was 60% (N = 3/5), all with a BRCA2 mutation. The median radiographic progression-free survival on rucaparib was estimated at 12.0 months (95% CI: 8.0-NR months). The majority of adverse events were grade ≤2, and expected. Rucaparib can induce clinical responses in a biomarker-selected metastatic prostate cancer population without concurrent ADT. However, the pre-specified efficacy threshold was not met, and enrolment was truncated. Although durable responses were observed in a subset of patients, further study of PARPi treatment without ADT in mHSPC is unlikely to change clinical practice.

Testosterone replacement therapy (TRT) in patients with locoregional prostate cancer (LPC) treated with prior androgen deprivation therapy (ADT): A single center review.

e24045 Background: In LPC, ADT may be combined with radiation therapy (RT) for 4-24 months. Post-ADT, a significant proportion of men experience prolonged hypogonadism. TRT can alleviate symptoms and improve metabolic outcomes. Contrary to longstanding concerns, there is no substantial evidence of increased prostate cancer recurrence in patients (pts) treated with single modalities (surgery or RT). However, sparse data ( &lt; 100 cases published to our knowledge) exist regarding recurrence risk of LPC with TRT after prior ADT, where baseline T levels may fall below the androgen receptor saturation point. Methods: We retrospectively abstracted clinical data from hospital records of men with stage I – IVA PC, treated with prior concurrent ADT and RT and subsequently received TRT between January 2014 and September 2023. Extracted data included demographics, cancer diagnosis/staging, ADT/TRT treatment details and PSA and clinical outcomes. The co-primary endpoints were change in PSA and incidence of PC recurrence. Results: 21 pts met criteria. Median age was 77. ISUP Grade Groups (GG) included: GG1: 2, GG2: 2, GG3: 8, GG4: 2, and GG5: 7. AJCC 8th ed. stages were: I: 2, II: 7, III: 7, IV-A: 5. The median duration of prior ADT was 8 months (IQR 5 – 17) and the median interval from RT to TRT was 19 months (IQR: 12 – 44). Prior to TRT, the median testosterone level was 30.5 ng/dL (IQR: 17-76). TRT formulations included: injection: 6, oral: 4, topical: 13. The median follow-up period from the start of TRT was 13 months, and the median duration on TRT was 10 months (IQR: 5-22). TRT was ongoing in 15 (71.4%) pts and discontinued in 6 (28.6%). Reasons for discontinuation included testosterone recovery (1), hospice (not PC related) (2), no perceived benefit (2), MD concern for PSA rise (1). After TRT, the median testosterone level was 336 ng/dL (IQR: 207-462). Median PSA pre- and post-TRT were undetectable and 0.08 ng/dL, respectively. None of the subjects experienced PC recurrence or PC-specific mortality. One pt showed PSA bounce without recurrence. Median BMI was unchanged before (28.3 kg/m2) and after (27.7 kg/m2) TRT (p = 0.48). Due to the nature of the study, quality of life measures and metabolic parameters could not be systematically abstracted. Conclusions: In men with LPC who remained hypogonadal long-term after prior ADT and RT, we found that TRT was not associated with a significant rise in median PSA and no cases of PC recurrence were documented. This included many with a history of very high-risk cancers (eg. GG ≥ 4, Stage ≥ III). This study adds to the sparse existing literature in this clinical setting and together they support the case for a prospective trial utilizing TRT in patients who remain hypogonadal after ADT and radiation.

Differences in real-world outcomes by risk classification for localized prostate cancer patients after radiation therapy.

Limited real-world evidence exists on the long-term clinical outcomes of patients with localized prostate cancer (LPC) who received external beam radiation therapy (EBRT) as the initial treatment. This study evaluated clinical outcomes of US patients with high-risk LPC (HR-LPC) and low/intermediate-risk LPC (LIR-LPC) who received EBRT. This retrospective study using Surveillance, Epidemiology, and End Results-Medicare linked data from 2012 to 2019 included patients ≥ 65 years old who received EBRT as initial therapy. Baseline patient characteristics were summarized, metastasis-free survival (MFS), overall survival, and time to initiation of advanced prostate cancer treatment were compared using Kaplan-Meier (KM) and adjusted Cox proportional hazard (PH) models. 5-year survival probabilities stratified by race/ethnicity (non-Hispanic [NH] White, NH Black, NH Asian, and Hispanic) were assessed. Of 11,313 eligible patients, 41% (n = 4600) had HR-LPC and 59% (n = 6713) had LIR-LPC. Patient characteristics for both groups were comparable, with mean age at EBRT initiation > 70 years, 86% white, and mean follow-up time >40 months. More patients in the HR-LPC than LIR-LPC groups (78% vs 34%) had concurrent androgen deprivation therapy use and for a longer duration (median 10.4 months vs. 7.4 months). A higher proportion of HR-LPC patients developed metastasis, died, or received advanced prostate cancer treatment. Adjusted Cox PH survival analyses showed significantly (p < 0.0001) higher risk of mortality (hazard ratios[HR], 1.57 [1.38, 2.34]), metastasis or death (HR, 1.97 [1.78, 2.17]), and advanced prostate cancer therapy use (HR, 2.57 [2.11, 3.14]) for HR-LPC than LIR-LPC patients. Within 5 years after the initial EBRT treatment, 18%-26% of patients with HR-LPC are expected to have died or developed metastasis. The 5-year MFS rate in the HR-LPC group was lower than the LIR-LPC group across all racial/ethnic subgroups. NH Black patients with HR-LPC had the highest all-cause mortality rate and lowest rate of receiving advanced prostate cancer treatment, compared to other racial/ethnic subgroups. This real-world study of clinical outcomes in patients with LPC treated with EBRT suggests substantial disease burden in patients with HR-LPC and highlights the need for additional treatment strategies to improve clinical outcomes in patients with HR-LPC.

Post Hoc Analysis of Rapid and Deep Prostate-specific Antigen Decline and Patient-reported Health-related Quality of Life in SPARTAN and TITAN Patients with Advanced Prostate Cancer

BackgroundAdding apalutamide to androgen-deprivation therapy (ADT) resulted in a rapid (at 3- and 6-mo treatment) and deep prostate-specific antigen (PSA) decline (to ≤0.2 ng/ml or ≥90% from baseline), improved overall survival, reduced risk of disease progression, and prolonged health-related quality of life (HRQoL) in nonmetastatic castration-resistant prostate cancer (nmCRPC) in SPARTAN and metastatic castration-sensitive PC (mCSPC) in TITAN. ObjectiveTo evaluate the association of a rapid, deep PSA decline at 3 and 6 mo achieved with the addition of apalutamide to ADT with patient-reported outcomes (PROs) in SPARTAN and TITAN. Design, setting, and participantsA post hoc analysis of SPARTAN and TITAN PRO data was performed. InterventionApalutamide versus placebo plus concurrent ADT. Outcome measurements and statistical analysisPROs were assessed using Functional Assessment of Cancer Therapy-Prostate (FACT-P; SPARTAN and TITAN), Brief Pain Inventory—Short Form (BPI-SF; TITAN), and Brief Fatigue Inventory (BFI; TITAN) at baseline, prespecified cycles during treatment, and after progression for ≤1 yr. The association between a deep PSA decline at landmark 3 or 6 mo of apalutamide and the time to worsening of PROs was assessed using the Kaplan-Meier methodology and Cox proportional-hazard modeling. Results and limitationsAmong 806 SPARTAN and 525 TITAN apalutamide-treated patients, the median treatment duration was 32.9 and 39.3 mo, respectively. Patients achieving a deep PSA decline at 3 mo had longer time to worsening in FACT-P total, FACT-P physical well-being, BPI-SF worst pain intensity, or BFI worst fatigue intensity. The 6-mo PSA decline results were similar. Limitations of patient characteristics in clinical studies should be considered. ConclusionsAttaining a deep and rapid PSA decline at 3 mo with apalutamide plus ADT was associated with longer preservation of overall HRQoL and physical well-being in nmCRPC and mCSPC. Patient summaryQuality of life is maintained in individuals with advanced prostate cancer who achieve a deep prostate-specific antigen decline at 3 mo of apalutamide plus drugs that lower male sex hormones.

Multi-Institutional Analysis of Metastasis Directed Therapy with or without Androgen Deprivation Therapy in Oligometastatic Castration Sensitive Prostate Cancer.

Several prospective trials in oligometastatic castration sensitive prostate cancer (omCSPC) have shown metastasis-directed therapy (MDT) can delay time to progression and initiation of androgen deprivation therapy (ADT) compared to observation. However, the optimal integration of ADT with MDT remains unclear. Here we report a multi-national, multi-institutional retrospective cohort of omCSPC treated with MDT to characterize the long-term outcomes of patients treated with MDT alone or in combination with ADT. Patients with a controlled primary site and omCSPC (defined as ≤ 5 lesions on conventional imaging) treated with MDT with or without concurrent ADT and with at least 36 months follow-up were retrospectively screened across 13 institutions. The primary endpoints included biochemical progression free survival (bPFS) and radiographic progression free survival (rPFS) calculated using Kaplan-Meier method and stratified by treatment group (MDT alone vs MDT + ADT). Multivariable Cox regression was performed adjusted for variables found to be prognostic on univariate analysis. Among 414 patients screened, a total of 263 patients treated between 2003 and 2018 met inclusion criteria and included. Of these, 105 received MDT alone and 158 received MDT+ADT, with median follow-up of 49.5 and 54.5 months, respectively. The majority were metachronous (90%) and had bone lesions (60%). Median ADT duration was 21.3 months (IQR 12.0- 31.9). Patients who received ADT vs. no ADT had poorer prognostic features including 23% vs. 1% synchronous (p<0.001), and 55% vs 40% Gleason 8-10 (p = 0.012). ADT use was associated with a better 5-year bPFS 24% vs 11% (p<0.0001) and rPFS 41% vs 29% (p<0.001). On multivariable Cox regression adjusting for post-MDT PSA nadir and salvage therapy, ADT use maintained significance for both bPFS (HR 0.51 (0.36, 0.71), p<0.001) and rPFS (HR 0.67, 95% CI 0.46-0.96, p = 0.03). Long-term outcomes with MDT alone suggest a small proportion of patients experience sustained disease control. The addition of ADT appears to improve rPFS, however prospective studies are needed in order to allow for personalization of care in patients with omCSPC.

Impact of Prostate Cancer Treatment with Low Dose Rate Brachytherapy on Testosterone: A Retrospective Analysis

Decrease in serum testosterone counts have been reported in the literature following external beam radiotherapy (EBRT), with a suggested association to low dose irradiation of the testes occurring with historical and modern external techniques. Low dose rate (LDR) brachytherapy has been described as exposing the testes to between 2 and 19 cGy compared with 196-220 cGy with EBRT. This decrease in excess dose is hypothesized to spare post-treatment testosterone decrease and subsequent change in patient-perceived quality of life. Here, we retrospectively evaluate LDR-treated prostate cancer patient testosterone change in a single-institution patient cohort. Patients with prostate cancer who had previously received LDR brachytherapy were identified, and patients with prior baseline total testosterone lab values as well as a lab value within one year post-treatment were identified. Patients receiving concurrent androgen deprivation therapy or EBRT were excluded. The closest baseline values prior to and after LDR treatment were used for before/after comparison. Samples were compared using the paired t-test. A total of 1,463 patients receiving LDR were identified with data available for analysis between 1998 and 2023; of these, 139 patients met the above criteria for analysis. Mean age was 66 (median 67; range: 47 - 79). 5 patients received 110 Gy, 2 received 120 Gy, and the remainder 145 Gy, all conducted with I-125. Total mCi delivered ranged from 20.3 mCi to 56.7 mCi (median 37.6 mCi). Approximately 57% were GS6, 42% G7, and < 1% G8. Approximately 80% of patients had T1c disease, with 19% T2 and < 1% T3a. All patients were cN0M0. Mean pre- and post-treatment testosterone were 385.5 ng/dL and 382.9 (SD: 170.9, 150.9; mean difference 2.65 [95% CI: -15.6, 20.9]), respectively, with no statistical change noted (p = 0.774). Testosterone levels have been reported to drop following definitive EBRT owing to excess dose delivery to the testes. On review of our institutional experience in definitive LDR brachytherapy for patients treated without ADT administration, no change in testosterone levels were noted.

Bipolar Androgen Therapy: When Excess Fuel Extinguishes the Fire.

Androgen deprivation therapy (ADT) remains the cornerstone of advanced prostate cancer treatment. However, the progression towards castration-resistant prostate cancer is inevitable, as the cancer cells reactivate androgen receptor signaling and adapt to the castrate state through autoregulation of the androgen receptor. Additionally, the upfront use of novel hormonal agents such as enzalutamide and abiraterone acetate may result in long-term toxicities and may trigger the selection of AR-independent cells through "Darwinian" treatment-induced pressure. Therefore, it is crucial to develop new strategies to overcome these challenges. Bipolar androgen therapy (BAT) is one such approach that has been devised based on studies demonstrating the paradoxical inhibitory effects of supraphysiologic testosterone on prostate cancer growth, achieved through a variety of mechanisms acting in concert. BAT involves rapidly alternating testosterone levels between supraphysiological and near-castrate levels over a period of a month, achieved through monthly intramuscular injections of testosterone plus concurrent ADT. BAT is effective and well-tolerated, improving quality of life and potentially re-sensitizing patients to previous hormonal therapies after progression. By exploring the mechanisms and clinical evidence for BAT, this review seeks to shed light on its potential as a promising new approach to prostate cancer treatment.

Outcomes after definitive radiation therapy for localized prostate cancer in a national health care delivery system.

Accurate information regarding real-world outcomes after contemporary radiation therapy for localized prostate cancer is important for shared decision-making. Clinically relevant end points at 10years among men treated within a national health care delivery system were examined. National administrative, cancer registry, and electronic health record data were used for patients undergoing definitive radiation therapy with or without concurrent androgen deprivation therapy within the Veterans Health Administration from 2005 to 2015. National Death Index data were used through 2019 for overall and prostate cancer-specific survival and identified date of incident metastatic prostate cancer using a validated natural language processing algorithm. Metastasis-free, prostate cancer-specific, and overall survival using Kaplan-Meier methods were estimated. Among 41,735 men treated with definitive radiation therapy, the median age at diagnosis was 65years and median follow-up was 8.7years. Most had intermediate (42%) and high-risk (33%) disease, with 40% receiving androgen deprivation therapy as part of initial therapy. Unadjusted 10-year metastasis-free survival was 96%, 92%, and 80% for low-, intermediate-, and high-risk disease. Similarly, unadjusted 10-year prostate cancer-specific survival was 98%, 97%, and 90% for low-, intermediate-, and high-risk disease. The unadjusted overall survival was lower across increasing disease risk categories at 77%, 71%, and 62% for low-, intermediate-, and high-risk disease (p<.001). These data provide population-based 10-year benchmarks for clinically relevant end points, including metastasis-free survival, among patients with localized prostate cancer undergoing radiation therapy using contemporary techniques. The survival rates for high-risk disease in particular suggest that outcomes have recently improved.

Neoadjuvant versus Concurrent Androgen Deprivation Therapy in Localized Prostate Cancer Treated with Radiotherapy: A Systematic Review of the Literature.

There is an ongoing debate on the optimal sequencing of androgen deprivation therapy (ADT) and radiotherapy (RT) in patients with localized prostate cancer (PCa). Recent data favors concurrent ADT and RT over the neoadjuvant approach. We conducted a systematic review in PubMed, EMBASE, and Cochrane Databases assessing the combination and optimal sequencing of ADT and RT for Intermediate-Risk (IR) and High-Risk (HR) PCa. Twenty randomized control trials, one abstract, one individual patient data meta-analysis, and two retrospective studies were selected. HR PCa patients had improved survival outcomes with RT and ADT, particularly when a long-course Neoadjuvant-Concurrent-Adjuvant ADT was used. This benefit was seen in IR PCa when adding short-course ADT, although less consistently. The best available evidence indicates that concurrent over neoadjuvant sequencing is associated with better metastases-free survival at 15 years. Although most patients had IR PCa, HR participants may have been undertreated with short-course ADT and the absence of pelvic RT. Conversely, retrospective data suggests a survival benefit when using the neoadjuvant approach in HR PCa patients. The available literature supports concurrent ADT and RT initiation for IR PCa. Neoadjuvant-concurrent-adjuvant sequencing should remain the standard approach for HR PCa and is an option for IR PCa.

Clinical outcomes in patients with metastatic castrate-resistant prostate cancer treated with abiraterone with or without ongoing androgen deprivation therapy: A retrospective case-control study.

Abiraterone and concurrent androgen deprivation therapy (ADT) are used in the treatment of patients with metastatic castration-resistant prostate cancer. Recently, it has been suggested that the use of abiraterone alone (without ADT) may have comparable efficacy to abiraterone with ongoing ADT. Here, we sought to assess the impact of ADT cessation in patients beginning abiraterone for castration-resistant prostate cancer. We identified 39 patients at our institution who received abiraterone alone (with discontinuation of ADT) between 2011 and 2022. We then procured a comparable group of 39 patients (matched by age, Gleason score, and prostate-specific antigen [PSA] level) who received abiraterone with ongoing ADT during the same period. We assessed and compared clinical outcomes in the two groups (abiraterone-alone vs. abiraterone-ADT) with respect to PSA response rates, PSA progression-free survival, and overall survival. Results were adjusted using Cox proportional-hazards multivariable models. The median PSA before treatment initiation was 12.7 (range: 0.2-199) ng/mL in the abiraterone-alone group and 15.5 (range: 0.6-212) ng/mL in the abiraterone-ADT group. Use of abiraterone alone adequately suppressed testosterone levels in 35/37 (94.6%) patients. Patients receiving abiraterone alone had a median PSA reduction of 80.2% versus 79.5% in patients receiving abiraterone plus ADT. The median PSA progression-free survival in patients receiving abiraterone alone was 27.4versus 25.8 months in patients receiving abiraterone plus ADT (hazard ratio [HR] 1.10; 95% confidence interval [CI] 0.65-1.71; p = 0.82). In addition, abiraterone alone was associated with an overall survival of 3.6versus 3.1 years in patients receiving abiraterone plus ADT (HR 0.90; 95% CI 0.50-1.62; p = 0.72). There were no differences in PFS or OS between groups after performing Cox multivariable regression analyses. Use of abiraterone alone was associated with comparable clinical outcomes to patients who received abiraterone together with ADT. Further prospective studies are warranted to evaluate the impact of abiraterone alone on treatment outcomes and cost savings.

Development and Validation of a Multi-institutional Nomogram of Outcomes for PSMA-PET–Based Salvage Radiotherapy for Recurrent Prostate Cancer

Prostate-specific antigen membrane positron-emission tomography (PSMA-PET) is increasingly used to guide salvage radiotherapy (sRT) after radical prostatectomy for patients with recurrent or persistent prostate cancer. To develop and validate a nomogram for prediction of freedom from biochemical failure (FFBF) after PSMA-PET-based sRT. This retrospective cohort study included 1029 patients with prostate cancer treated between July 1, 2013, and June 30, 2020, at 11 centers from 5 countries. The initial database consisted of 1221 patients. All patients had a PSMA-PET scan prior to sRT. Data were analyzed in November 2022. Patients with a detectable post-radical prostatectomy prostate-specific antigen (PSA) level treated with sRT to the prostatic fossa with or without additional sRT to pelvic lymphatics or concurrent androgen deprivation therapy (ADT) were eligible. The FFBF rate was estimated, and a predictive nomogram was generated and validated. Biochemical relapse was defined as a PSA nadir of 0.2 ng/mL after sRT. In the nomogram creation and validation process, 1029 patients (median age at sRT, 70 years [IQR, 64-74 years]) were included and further divided into a training set (n = 708), internal validation set (n = 271), and external outlier validation set (n = 50). The median follow-up was 32 months (IQR, 21-45 months). Based on the PSMA-PET scan prior to sRT, 437 patients (42.5%) had local recurrences and 313 patients (30.4%) had nodal recurrences. Pelvic lymphatics were electively irradiated for 395 patients (38.4%). All patients received sRT to the prostatic fossa: 103 (10.0%) received a dose of less than 66 Gy, 551 (53.5%) received a dose of 66 to 70 Gy, and 375 (36.5%) received a dose of more than 70 Gy. Androgen deprivation therapy was given to 325 (31.6%) patients. On multivariable Cox proportional hazards regression analysis, pre-sRT PSA level (hazard ratio [HR], 1.80 [95% CI, 1.41-2.31]), International Society of Urological Pathology grade in surgery specimen (grade 5 vs 1+2: HR, 2.39 [95% CI, 1.63-3.50], pT stage (pT3b+pT4 vs pT2: HR, 1.91 [95% CI, 1.39-2.67]), surgical margins (R0 vs R1+R2+Rx: HR, 0.60 [95% CI, 0.48-0.78]), ADT use (HR, 0.49 [95% CI, 0.37-0.65]), sRT dose (>70 vs ≤66 Gy: HR, 0.44 [95% CI, 0.29-0.67]), and nodal recurrence detected on PSMA-PET scans (HR, 1.42 [95% CI, 1.09-1.85]) were associated with FFBF. The mean (SD) nomogram concordance index for FFBF was 0.72 (0.06) for the internal validation cohort and 0.67 (0.11) in the external outlier validation cohort. This cohort study of patients with prostate cancer presents an internally and externally validated nomogram that estimated individual patient outcomes after PSMA-PET-guided sRT.

MP29-03 MULTI-INSTITUTIONAL ANALYSIS OF METASTASIS DIRECTED THERAPY WITH OR WITHOUT ANDROGEN DEPRIVATION THERAPY IN OLIGOMETASTATIC CASTRATION SENSITIVE PROSTATE CANCER

MP29-03 MULTI-INSTITUTIONAL ANALYSIS OF METASTASIS DIRECTED THERAPY WITH OR WITHOUT ANDROGEN DEPRIVATION THERAPY IN OLIGOMETASTATIC CASTRATION SENSITIVE PROSTATE CANCER

National population-based survival estimates after definitive radiation therapy for prostate cancer.

395 Background: Understanding contemporary radiation therapy outcomes for prostate cancer (i.e., metastasis, death) is important for shared decision-making and setting expectations for patients and providers. Unfortunately, long-term outcome estimates are often derived from meta-analyses of outdated prospective clinical trials or population-based data lacking reliable clinical details (e.g., incident metastatic disease). For these reasons, we used a recently validated, natural language processing algorithm to identify incident metastatic prostate cancer within the electronic medical records of men treated with radiation therapy for localized prostate cancer in order to conduct an innovative and contemporary population-based survival outcomes study. Methods: We used national administrative, cancer registry, and electronic health record data for patients undergoing definitive radiation therapy with or without concurrent androgen deprivation therapy (ADT) within the Veterans Health Administration from 2005 to 2015. We used National Death Index data through 2019 for overall and prostate cancer-specific survival, and identified the date of incident metastatic prostate cancer using a validated natural language processing algorithm. We estimated metastasis-free, prostate cancer-specific, and overall survival using Kaplan-Meier methods. Results: We identified 41,876 patients treated with definitive radiation therapy for prostate cancer from 2005 through 2015, and followed them for over 8 years (follow up, median, 8.7 years, age at diagnosis, median, 65 years). Most patients had intermediate (42%) and high risk (33%) disease, with nearly half treated with ADT as part of initial therapy (44%). Unadjusted 10-year metastasis-free survival was 96%, 92%, and 80% for low, intermediate, and high risk disease. Similarly, unadjusted 10-year prostate cancer-specific survival was 98%, 97%, and 90% for low, intermediate, and high risk disease. Unadjusted overall survival was lower across disease risk categories at 77%, 71%, and 62% for low, intermediate, and high risk disease. Conclusions: These data provide population-based benchmarks for clinically relevant endpoints, including metastasis-free survival, among patients with low, intermediate, and high risk prostate cancer undergoing radiation therapy using contemporary techniques. The survival rates for high risk disease, in particular, compare favorably with historical outcomes.

TRIUMPH: Phase II trial of rucaparib monotherapy in patients with metastatic hormone-sensitive prostate cancer harboring germline DNA repair gene mutations.

190 Background: Androgen deprivation therapy (ADT) is the backbone of treatment for patients (pts) with metastatic prostate cancer (PCa), but many pts find this difficult to tolerate. Treatment with non-castrating regimens may avoid or delay the toxicities of hormonal therapy. The activity of PARP inhibitors (PARPi) in pts with homologous recombination DNA-repair (HRD) mutations (muts) and metastatic castration-resistant PCa has been established. We hypothesized here that the benefit of ARPi can be maintained in the absence of ADT in a biomarker-selected (HRD mutated) population with PCa. We designed a Phase 2 study in men with hormone-naïve, metastatic PCa who harbored a germline HRD mut treated with rucaparib monotherapy (without ADT). Methods: This was a multi-center, single arm Phase 2 study (NCT03413995) in men with asymptomatic hormone-sensitive metastatic PCa who received rucaparib 600mg by mouth daily. During consenting, pts were informed and had to opt out of ADT-based therapy. Pts must have had a germline mutation in an HRD gene on clinical-grade testing. The primary endpoint was confirmed PSA50 response rate. Key secondary endpoints included safety, objective response rate (ORR), and radiographic progression-free survival (rPFS). The trial was designed to detect a 25% absolute increase in PSA50 response from a null of 50%. Results: 12 pts were enrolled, 7 with BRCA1/2 and 5 with CHEK2 muts. The confirmed PSA50 response rate to rucaparib was 41.7% (N=5/12, 95% CI: 19.3-68.1%), which did not meet the pre-specified efficacy boundary to enroll additional patients to 2nd stage. In pts with measurable disease, the ORR was 60% (N=3/5, all with BRCA2). Median rPFS on rucaparib was 10.3 months (95% CI: 4.0 mo - NR). At the time of the interim analysis, 3 pts remained on study. The majority of adverse events (AE) were Grade ≤2 and expected. Translational studies are ongoing. Conclusions: Rucaparib can induce clinical responses in a biomarker-selected PCa population without concurrent ADT. However, the pre-specified threshold of PSA50 response was not met. Although durable responses were observed in a subset of pts, PARPi without ADT in metastatic hormone sensitive PCa will not be pursued. Clinical trial information: NCT03413995 . [Table: see text]

Development and validation of a multi-institutional nomogram of outcomes for PSMA-PET–based salvage radiotherapy in recurrent prostate cancer.

355 Background: We aimed to develop and to validate a multi-institutional nomogram of outcomes for PSMA-PET based salvage radiotherapy (sRT) following radical prostatectomy (RP) for patients with recurrent or persistent prostate cancer (PCa). Methods: Data from patients with a detectable post-RP prostate-specific antigen (PSA) treated with sRT with or without concurrent androgen-deprivation therapy (ADT) were obtained from 11 academic institutions from 5 countries. All patients had a PSMA-PET scan prior sRT and patients with distant metastases on PET were excluded from this analysis. The freedom from biochemical failure (FFBF) rate was estimated, and a predictive nomogram was generated and validated. Biochemical relapse (BR) was defined as PSA nadir +0.2 ng/ml after sRT. Results: Overall, 1029 patients (training set n=821, external validation set n=208) with a median follow-up of 33 months were included. On PSMA-PET, 427 (42%) and 313 (30%) patients had local and nodal recurrences, respectively. Elective pelvic lymphatics were irradiated in 368 (36%) patients. All patients received sRT to the prostatic fossa receiving a dose of &lt;66 Gy, 66-70 Gy and &gt;70 Gy in 103 (10%), 551 (54%) and 375 (36%) patients, respectively. Androgen deprivation therapy (ADT) was given in 325 (32%) patients. On multivariable Cox regression analysis, pre-SRT PSA, ISUP grade, pT stage, surgical margins, ADT use, sRT dose and nodal recurrence on PSMA PET were associated with FFBF. The nomogram concordance index was 0.7 for FFBF in external validation. Conclusions: We present an externally validated contemporary nomogram which can estimate individual patient outcomes after PSMA-PET guided sRT. Positive lymph nodes on PSMA-PET seem to be a new risk factor for BR after sRT.

Metformin use and hospital attendance-related resources utilization among diabetic patients with prostate cancer on androgen deprivation therapy: A population-based cohort study.

Androgen deprivation therapy (ADT), used increasingly in the treatment of prostate cancer (PCa), negatively influences glycemic control in diabetes and is associated with an increased risk of diabetes complications where hospitalization commonly ensues. Metformin could decrease the metabolic consequences of ADT and enhance its effect. This study examined the association of metformin use with healthcare resources utilization among diabetic, PCa patients receiving ADT. Diabetic adults with PCa on ADT in Hong Kong between December 1999 and March 2021 were identified. Patients with <6months of concurrent metformin and ADT use were excluded. All included patients were followed up until September 2021. The outcomes were hospital attendances and related costs. In total, 1,284 metformin users and 687 non-users were studied. Over 8,045 person-years, 9,049 accident and emergency (A&E), and 21,262 inpatient attendances, with 11,2781 days of hospitalization were observed. Metformin users had significantly fewer A&E attendances (incidence rate ratio (IRR): 0.61 [95% confidence interval 0.54-0.69], p < 0.001), inpatient attendances (IRR: 0.57 [0.48-0.67], p < 0.001), and days of hospitalization (IRR: 0.55 [0.42-0.72], p < 0.001). Annual attendance costs were lower for metformin users than non-users (cost ratio: 0.28 [0.10-0.80], p=0.017). Metformin use was associated with decreased hospital attendances, days of hospitalization, and associated costs, which could help reduce healthcare resource utilization following ADT in the treatment of PCa.

Immediate radiotherapy versus observation in patients with node-positive prostate cancer after radical prostatectomy.

The optimal management of node-positive (pN1) prostate cancer following radical prostatectomy (RP) remains uncertain. Despite randomized evidence, utilization of immediate, life-long androgen deprivation therapy (ADT) remains poor, and recent trials of early salvage radiotherapy included only a minority of pN1 patients. We therefore emulated a hypothetical pragmatic trial of adjuvant radiotherapy versus observation in men with pN1 prostate cancer. Using the RADICALS-RT trial to inform the design of a hypothetical trial, we identified men aged 50-69 years with pT2-3 Rany pN1 M0, pre-treatment PSA < 50 ng/mL prostate cancer in the NCDB from 2006 to 2015 treated with 60-72 Gy of adjuvant RT (aRT) ±ADT within 26 weeks of RP or observation. After estimating a propensity score for receipt of aRT, we estimated absolute and relative treatment effects using stabilized inverse probability of treatment (sIPW) re-weighting. In total, 3510 patients were included in the study, of whom 587 (17%) received aRT (73% with concurrent ADT). Median follow-up was40.0 -months, during which 333 deaths occurred. After sIPW re-weighting, baseline characteristics were well-balanced. Adjusted overall survival (OS) was 93% versus 89% at 5-years and 82% versus 79% at 7-years for aRT versus observation (p = 0.11). In IPW-reweighted Cox regression, aRT was associated with a lower risk of all-cause mortality (ACM) than observation, but this did not reach statistical significance (HR 0.70 p = 0.06). In analyses examining heterogeneity of treatment effects, aRT was associated with improved ACM only for men with Gleason 8-10 disease (HR 0.59, p = 0.01), ≥2 positive LNs (HR 0.49, p = 0.04 for 2 positive LNs; HR 0.42, p = 0.01 for ≥3 positive LNs), or negative surgical margins (HR 0.50, p = 0.02). In observational analyses designed to emulate a hypothetical target trial of aRT versus observation in pN1 prostate cancer, aRT was associated with improved OS only for men with Gleason 8-10 disease, ≥2 positive LNs, or negative surgical margins.

Dynamic Change in Patient Reported Quality of Life is a Predictor for Survival in Localized Prostate Cancer: Exploratory Analysis from a Phase III Randomized Controlled Trial

<h3>Purpose/Objective(s)</h3> Patient reported quality of life (QOL) outcomes are pivotal endpoints to determine treatment efficacy and safety. However, it remains unknown if treatment induced change in patient reported QOL outcomes correlate with survival in localized prostate cancer (LPCa). We performed an exploratory analysis of a phase III randomized controlled study to determine the association of treatment induced dynamic change in patient reported global QOL with long-term overall survival (OS) and disease-free survival (DFS) in LPCa treated with radiotherapy (RT) and androgen deprivation therapy (ADT). <h3>Materials/Methods</h3> LPCa patients with Gleason score ≤7, clinical stage T1b-T3a, and PSA <30 ng/mL were randomized to neoadjuvant and concurrent ADT for 6 mos starting 4 mos before prostate RT or concomitant and adjuvant ADT for 6 mos starting concurrently with RT. Patient reported QOL outcomes were collected using EORTC QOL questionnaires. We used the global QOL (G-QOL) score from C30 questionnaire. Increase in G-QOL score indicated improvement in global QOL. To capture the association between the dynamic change in the G-QOL of each patient and the hazard of outcome, we utilized the framework of multivariate joint modeling for longitudinal and survival outcomes. For the time-to-event submodel, a Cox proportional hazard regression model was built with covariables including treatment arm, baseline PSA, tumor stage, Gleason score, and age. For the longitudinal submodel, a linear mixed effect model was built with an interaction term for treatment arm and time of evaluation in addition to fixed covariables - treatment arm, time of evaluation, baseline G-QOL score and age. Time of assessment was included as a random slope while patients were included as random intercepts in the mixed models. The two submodels were linked through a random effect. Baseline hazard was modeled using penalized splines. A two-sided p-value <0.025 was chosen to be the threshold for statistical significance. <h3>Results</h3> A total of 388 patients were eligible for this study – 191 belonged to the neoadjuvant arm while 197 to the adjuvant arm. At a median follow-up of 148 mos, a total of 133 deaths were recorded. On joint modelling, an increase in G-QOL score by 10 units (the threshold for clinically meaningful change) was associated with a 11.2% decrease in the hazard of death (hazard ratio [HR] per 1 unit increase G-QOL: 0.988, 95% CI: 0.980-0.996; p=0.007). An increase in G-QOL score by 10 units was associated with 10% decrease in the hazard of progression or death (HR per 1 unit increase in G-QOL: 0.990; 95% CI: 0.984-0.999; p=0.023). <h3>Conclusion</h3> Treatment induced improvement in global QOL is a predictor for improved DFS and OS in LPCa. This suggests a significant interplay of patient-reported quality of life and quantity of life in LPCa which could mainly be driven by the non-cancer specific mortality in this patient population. Judicious use of these QOL metrics could guide risk stratification and potentially inform treatment decision in these patients