Phillips, Ryan

Introduction: As interest in metastasis-directed therapy (MDT) for prostate cancer (PCa) grows, exploring indications and patient selection is increasingly more important. Thus far, few studies have described long-term outcomes after surgical MDT in those with disease recurrence involving the lung. The objective of our study was to compare the cumulative incidence of cancer-related death by treatment modality in men with metachronous pulmonary metastases from PCa. Methods: In a single-institution retrospective study, we identified 75 men from the prospectively maintained Mayo Clinic C-11 Positron Emission Tomography Choline PCa registry with recurrent prostate cancer involving the lung but no other visceral organs. Patients were categorized into 3 groups based on treatment modalities: wedge resection ± hormonal therapy, chemohormonal therapy, and hormonal therapy alone. The risk of cancer-related death after treatment at the time of lung metastases was reported as cumulative incidence estimates. Non–cancer-related deaths were treated as a competing risk of death. A univariate Cox regression model was conducted to assess the impact of treatment modality on the risk of cancer-related death. Results: At the time of lung metastasis, the median age was 69.5 years, and the median (IQR) prostate-specific antigen was 4 (1.3-8.6) ng/ml. Forty-seven patients (62.7%) had hormone-sensitive disease, and 28 patients (37.3%) had hormone-resistant disease. A total of 26 patients (34.7%) were treated with wedge resection ± hormonal therapy, 27 (36%) with chemohormonal therapy, and 22 (29.3%) with hormonal therapy alone. The median (IQR) follow-up time was 50.3 (31.1-78.4) months, and 21 patients (28%) died. Patients who were treated with wedge resection ± hormonal therapy had lower rated of cancer-related death compared with those who received chemohormonal therapy (Hazard Ratio [HR]: 4.14, 95% CI: 1.01-16.96, P = .048) or hormonal therapy alone (HR: 6.37, 95% CI: 1.72-23.54, P = .005). Conclusion: This exploratory analysis supports the safety and feasibility of surgical metastasis-directed therapy in select patients with recurrent prostate cancer involving the lung. Favorable long-term survival provides justification for further evaluation of this approach.

5094 Background: In prior studies, basal vs. luminal differentiation portends differential response to a) androgen suppression (AS) duration for high-risk prostate cancer (PCa) (NRG-GU-TS006) and b) docetaxel chemotherapy (CT) and AS for metastatic hormone-sensitive disease (CHAARTED). In NRG-GU-TS006, basal tumors appeared to benefit the most from longer duration of AS while those with luminal subtype did not whereas, in CHAARTED, luminal subtype had greater benefit from addition of CT. Herein, we examined basal-luminal subtyping to predict differential response to the addition of CT in the setting of high-risk PCa treated with AS and definitive radiotherapy (AS + RT) in NRG/RTOG 0521. Methods: Per pre-specified and approved NCI analysis plan (Navigator #1061), we obtained available NRG biobank biopsy specimens from patients enrolled on the NRG/RTOG 0521 phase III trial, which randomized patients to AS + RT +/- CT. The highest-grade tumors were profiled on clinical-grade whole-transcriptome arrays (Veracyte, San Diego, CA). Basal-luminal subtypes were generated using a 215-gene PCa subtyping classifier (PSC), a second generation PAM50 basal-luminal model. Treatment effects in Luminal Proliferating (LP) and non-LP subtypes were examined with Cox (for overall survival, OS, and metastasis-free survival, MFS) and Fine & Gray (for distant metastasis, DM) multivariable (MVA) models adjusted for age and trial risk stratification, as well as with restricted mean survival times (RMST). Results: Of 183 samples available for analysis (91 from control and 92 from the CT arm), 52 (28%) were classified as LP subtype. Median follow-up for OS was 9.9 years. No significant differences in clinical or pathological variables were observed between LP and non-LP subtypes. In MVA, we did not detect any significant LP subtype-by-CT treatment interaction but observed evidence of non-proportional hazards (Grambsch-Therneau test, p<0.05). In unselected patients, 5- and 10-year RMST difference between the arms was 0.9 (95% CI [-1.5, 3.4], p=0.46) and 5.7 (95% CI [-2.5, 13.9], p=0.17) months of OS. Stratifying by tumor subtype, at 5 years the RMST difference in months was 3.8 (95% CI [0.3, 7.2], p=0.03) for LP and -0.2 ([-3.4, 2.9], p=0.89) for non-LP. The RMST difference in months at 10-years was 13.7 (95% CI [-0.2, 27.5], p=0.053) for LP and 2.5 ([-7.6, 12.5], p=0.63) for non-LP. Conclusions: In pre-treatment biopsy samples from a Phase 3 trial cohort of localized high-risk men, luminal-basal subtyping of tumors demonstrated differential response to docetaxel CT. Similar to results from the CHAARTED trial of metastatic disease, LP tumors may derive greater benefit from addition of CT. Validation of these findings may enable effective earlier use of CT in men with PCa.

199 Background: Contained within the spectrum of metastatic cancer is an oligometastatic state where metastases are limited in number. Recent prospective data have shown that metastasis directed therapy (MDT) can alter the natural history of oligometastatic disease. In hormone-sensitive prostate cancer (HSPC), the positive clinical effect of MDT has been observed by the phase II STOMP and ORIOLE trials. Circulating tumor cells (CTCs) are a likely origin of the formation of macroscopic metastases. CTCs thus may provide an approach for identifying subgroups of patients with oligometastatic HSPC (oligoHSPC) that would benefit most from MDT. Our main goal was to evaluate the association between presence of CTCs at baseline or day 180 with clinical outcomes in the ORIOLE trial. Methods: ORIOLE was a phase II trial randomizing men with recurrent oligoHSPC with 1-3 metastases to observation (Obs) versus stereotactic ablative radiotherapy (SABR) MDT. Blood samples were prospectively collected at baseline and day 180. Progression-free survival (PFS) was a composite endpoint including any of the following: a PSA rise of at least 2 ng/dL and 25% above nadir; radiologic progression by CT, MRI or bone scan (RECIST v1.1); symptomatic progression of disease; initiation of ADT; or death. Patient blood samples were shipped for analysis on Epic Sciences liquid biopsy platform (Epic Sciences, San Diego, CA). Machine learning algorithms identified CTCs and characterized androgen receptor (AR) expression. Comparisons of patient and tumor characteristics between the groups were performed by two-sample t-tests. Survival curves were generated using the Kaplan-Meier method and p-values were calculated using log-rank test. Analysis was performed using SPSS version 28. Results: A total of 82 samples were collected: 70 from the SABR arm (35 baseline and 35 on day 180) and 12 Obs (7 baseline and 5 on day 180). CTCs were detected in 30/42 samples at baseline (71%, AR+= 7) and in 26/40 samples on day 180 (65%, AR+= 9). In the SABR group there was no difference between CTC+ versus CTC- and AR + versus AR- groups for PSA evaluated at baseline, day 90 or day 180 or Gleason score. With a median follow-up of 41.7 months, PFS was significantly lower in the patients with AR+ versus AR- CTCs at baseline in the SABR arm (p = 0.011, mean PFS: AR+ = 9.3 months, AR- = 27.1 months). The mean biochemical failure-free survival was AR+= 12.9 versus AR-= 29.2 months (p = 0.058). Conclusions: Our preliminary results demonstrate an association between AR+ CTCs at baseline and Day 180 with clinical outcomes following SABR MDT in oligoHSPC. This is the first report examining baseline and dynamic presence of CTCs in oligoHSPC treated from a prospective randomized trial of SABR. Longer follow-up, further analysis and a greater number of patients are needed for a more comprehensive conclusion.

Abstract Extra copies of centrosomes are frequently observed in cancer cells. To survive and proliferate, cancer cells have developed strategies to cluster extra-centrosomes to form bipolar mitotic spindles. The aim of this study was to investigate whether centrosome clustering (CC) inhibition (CCi) would preferentially radiosensitize non–small cell lung cancer (NSCLC). Griseofulvin (GF; FDA-approved treatment) inhibits CC, and combined with radiation treatment (RT), resulted in a significant increase in the number of NSCLC cells with multipolar spindles, and decreased cell viability and colony formation ability in vitro. In vivo, GF treatment was well tolerated by mice, and the combined therapy of GF and radiation treatment resulted in a significant tumor growth delay. Both GF and radiation treatment also induced the generation of micronuclei (MN) in vitro and in vivo and activated cyclic GMP-AMP synthase (cGAS) in NSCLC cells. A significant increase in downstream cGAS-STING pathway activation was seen after combination treatment in A549 radioresistant cells that was dependent on cGAS. In conclusion, GF increased radiation treatment efficacy in lung cancer preclinical models in vitro and in vivo. This effect may be associated with the generation of MN and the activation of cGAS. These data suggest that the combination therapy of CCi, radiation treatment, and immunotherapy could be a promising strategy to treat NSCLC.

BackgroundPatients with high‐risk prostate cancer (HRPC) have multiple accepted treatment options. Because there is no overall survival benefit of one option over another, appropriate treatment must consider patient life expectancy, quality of life, and cost.MethodsThe authors compared quality‐adjusted life years (QALYs) and cost effectiveness among treatment options for HRPC using a Markov model with three treatment arms: (1) external‐beam radiotherapy (EBRT) delivered with 20 fractions, (2) EBRT with 23 fractions followed by low‐dose‐rate (LDR) brachytherapy boost, or (3) radical prostatectomy alone. An exploratory analysis considered a simultaneous integrated boost according to the FLAME trial (ClinicalTrials.gov identifier NCT01168479).ResultsTreatment strategies were compared using the incremental cost‐effectiveness ratio (ICER). EBRT with LDR brachytherapy boost was a cost‐effective strategy (ICER, $20,929 per QALY gained). These results were most sensitive to variations in the biochemical failure rate. However, the results still demonstrated cost effectiveness for the brachytherapy boost paradigm, regardless of any tested parameter ranges. Probabilistic sensitivity analysis demonstrated that EBRT with LDR brachytherapy was favored in 52% of 100,000 Monte Carlo iterations. In an exploratory analysis, EBRT with a simultaneous integrated boost was also a cost‐effective strategy, resulting in an ICER of $62,607 per QALY gained; however, it was not cost effective compared with EBRT plus LDR brachytherapy boost.ConclusionsEBRT with LDR brachytherapy boost may be a cost‐effective treatment strategy compared with EBRT alone and radical prostatectomy for HRPC, demonstrating high‐value care. The current analysis suggests that a reduction in biochemical failure alone can result in cost‐effective care, despite no change in overall survival.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co‐primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. The initial STOMP and ORIOLE trial reports suggested that metastasis-directed therapy (MDT) in oligometastatic castration-sensitive prostate cancer (omCSPC) was associated with improved treatment outcomes. Here, we present long-term outcomes of MDT in omCSPC by pooling STOMP and ORIOLE and assess the ability of a high-risk mutational signature to risk stratify outcomes after MDT. The primary end point was progression-free survival (PFS) calculated using the Kaplan-Meier method. High-risk mutations were defined as pathogenic somatic mutations within ATM, BRCA1/ 2, Rb1, or TP53. The median follow-up for the whole group was 52.5 months. Median PFS was prolonged with MDT compared with observation (pooled hazard ratio [HR], 0.44; 95% CI, 0.29 to 0.66; P value < .001), with the largest benefit of MDT in patients with a high-risk mutation (HR high-risk, 0.05; HR no high-risk, 0.42; P value for interaction: .12). Within the MDT cohort, the PFS was 13.4 months in those without a high-risk mutation, compared with 7.5 months in those with a high-risk mutation (HR, 0.53; 95% CI, 0.25 to 1.11; P = .09). Long-term outcomes from the only two randomized trials in omCSPC suggest a sustained clinical benefit to MDT over observation. A high-risk mutational signature may help risk stratify treatment outcomes after MDT.

5025 Background: Prospective reports suggest metastasis directed therapy (MDT) in oligometastatic castration sensitive prostate cancer (omCSPC) is associated with improved treatment outcomes. Here we present long term outcomes of the phase II STOMP and ORIOLE trials and assess the ability of a high-risk (HiRi) mutational signature to provide prognostic and predictive information regarding MDT response. Methods: Patients with omCSPC (< 3 lesions) enrolled on STOMP (n = 62) and ORIOLE (n = 54) randomized to MDT or observation were pooled. The primary endpoint was progression-free survival (PFS) defined as either PSA or radiographic progression, initiation of androgen deprivation, or death. Secondary endpoint was radiographic PFS (rPFS) defined as radiographic progression or death. Both were calculated using the Kaplan-Meier method and stratified by treatment group. Next generation sequencing (NGS) was performed to identify a HiRi mutational signature defined as pathogenic mutations within ATM, BRCA1/2, Rb1, or TP53. Cox proportional hazards regressions were fit to calculate hazard ratios (HR) and assess the prognostic and predictive values of HiRi mutational status. Results: Median follow-up was 52.5 months. Median PFS was prolonged with MDT (11.9 months) compared to observation (5.9 months) with a pooled HR of 0.44 (95% CI, 0.29 – 0.66, p-value < 0.001). MDT was associated with PSA decrease in a majority of patients (84%) as compared to the observation group (41%). On NGS, the incidence of a pathogenic mutation in a HiRi gene was 24.3%. HiRi mutation was prognostic for PFS -- in those without a HiRi mutation median PFS was 11.9 months compared to 5.9 months in those with a HiRi mutation (HR of 1.74, p = 0.06). HiRi mutation was also prognostic for rPFS -- those without a high-risk mutation experienced median rPFS of 22.6 months compared to 10.0 months in those with a high-risk mutation (HR 2.62, p < 0.01). Tumors without a HiRi mutation treated with MDT experienced the longest PFS (13.4 months) while those with a HiRi randomized to observation experienced the shortest PFS (2.8 months). Stratifying by both treatment arms and HiRi status appeared to show a differential benefit to MDT, with those with HiRi mutations experiencing a larger relative magnitude of benefit to treatment: (HiRi mutation: HR of 0.05, p < 0.01; no HiRi mutation: HR of 0.42, p = 0.01; p interaction, 0.12) suggesting a HiRi mutational status can provide information regarding differential response to treatment. Conclusions: Long-term outcomes from the only two randomized trials in omCSPC suggest a sustained benefit to MDT over observation. A HiRi mutational signature appears prognostic for outcomes in omCSPC and those with HiRi might have a relatively larger magnitude of response to MDT. Future studies are needed to optimize patient selection. Clinical trial information: NCT02680587.

5011 Background: Emerging data suggest metastasis-directed therapy (MDT) improves outcomes in patients with oligometastatic castration-sensitive prostate cancer (omCSPC). Prostate-specific membrane antigen positron emission tomography (PSMA-PET/CT) can detect occult metastatic disease and has been proposed as a biomarker for treatment response. Herein we identify and validate a PSMA-PET biomarker for clinical outcomes following MDT in omCSPC. Methods: This was an international multi-institutional retrospective study of two completely independent cohorts of men with omCSPC, defined as ≤3 lesions, treated with metastasis-directed stereotactic ablative radiation therapy (SABR) who underwent PSMA-PET/CT prior to and 3-6 months after treatment. Pre- and post-SABR PSMA-PET/CT standardized uptake value (SUV) was measured for all lesions and PSMA response defined discretely using a cutpoint of ≥ 30% decrease in SUVmax. PSMA-PET response was correlated with lesion local control (LLC), radiographic progression-free survival (rPFS) defined using conventional and PET imaging, and metastasis-free survival (MFS) defined by conventional imaging alone. Results: A total of 131 patients with 261 treated metastases were included in the analysis, with median follow-up of 29 months (IQR 18.5-41.3). Following SABR, 78.4% of lesions experienced a partial or complete PSMA response. Multivariable analysis demonstrated SUV response significantly associated with improved LLC (HR = 9.97, 95%CI 3.92-25.4; p < 0.01). Patients with PSMA response in all lesions experienced significantly better rPFS (HR = 0.49, 95%CI 0.26-0.92; p = 0.03) compared to their counterparts and this maintained significance within both the discovery (p < 0.01) and validation (p = 0.01) cohorts. Within the discovery cohort, patients with PSMA response in all lesions also experienced significantly improved MFS (HR = 0.24, 95%CI 0.07-0.85; p = 0.03); analysis of the independent validation cohort is ongoing. Conclusions: Following SABR, PSMA-PET response is a robust and externally validated radiographic biomarker for rPFS and appears to be associated with MFS pending validation. This approach holds promise for guiding clinical management of omCSPC.