Longitudinal measurement of subcutaneous and intratibial human prostate cancer xenograft growth and response to ionizing radiation by plasma Alu and LINE-1 ctDNA: A comparison to standard methods

BACKGROUND

Current preclinical models of metastatic prostate cancer (PCa) require sophisticated technologies and/or genetically engineered cells for the noninvasive monitoring of tumors in remote sites, such as bone. Recent developments in circulating tumor DNA (ctDNA) analysis provide an alternative method for noninvasive tumor monitoring at a low cost. Here, we sought to evaluate human Alu and LINE-1 ctDNA for the longitudinal measurement of subcutaneous and intratibial human PCa xenograft growth and response to ionizing radiation (IR) through comparison with standard slide caliper and bioluminescence measurements.

MATERIAL AND METHODS

Intratibial and subcutaneous xenografts were established in male athymic nude mice using LNCaP cells that stably express firefly luciferase. A subset of tumors was treated with a single dose of IR (CT-guided focal IR, 6 Gy). Tumor measurements were simultaneously taken by slide caliper (subcutaneous only), in vivo bioluminescence imaging, and quantitative real-time PCR (qPCR) of human-specific Alu and LINE-1 ctDNA for several weeks.

RESULTS

Levels of ctDNA and bioluminescence increased concordantly with subcutaneous and intratibial tumor growth. A statistically significant correlation (Spearman) was observed between ctDNA and subcutaneous tumor volume (LINE-1, r = .94 and Alu, r = .95, p < .0001), ctDNA and bioluminescence (LINE-1, r = .66 and Alu, r = .60, p < .002), and bioluminescence and tumor volume (r = .66, p = .0003). Bioluminescence and ctDNA were also significantly correlated in intratibial tumors (LINE-1, r = .82 and Alu, r = .81, p < .0001). Following external beam IR, the tumor responses varied briefly by method of measurement, but followed a similar trend. Statistically significant correlations were maintained between ctDNA and slide caliper measurement in irradiated subcutaneous tumors (LINE-1, r = .64 and Alu, r = .44, p < .02), and ctDNA and bioluminescence in intratibial tumors (LINE-1, r = .55, p = .018).

CONCLUSIONS

Real-time qPCR of circulating human Alu and LINE-1 DNA provides an accurate measurement of subcutaneous and intratibial xenograft burden that is comparable with conventional bioluminescence imaging and slide caliper measurement. Transient differences in measurements were observed following tumor-targeted IR, but overall all measurements mirrored tumor growth and response.

Abstract 2929: Comparative analysis of circulating human tumor DNA and bioluminescent imaging in monitoring tumor burden and therapeutic response of ionizing radiation in intratibial human prostate tumor xenografts

Purpose/Objective: Pre-clinical models of prostate cancer (PCa) metastases provide critical insight into tumor biology and therapeutic response. Current models require sophisticated reporter transgene models and/or expensive tools to noninvasively monitor tumors in metastatic sites, such as bone. Recent developments in the measurement of circulating tumor DNA (ctDNA) provide an alternative method to noninvasively assess tumor burden at a low cost. Here we present a comparative analysis of human PCa xenograft tumor growth and therapeutic response by simultaneous measurement of ctDNA and bioluminescence.

Materials and methods: Male athymic nude mice were used for intra-tibial (n=10) modeling. LNCaP-CMV-Luc cells were implanted in the tibial medullary canal. Tumor burden was evaluated at pre and post-IR (focal exposure 6 Gy on day 28 post-implantation) time-points by in vivo bioluminescent imaging and quantitative real-time polymerase chain reaction (qPCR) for human LINE1/Alu DNA. qPCR was performed on plasma-derived DNA consecutively on the same day as bioluminescence.

Results: Human genomic DNA quantification was sensitive to 0.1 pg and linear by hAlu (R2=0.98, for 0.1pg-150ng) and LINE DNA (R2=0.99, for 0.1pg-150ng) qPCR. hAlu DNA qPCR produces a much lower Ct value when compared to LINE1; possibly due to its higher copies in the human genome (Ct value 28 versus 22/0.1 pg). Following tumor inoculation, ctDNA level and tumor bioluminescence were strongly and significantly correlated over time (LINE1, r=0.65 and Alu, r=0.59, p&lt;0.002). Following radiation, we observed an immediate (day 32) but transient decrease in the levels of ctDNA and bioluminescence, followed by a gradual increase due to tumor relapse. The correlation between ctDNA level and bioluminescence was not maintained, but responses followed a similar trend.

Conclusions: In the present study, we report that the volume of human PCa xenografts can be accurately measured in the intra-tibial compartments of athymic nude mice by qPCR of circulating human Alu and LINE1 elements. Plasma-derived ctDNA levels highly correlated with tumor bioluminescence over time. Tumor directed radiation therapy exhibited slightly differential responses in ctDNA level and tumor bioluminescence, but overall both measurements followed a similar trend.

Citation Format: Alok Mishra, Kenji Zennami, Esteban Velarde, Jonathan B. Coulter, Srinivasan Yegnasubramanian, Shawn E. Lupold, Theodore L. DeWeese. Comparative analysis of circulating human tumor DNA and bioluminescent imaging in monitoring tumor burden and therapeutic response of ionizing radiation in intratibial human prostate tumor xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2929.

Comparison of Multimodal Therapies and Outcomes Among Patients With High-Risk Prostate Cancer With Adverse Clinicopathologic Features

IMPORTANCE

The optimal management strategy for high-risk prostate cancer and additional adverse clinicopathologic features remains unknown.

OBJECTIVE

To compare clinical outcomes among patients with high-risk prostate cancer after definitive treatment.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study included patients with high-risk prostate cancer (as defined by the National Comprehensive Cancer Network [NCCN]) and at least 1 adverse clinicopathologic feature (defined as any primary Gleason pattern 5 on biopsy, clinical T3b-4 disease, ≥50% cores with biopsy results positive for prostate cancer, or NCCN ≥2 high-risk features) treated between 2000 and 2014 at 16 tertiary centers. Data were analyzed in November 2020.

EXPOSURES

Radical prostatectomy (RP), external beam radiotherapy (EBRT) with androgen deprivation therapy (ADT), or EBRT plus brachytherapy boost (BT) with ADT. Guideline-concordant multimodal treatment was defined as RP with appropriate use of multimodal therapy (optimal RP), EBRT with at least 2 years of ADT (optimal EBRT), or EBRT with BT with at least 1 year ADT (optimal EBRT with BT).

MAIN OUTCOMES AND MEASURES

The primary outcome was prostate cancer-specific mortality; distant metastasis was a secondary outcome. Differences were evaluated using inverse probability of treatment weight-adjusted Fine-Gray competing risk regression models.

RESULTS

A total of 6004 men (median [interquartile range] age, 66.4 [60.9-71.8] years) with high-risk prostate cancer were analyzed, including 3175 patients (52.9%) who underwent RP, 1830 patients (30.5%) who underwent EBRT alone, and 999 patients (16.6%) who underwent EBRT with BT. Compared with RP, treatment with EBRT with BT (subdistribution hazard ratio [sHR] 0.78, [95% CI, 0.63-0.97]; P = .03) or with EBRT alone (sHR, 0.70 [95% CI, 0.53-0.92]; P = .01) was associated with significantly improved prostate cancer-specific mortality; there was no difference in prostate cancer-specific mortality between EBRT with BT and EBRT alone (sHR, 0.89 [95% CI, 0.67-1.18]; P = .43). No significant differences in prostate cancer-specific mortality were found across treatment cohorts among 2940 patients who received guideline-concordant multimodality treatment (eg, optimal EBRT alone vs optimal RP: sHR, 0.76 [95% CI, 0.52-1.09]; P = .14). However, treatment with EBRT alone or EBRT with BT was consistently associated with lower rates of distant metastasis compared with treatment with RP (eg, EBRT vs RP: sHR, 0.50 [95% CI, 0.44-0.58]; P < .001).

CONCLUSIONS AND RELEVANCE

These findings suggest that among patients with high-risk prostate cancer and additional unfavorable clinicopathologic features receiving guideline-concordant multimodal therapy, prostate cancer-specific mortality outcomes were equivalent among those treated with RP, EBRT, and EBRT with BT, although distant metastasis outcomes were more favorable among patients treated with EBRT and EBRT with BT. Optimal multimodality treatment is critical for improving outcomes in patients with high-risk prostate cancer.

Magnetic nanoparticle hyperthermia for treating locally advanced unresectable and borderline resectable pancreatic cancers: the role of tumor size and eddy-current heating

Purpose:

Tumor volume largely determines the success of local control of borderline resectable and locally advanced pancreatic cancer with current therapy. We hypothesized that a tumor-mass normalized dose of magnetic nanoparticle hyperthermia (MNPH) with alternating magnetic fields (AMFs) reduces the effect of tumor volume for treatment.

Methods:

18 female athymic nude mice bearing subcutaneous MiaPaCa02 human xenograft tumors were treated with MNPH following intratumor injections of 5.5 mg Fe/g tumor of an aqueous suspension of magnetic iron-oxide nanoparticles. Mice were randomly divided into control (n = 5) and treated groups having small (0.15 ± 0.03 cm³, n = 4) or large (0.30 ± 0.06 cm³, n = 5) tumors. We assessed the clinical feasibility of this approach and of pulsed AMF to minimize eddy current heating using a finite-element method to solve a bioheat equation for a human-scale multilayer model.

Results:

Compared to the control group, both small and large MiaPaCa02 subcutaneous tumors showed statistically significant growth inhibition. Conversely, there was no significant difference in tumor growth between large and small tumors. Both computational and xenograft models demonstrated higher maximum tumor temperatures for large tumors compared to small tumors. Computational modeling demonstrates that pulsed AMF can minimize nonspecific eddy current heating.

Conclusions:

MNPH provides an advantage to treat large tumors because the MION dose can be adjusted to increase power. Pulsed AMF, with adjusted treatment time, can enhance MNPH in challenging cases such as low MION dose in the target tissue and/or large patients by minimizing nonspecific eddy current heating without sacrificing thermal dose to the target. Nanoparticle heterogeneity in tumors remains a challenge for continued research.

External Validation of the Bone Metastases Ensemble Trees for Survival (BMETS) Machine Learning Model to Predict Survival in Patients With Symptomatic Bone Metastases

PURPOSE

The Bone Metastases Ensemble Trees for Survival (BMETS) model uses a machine learning algorithm to estimate survival time following consultation for palliative radiation therapy for symptomatic bone metastases (SBM). BMETS was developed at a tertiary-care, academic medical center, but its validity and stability when applied to external data sets are unknown.

PATIENTS AND METHODS

Patients treated with palliative radiation therapy for SBM from May 2013 to May 2016 at two hospital-based community radiation oncology clinics were included, and medical records were retrospectively reviewed to collect model covariates and survival time. The Kaplan-Meier method was used to estimate overall survival from consultation to death or last follow-up. Model discrimination was estimated using time-dependent area under the curve (tAUC), which was calculated using survival predictions from BMETS based on the initial training data set.

RESULTS

A total of 216 sites of SBM were treated in 182 patients. Most common histologies were breast (27%), lung (23%), and prostate (23%). Compared with the BMETS training set, the external validation population was older (mean age, 67 v 62 years; P < .001), had more primary breast (27% v 19%; P = .03) and prostate cancer (20% v 12%; P = .01), and survived longer (median, 10.7 v 6.4 months). When the BMETS model was applied to the external data set, tAUC values at 3, 6, and 12 months were 0.82, 0.77, and 0.77, respectively. When refit with data from the combined training and external validation sets, tAUC remained > 0.79.

CONCLUSION

BMETS maintained high discriminative ability when applied to an external validation set and when refit with new data, supporting its generalizability, stability, and the feasibility of dynamic modeling.

Development and Validation of a Clinical Prognostic Stage Group System for Nonmetastatic Prostate Cancer Using Disease-Specific Mortality Results From the International Staging Collaboration for Cancer of the Prostate

Importance

In 2016, the American Joint Committee on Cancer (AJCC) established criteria to evaluate prediction models for staging. No localized prostate cancer models were endorsed by the Precision Medicine Core committee, and 8th edition staging was based on expert consensus.

Objective

To develop and validate a pretreatment clinical prognostic stage group system for nonmetastatic prostate cancer.

Design, Setting, and Participants

This multinational cohort study included 7 centers from the United States, Canada, and Europe, the Shared Equal Access Regional Cancer Hospital (SEARCH) Veterans Affairs Medical Centers collaborative (5 centers), and the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) registry (43 centers) (the STAR-CAP cohort). Patients with cT1-4N0-1M0 prostate adenocarcinoma treated from January 1, 1992, to December 31, 2013 (follow-up completed December 31, 2017). The STAR-CAP cohort was randomly divided into training and validation data sets; statisticians were blinded to the validation data until the model was locked. A Surveillance, Epidemiology, and End Results (SEER) cohort was used as a second validation set. Analysis was performed from January 1, 2018, to November 30, 2019.

Exposures

Curative intent radical prostatectomy (RP) or radiotherapy with or without androgen deprivation therapy.

Main Outcomes and Measures

Prostate cancer-specific mortality (PCSM). Based on a competing-risk regression model, a points-based Score staging system was developed. Model discrimination (C index), calibration, and overall performance were assessed in the validation cohorts.

Results

Of 19 684 patients included in the analysis (median age, 64.0 [interquartile range (IQR), 59.0-70.0] years), 12 421 were treated with RP and 7263 with radiotherapy. Median follow-up was 71.8 (IQR, 34.3-124.3) months; 4078 (20.7%) were followed up for at least 10 years. Age, T category, N category, Gleason grade, pretreatment serum prostate-specific antigen level, and the percentage of positive core biopsy results among biopsies performed were included as variables. In the validation set, predicted 10-year PCSM for the 9 Score groups ranged from 0.3% to 40.0%. The 10-year C index (0.796; 95% CI, 0.760-0.828) exceeded that of the AJCC 8th edition (0.757; 95% CI, 0.719-0.792), which was improved across age, race, and treatment modality and within the SEER validation cohort. The Score system performed similarly to individualized random survival forest and interaction models and outperformed National Comprehensive Cancer Network (NCCN) and Cancer of the Prostate Risk Assessment (CAPRA) risk grouping 3- and 4-tier classification systems (10-year C index for NCCN 3-tier, 0.729; for NCCN 4-tier, 0.746; for Score, 0.794) as well as CAPRA (10-year C index for CAPRA, 0.760; for Score, 0.782).

Conclusions and Relevance

Using a large, diverse international cohort treated with standard curative treatment options, a proposed AJCC-compliant clinical prognostic stage group system for prostate cancer has been developed. This system may allow consistency of reporting and interpretation of results and clinical trial design.

Randomized Phase II Trial of Sipuleucel-T with or without Radium-223 in Men with Bone-metastatic Castration-resistant Prostate Cancer

PURPOSE

To investigate whether radium-223 increases peripheral immune responses to sipuleucel-T in men with bone-predominant, minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

A total of 32 patients were randomized 1:1 in this open-label, phase II multicenter trial. Patients in the control arm received three sipuleucel-T treatments, 2 weeks apart. Those in the combination arm received six doses of radium-223 monthly, with sipuleucel-T intercalated between the second and fourth doses of radium-223. The primary endpoint was a comparison of peripheral antigen PA2024-specific T-cell responses (measured by proliferation index). Secondary endpoints were progression-free survival (PFS), overall survival (OS), and PSA responses.

RESULTS

We enrolled 32 patients, followed for a median of 1.6 years. Six weeks after the first sipuleucel-T dose, participants in the control arm had a 3.2-fold greater change in PA2024-specific T-cell responses compared with those who received combination treatment (P = 0.036). Patients in the combination arm were more likely to have a >50% PSA decline [5 (31%) vs. 0 patients; P = 0.04], and also demonstrated longer PFS [39 vs. 12 weeks; HR, 0.32; 95% confidence interval (CI), 0.14-0.76] and OS (not reached vs. 2.6 years; HR, 0.32; 95% CI, 0.08-1.23).

CONCLUSIONS

Our data raise the possibility of greater clinical activity with the combination of sipuleucel-T and radium-223 in men with asymptomatic bone mCRPC, despite the paradoxically lower immune responses observed. Additional study to confirm these findings in a larger trial is warranted.

Outcomes of Observation vs Stereotactic Ablative Radiation for Oligometastatic Prostate Cancer: The ORIOLE Phase 2 Randomized Clinical Trial

Question

How effectively does stereotactic ablative radiotherapy prevent progression of disease compared with observation in men with recurrent hormone-sensitive prostate cancer with 1 to 3 metastases?

Findings

In this phase 2 randomized clinical trial of 54 men, progression of disease at 6 months occurred in 7 of 36 participants (19%) treated with stereotactic ablative radiotherapy and in 11 of 18 participants (61%) undergoing observation, a statistically significant difference.

Meaning

Stereotactic ablative radiotherapy is a promising treatment approach for men with recurrent hormone-sensitive oligometastatic prostate cancer who wish to delay initiation of androgen deprivation therapy.

Importance

Complete metastatic ablation of oligometastatic prostate cancer may provide an alternative to early initiation of androgen deprivation therapy (ADT).

Objective

To determine if stereotactic ablative radiotherapy (SABR) improves oncologic outcomes in men with oligometastatic prostate cancer.

Design, Setting, and Participants

The Observation vs Stereotactic Ablative Radiation for Oligometastatic Prostate Cancer (ORIOLE) phase 2 randomized study accrued participants from 3 US radiation treatment facilities affiliated with a university hospital from May 2016 to March 2018 with a data cutoff date of May 20, 2019, for analysis. Of 80 men screened, 54 men with recurrent hormone-sensitive prostate cancer and 1 to 3 metastases detectable by conventional imaging who had not received ADT within 6 months of enrollment or 3 or more years total were randomized.

Interventions

Patients were randomized in a 2:1 ratio to receive SABR or observation.

Main Outcomes and Measures

The primary outcome was progression at 6 months by prostate-specific antigen level increase, progression detected by conventional imaging, symptomatic progression, ADT initiation for any reason, or death. Predefined secondary outcomes were toxic effects of SABR, local control at 6 months with SABR, progression-free survival, Brief Pain Inventory (Short Form)–measured quality of life, and concordance between conventional imaging and prostate-specific membrane antigen (PSMA)–targeted positron emission tomography in the identification of metastatic disease.

Results

In the 54 men randomized, the median (range) age was 68 (61-70) years for patients allocated to SABR and 68 (64-76) years for those allocated to observation. Progression at 6 months occurred in 7 of 36 patients (19%) receiving SABR and 11 of 18 patients (61%) undergoing observation (P = .005). Treatment with SABR improved median progression-free survival (not reached vs 5.8 months; hazard ratio, 0.30; 95% CI, 0.11-0.81; P = .002). Total consolidation of PSMA radiotracer-avid disease decreased the risk of new lesions at 6 months (16% vs 63%; P = .006). No toxic effects of grade 3 or greater were observed. T-cell receptor sequencing identified significant increased clonotypic expansion following SABR and correlation between baseline clonality and progression with SABR only (0.082085 vs 0.026051; P = .03).

Conclusions and Relevance

Treatment with SABR for oligometastatic prostate cancer improved outcomes and was enhanced by total consolidation of disease identified by PSMA-targeted positron emission tomography. SABR induced a systemic immune response, and baseline immune phenotype and tumor mutation status may predict the benefit from SABR. These results underline the importance of prospective randomized investigation of the oligometastatic state with integrated imaging and biological correlates.

Trial Registration

ClinicalTrials.gov Identifier: NCT02680587

Design and construction of a Maxwell-type induction coil for magnetic nanoparticle hyperthermia

Purpose: We describe a modified Helmholtz induction coil, or Maxwell coil, that generates alternating magnetic fields (AMF) having field uniformity (≤10%) within a = 3000 cm³ volume of interest for magnetic hyperthermia research.Materials and methods: Two-dimensional finite element analysis (2D-FEA) was used for electromagnetic design of the induction coil set and to develop specifications for the required matching network. The matching network and induction coil set were fabricated using best available practices and connected to a 120 kW industrial induction heating power supply. System performance was evaluated by magnetic field mapping with a magnetic field probe, and tests were performed using gel phantoms.Results: Tests verified that the system generated a target peak AMF amplitude along the coil axis of ∼35 kA/m (peak) at a frequency of 150 ± 10 kHz while maintaining field uniformity to >90% of peak for a volume of ∼3000 cm³.Conclusions: The induction coil apparatus comprising three independent loops, i.e., Maxwell-type improves upon the performance of simple solenoid and Helmholtz coils by providing homogeneous flux density fields within a large volume while minimizing demands on power and stray fields. Experiments with gel phantoms and analytical calculations show that future translational research efforts should be devoted to developing strategies to reduce the impact of nonspecific tissue heating from eddy currents; and, that an inductor producing a homogeneous field has significant clinical potential for deep-tissue magnetic fluid hyperthermia.

Developing an Improved Statistical Approach for Survival Estimation in Bone Metastases Management: The Bone Metastases Ensemble Trees for Survival (BMETS) Model

PURPOSE

To determine whether a machine learning approach optimizes survival estimation for patients with symptomatic bone metastases (SBM), we developed the Bone Metastases Ensemble Trees for Survival (BMETS) to predict survival using 27 prognostic covariates. To establish its relative clinical utility, we compared BMETS with 2 simpler Cox regression models used in this setting.

METHODS AND MATERIALS

For 492 bone sites in 397 patients evaluated for palliative radiation therapy (RT) for SBM from January 2007 to January 2013, data for 27 clinical variables were collected. These covariates and the primary outcome of time from consultation to death were used to build BMETS using random survival forests. We then performed Cox regressions as per 2 validated models: Chow's 3-item (C-3) and Westhoff's 2-item (W-2) tools. Model performance was assessed using cross-validation procedures and measured by time-dependent area under the curve (tAUC) for all 3 models. For temporal validation, a separate data set comprised of 104 bone sites treated in 85 patients in 2018 was used to estimate tAUC from BMETS.

RESULTS

Median survival was 6.4 months. Variable importance was greatest for performance status, blood cell counts, recent systemic therapy type, and receipt of concurrent nonbone palliative RT. tAUC at 3, 6, and 12 months was 0.83, 0.81, and 0.81, respectively, suggesting excellent discrimination of BMETS across postconsultation time points. BMETS outperformed simpler models at each time, with respective tAUC at each time of 0.78, 0.76, and 0.74 for the C-3 model and 0.80, 0.78, and 0.77 for the W-2 model. For the temporal validation set, respective tAUC was similarly high at 0.86, 0.82, and 0.78.

CONCLUSIONS

For patients with SBM, BMETS improved survival predictions versus simpler traditional models. Model performance was maintained when applied to a temporal validation set. To facilitate clinical use, we developed a web platform for data entry and display of BMETS-predicted survival probabilities.

Results of the randomized phase II study of sipuleucel-T (Sip-T) +/- Radium-223 (Ra-223) in men with bone-metastatic castration resistant prostate cancer

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Background: It has been suggested that immune modulation can be augmented by radiation, possibly by enhancing tumor-antigen display. SipT-induced antigen-specific immune responses in mCRPC patients correlate with survival. We hypothesized that the combination of Ra223 and SipT would enhance SipT-related immune response and improve outcomes compared to SipT alone. Methods: Patients with asymptomatic, bone-predominant mCRPC, without visceral mets >1.0 cm, were randomized (1:1) to SipT alone or with 6 doses of Ra223 (NCT02463799). Men in the SipT+Ra223 arm started SipT between the 2nd and 3rd dose of Ra223. The primary immunologic endpoint was PA2024-specific T-cell proliferation 6 wks after the first SipT infusion. Secondary immune endpoints were PA2024-specific ELISPOT response, PAP-specific proliferation and ELISPOT, humoral responses against both antigens, and antigen spread. Clinical endpoints were radiographic PFS, PSA response (≥50% decline), AlkPhos response (≥30% decline), and safety. Results: 32 men were randomized, 16 per arm. Baseline characteristics in SipT+Ra223 and SipT arms were similar: age (median 71 vs. 70 yrs), Gleason (8-10: 69% vs. 69%), baseline PSA (med 25 vs. 33 ng/mL), AlkPhos (med 89 vs. 92 U/L) and ECOG score (≥1: 31% vs. 19%). There was no significant difference in prior use of abi/enza (38% vs. 44%), or chemo (0% vs. 25%). At 6 weeks, absolute PA2024-specific T-cell proliferation was 2.1-fold higher in the Sip-T arm compared to the SipT+Ra223 arm (35.6 vs. 16.6; P=0.03) and remained higher through week 26. Relative to baseline, the 6-week PA2024-specific T-cell proliferation change was 3.6 times greater in the Sip-T arm compared to the SipT+Ra223 arm ( P=0.007) and remained higher through week 14. There were no significant differences in antigen spread or humoral responses. Median radiographic PFS was longer in the SipT+Ra223 arm (9.3 vs. 3.2 months; HR 0.26, 95% CI 0.11–0.61; P=0.007). PSA and AlkPhos responses were better in the SipT+Ra223 arm (PSA50: 5/15=33% vs. 0/14=0%; P=0.04; AlkPhos30: 9/15=60% vs. 1/15=7%; P=0.01). There was no difference in SREs (13% vs. 7%). Conclusions: SipT+Ra223 was associated with improved clinical outcomes and a higher rate of PSA responses compared to SipT alone, although surprisingly, the SipT arm demonstrated higher peripheral PA2024-specific T-cell proliferation. Since neither agent reliably induces PSA responses alone, these data suggest a synergistic effect of the combination. Larger randomized studies of this combination are planned. Clinical trial information: NCT02463799 .

Improvements in Physician Clinical Workflow Measures After Implementation of a Dashboard Program

PURPOSE

To determine whether a combination of data-driven, personalized feedback and implementation of a graduated, sequential intervention model improved key measures of physician workflow and quality in radiation treatment planning.

METHODS AND MATERIALS

All radiation oncologists across 3 facilities at a single academic institution were prospectively evaluated on 5 predefined metrics of timeliness and accuracy in the treatment-planning process using a web-based institutional data repository and an institutional incident learning system. The study period encompassed 10 quarters from 2014 to 2016, with 2013 serving as a retrospective baseline. Physicians received quarterly individualized reports of their compliance metrics (a practice labeled the Physician Dashboard), and administrative interventions were initiated if >20% noncompliance with any metric was exceeded within a quarter. Consecutive quarters of noncompliance resulted in escalating interventions, including progress meetings with department leadership, and culminated in financial penalties. Rates of noncompliance were compared before and after implementation of this model.

RESULTS

Three thousand six hundred sixty pre-Dashboard and 9497 post-Dashboard simulations were analyzed. After Dashboard implementation, significant reductions were observed in the rates of simulation orders requiring signature by a covering physician (14.1% vs 7.4%, P < .001), and the submission of plan contours ≥1 day (43.1% vs 23.1%, P < .001) or ≥2 days (30.8% vs 18.3%, P = .002) after the due date. There was some decrease in rates of inaccurate or incomplete plan submissions (6.2% vs 3.9%, P = .08). Seven of the 12 physicians received at least 1 intervention, with only 2 receiving all levels of intervention.

CONCLUSIONS

Regular assessment and targeted feedback using the Physician Dashboard significantly improved radiation oncologist compliance with clinically meaningful treatment planning responsibilities at a high-volume academic center.

Frequency of Complicated Symptomatic Bone Metastasis Over a Breadth of Operational Definitions

PURPOSE

Numerous randomized trials have demonstrated noninferiority of single- versus multiple-fraction palliative radiation therapy (RT) in the management of uncomplicated bone metastases; yet there is neither a clear definition of what constitutes a complicated lesion, nor substantial data regarding the prevalence of such complicating features in clinical practice. Thus, we identify a range of evidence-based operational definitions of complicated symptomatic bone metastases and characterize the frequency of such complicating features at a high-volume, tertiary care center.

METHODS AND MATERIALS

A retrospective review of patients seen in consultation for symptomatic bone metastases between March 1, 2007, and July 31, 2013, at Johns Hopkins Hospital identified patient and disease characteristics. Descriptive statistics characterized the frequency of the following complicating features: prior RT, prior surgery, neuraxis compromise, pathologic fracture, and soft tissue component at the symptomatic site. A range of definitions for complicated bone metastases was evaluated based on combinations of these features. Uni- and multivariable logistic regressions evaluated the odds of complicated bone metastases as a function of site of primary cancer and of the symptomatic target lesion.

RESULTS

A total of 686 symptomatic bone metastases in 401 patients were evaluated. Percent of target sites complicated by prior RT was 4.4%, prior surgery was 8.9%, pathologic fracture was 20.6%, neuraxis compromise was 52.0% among spine and medial pelvis sites, and soft tissue component was 38.6%. More than 96 possible definitions of complicated bone metastases were identified. The presence of such complicated lesions ranged from 2.3% to 67.3%, depending on the operational definition used. Odds of a complicated lesion were significantly higher for spine sites and select nonbreast histologies.

CONCLUSIONS

In this retrospective study, we found complicated symptomatic bone metastases may be present in up to two-thirds of patients. Literature review also demonstrates no clear standard definition of complicated bone metastases, potentially explaining underutilization of single-fraction palliative RT in this setting.

Randomized phase II study of sipuleucel-T (SipT) with or without radium-223 (Ra223) in men with asymptomatic bone-metastatic castrate-resistant prostate cancer (mCRPC)

130

Background: SipT-induced antigen-specific immune responses in mCRPC patients correlate with survival. Due to the immunomodulatory effects of radiopharmaceutical agents (e.g. enhancing tumor-antigen display), we hypothesized that combined use of Ra223 and SipT would augment SipT-related immune response and improve outcomes compared to SipT alone. Methods: Patients with asymptomatic mCRPC and bone-predominant mets, without visceral mets >1.0 cm, were randomized (1:1) to standard SipT alone or combined with 6 doses of Ra223 (NCT02463799). Men in the SipT+Ra223 arm received SipT between the 2nd and 3rd dose of Ra223. Clinical endpoints were radiographic/clinical PFS, PSA response (≥50% decline), AlkPhos response (≥30% decline), and safety. Immunologic endpoints were PA2024-specific T-cell proliferation 6 wks after the first SipT infusion, PA2024-specific ELISPOT response, PAP-specific proliferation and ELISPOT, humoral responses against both antigens, and antigen spread. Results: 32 men were randomized, 16 per arm. Baseline characteristics in SipT and SipT+Ra223 arms were matched with respect to age (median 70 vs 71 yrs), Gleason (8-10: 69% vs 69%), PSA (median 82 vs 72 ng/mL), AlkPhos (median 125 vs 125 U/L) and ECOG scores (≥1: 19% vs 31%). After median follow up of 5.3 (range 2.8–26.6) mo, median PFS was longer in the SipT+Ra223 arm (10.7 vs 3.1 mo; HR 0.35, 95% CI 0.15–0.81; P=0.02). Outcomes were also better in the SipT+Ra223 arm with respect to PSA responses (5/15=33% vs 0/14=0%; P=0.04) and AlkPhos responses (9/15=60% vs 1/15=7%; P=0.01). No safety concerns were observed with the combination (grade 3 AEs shown in the Table). Conclusions: SipT combined with Ra223 was associated with improved clinical outcomes compared to SipT alone. Since neither agent reliably induces PSA responses alone, these data suggest a synergistic effect of the combination. Immunologic endpoints will be presented at the meeting. Larger randomized studies of this combination are warranted. Clinical trial information: NCT02463799. [Table: see text]

Testosterone recovery as biomarker for overall and cause-specific survival in combined treated patients with high-risk and locally advanced prostate cancer

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Background: Androgen deprivation therapy (ADT) can cause considerable toxicity and may influence outcome. The study assessed the impact of testosterone recovery (TR) on survival after ADT and definitive radiotherapy in two independent cohorts. Methods: Two hundred and forty-four patients (high risk JHH cohort N=106, T1c-T3N0M0 [A], locally advanced OUH cohort N=138, T1c-T4N0-1M0 [B]) with adenocarcinoma of the prostate were included in this retrospective analysis. Short and long-term ADT was given (median 12 months A, 24 months B, respectively,) and along with conformal external beam radiation 76-80 Gy given to the prostate in cohort A, 74 Gy prescribed in cohort B and 46-50 Gy to the whole pelvis. Testosterone levels were measured at the end of ADT and at biochemical relapse. TR was defined as ≥ 9 nmol/L. Kaplan Meier plots were generated for overall survival (OS) and cause-specific survival (CSS) stratified by TR, in addition to patient characteristics median time to TR and FU were calculated. Results: The median age in the A cohort was 66.7 years and 64.7 years in the B group. FU was 6 years for A and 8 years in B. Patients in group A received median ADT of 12 months and 24 months in group B. The median time to TR was 1.6 yr in A and 2.5 yrs in B, respectively. Patients in group A stratified to TR showed no difference in overall survival (p=0.92)), on contrary, patients in group B showed improved overall survival depending on TR (Fig. 1, KM plot, 10 year OS 75.3% vs 59.9% p=0.034). CSS was seemed to trend towards improvement with TR for cohort A (p=0.19) and was improved in cohort B (p=0.022). The Univariate ADT length, age, and RT dose was associated with time to TR, but on multivariate analysis only longer ADT time (p = 0.03) was significantly associated with time to TR. Conclusions: TR was associated with improved OS in patients with unfavorable locally advanced disease a finding not seen in patients with high-risk disease.

PSA status after neoadjuvant androgen deprivation therapy before high-dose-rate brachytherapy as biomarker for prediction of long-term outcome in high-risk prostate cancer patients

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Background: The aim is to investigate the clinical significance of biochemical response after Androgen Deprivation Therapy (ADT) prior to high-dose-rate brachytherapy (HDR-BT) for early identification of patients at increased risk of recurrence. Measured outcomes included biochemical relapse free survival (bRFS), distant metastasis free survival (DMFS) and overall survival (OS). Methods: A total of 324 patients with high-risk Prostate Cancer (PCa) were identified in the Norwegian Radium Hospital brachytherapy database. Neo-adjuvant ADT was administered for 3-6 months, followed by two 10 Gy HDR-BT treatments to the prostate, each spaced by two weeks, followed by conformal external beam radiation to 50 Gy to the prostate gland and seminal vesicles. Total length of ADT ranged from 12 to 36 months. PSA (ng/mL) and testosterone values (T, nmol/L) after 3-6 months of neo-adjuvant ADT were measured. Kaplan Meier and Cox regression analyses were performed. Results: Median age at diagnosis was 66 years and median follow-up was 10 years. At last follow-up, 277 patients (85,2%) were alive, 10 patients (3.1%) had died of prostate cancer and 37 patients (11.4%) died of other causes. 24 patients (7.4%) had biochemical relapse and 9 patients (2.8%) had distant metastasis within the first 5 years. Patients with PSA > 1 after neo-adjuvant therapy had 4.3 (95%CI 1.7 to 11.1) higher odds of biochemical relapse within 5 years compared to patients with PSA < 1 (p = 0.002). ROC analysis confirmed that PSA < 1 had a prediction accuracy of 0.76 (sensitivity 68% and specificity 67%). T < 0.7 and PSA < 1 after neo-adjuvant therapy were associated with improved bRFS, DMFS and OS (p < 0.001). Neither the length of neo-adjuvant nor total ADT treatment impacted outcomes (p > 0.05). Conclusions: Dose intensification with 2 HDR-BT boosts resulted in excellent survival in our cohort. PSA > 1 after neo-adjuvant ADT may be able to predict patients at increased risk of relapse and worse OS and identify patients in whom increased monitoring and/or intervention is warranted. ADT > 1 year did not improve outcome, indicating that shorter course of ADT may be used.

A phase II randomized trial of Observation versus stereotactic ablative RadiatIon for OLigometastatic prostate CancEr (ORIOLE)

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Background: Mounting evidence supports metastatic ablation for oligometastatic prostate cancer (OMPC). Importantly, biomarkers to determine patients who benefit most from complete ablation are unknown. We hypothesize that stereotactic ablative radiation (SABR) will improve oncologic outcomes in men with OMPC. Methods: In this phase II randomized trial, men with recurrent hormone-sensitive OMPC (1-3 radiation fields) were stratified by primary management (radiotherapy vs surgery), PSA doubling time, and prior androgen deprivation therapy and randomized 2:1 to SABR or observation (OBS). The primary endpoint was progression at 6 months by PSA (≥ 25% increase and ≥ nadir + 2 ng/mL), conventional imaging (RECIST 1.1 criteria or new lesion on bone scan), or symptomatic decline. Tissue, liquid and imaging correlatives were analyzed as biomarkers. Results: From 5/2016-3/2018, 54 patients were randomized. Progression at six months occurred in 19% of SABR patients and 61% of observation patients [p=0.005]. SABR improved median PFS (not reached vs 5.8 months, HR 0.30, p = 0.0023). Total consolidation of PSMA radiotracer-avid disease decreased the risk of new lesions at six months (16% vs 63%, p = 0.006). No toxicity ≥ grade 3 was observed. T-cell receptor sequencing identified increased clonotypic expansion (p = 0.03) following SABR and correlation between baseline clonality and progression with SABR only. Analysis of circulating tumor DNA (ctDNA) and germline mutations identified a mutation profile that was associated with benefit from SABR. Conclusions: SABR for OMPC improves outcomes and is enhanced by total consolidation of disease identified by PSMA-targeted PET. SABR induces a systemic immune response, and baseline immune phenotype and tumor mutation status may predict the benefit from SABR. These results underline the importance of prospective randomized investigation of the oligometastatic state with integrated imaging and biological correlates. Clinical trial information: NCT02680587.

Analysis of Spatial Dose-Volume Relationships and Decline in Sexual Function Following Permanent Brachytherapy for Prostate Cancer

OBJECTIVE

To explore relationships between dose to periprostatic anatomic structures and erectile dysfunction (ED) outcomes in an institutional cohort treated with prostate brachytherapy.

METHODS

The Sexual Health Inventory for Men (SHIM) instrument was administered for stage cT1-T2 prostate cancer patients treated with Pd-103 brachytherapy over a 10-year interval. Dose volume histograms for regional organs at risk and periprostatic regions were calculated with and without expansions to account for contouring uncertainty. Regression tree analysis clustered patients into ED risk groups.

RESULTS

We identified 115 men treated with definitive prostate brachytherapy who had 2 years of complete follow-up. On univariate analysis, the subapical region (SAR) caudal to prostate was the only defined region with dose volume histograms parameters significant for potency outcomes. Regression tree analysis separated patients into low ED risk (mean 2-year SHIM 20.03), medium ED risk (15.02), and high ED risk (5.54) groups. Among patients with good baseline function (SHIM ≥ 17), a dose ≥72.75 Gy to 20% of the SAR with 1 cm expansion was most predictive for 2-year potency outcome. On multivariate analysis, regression tree risk group remained significant for predicting potency outcomes even after adjustment for baseline SHIM and age.

CONCLUSION

Dose to the SAR immediately caudal to prostate was predictive for potency outcomes in patients with good baseline function. Minimization of dose to this region may improve potency outcomes following prostate brachytherapy.

A phase II randomized placebo-controlled double-blind study of salvage radiation therapy plus placebo versus SRT plus enzalutamide with high-risk PSA-recurrent prostate cancer after radical prostatectomy (SALV-ENZA)

BACKGROUND

In men with a rising PSA following radical prostatectomy, salvage radiation therapy (SRT) offers a second chance for cure. Hormonal therapy can be combined with SRT in order to increase prostate tumor control, albeit with associated higher rates of treatment side effects. This trial studies the effectiveness of SRT combined with hormonal therapy using a more potent anti-androgen with a favorable side effect profile. Enzalutamide, a next generation selective androgen receptor antagonist, is approved by the Food and Drug Administration for the treatment of metastatic castrate-resistant prostate cancer (CRPC) where it has been shown to improve overall survival in combination with androgen deprivation therapy. The primary objective of this study is to evaluate the efficacy of combination SRT and enzalutamide for freedom-from-PSA-progression. Secondary objectives include time to local recurrence within the radiation field, metastasis-free survival and safety as determined by frequency and severity of adverse events.

METHODS/DESIGN

This is a randomized, double-blind, phase II, prospective, multicenter study in adult males with biochemically recurrent prostate cancer following radical prostatectomy. Following registration, enzalutamide 160 mg or placebo by mouth (PO) once daily will be administered for 6 months. Following two months of study drug, external beam radiotherapy to 66.6-70.2 Gray (Gy) will be administered to the prostate bed over 7-8 weeks while continuing daily placebo/enzalutamide. This is followed by two additional months of placebo/enzalutamide.

DISCUSSION

The SALV-ENZA trial is the first phase II placebo-controlled double-blinded randomized study to test SRT in combination with a next generation androgen receptor antagonist in men with high-risk recurrent prostate cancer after radical prostatectomy. The primary hypothesis of this study is that clinical outcomes will be improved by the addition of enzalutamide compared to standard-of-care SRT alone and pave the path for phase III evaluation of this combination.

TRIAL REGISTRATIONS

ClinicaltTrials.gov Identifier: NCT02203695 Date of Registration: 06/16/2014. Date of First Participant Enrollment: 04/16/2015.