Non-Contact Irreversible Electroporation in the Esophagus With a Wet Electrode Approach

Our objective was to develop a technique for performing irreversible electroporation (IRE) of esophageal tumors while mitigating thermal damage to the healthy lumen wall. We investigated noncontact IRE using a wet electrode approach for tumor ablation in a human esophagus with finite element models for electric field distribution, joule heating, thermal flux, and metabolic heat generation. Simulation results indicated the feasibility of tumor ablation in the esophagus using an catheter mounted electrode immersed in diluted saline. The ablation size was clinically relevant, with substantially lesser thermal damage to the healthy esophageal wall when compared to IRE performed by placing a monopolar electrode directly into the tumor. Additional simulations were used to estimate ablation size and penetration during noncontact wet-electrode IRE (wIRE) in the healthy swine esophagus. A novel catheter electrode was manufactured and wIRE evaluated in seven pigs. wIRE was performed by securing the device in the esophagus and using diluted saline to isolate the electrode from the esophageal wall while providing electric contact. Computed tomography and fluoroscopy were performed post-treatment to document acute lumen patency. Animals were sacrificed within four hours following treatment for histologic analysis of the treated esophagus. The procedure was safely completed in all animals; post-treatment imaging revealed intact esophageal lumen. The ablations were visually distinct on gross pathology, demonstrating full thickness, circumferential regions of cell death (3.52 ± 0.89 mm depth). Acute histologic changes were not evident in nerves or extracellular matrix architecture within the treatment site. Catheter directed noncontact IRE is feasible for performing penetrative ablations in the esophagus while avoiding thermal damage.

Patient Radiation Doses in IR Procedures: The American College of Radiology Dose Index Registry-Fluoroscopy Pilot

PURPOSE

To update normative data on fluoroscopy dose indices in the United States for the first time since the Radiation Doses in Interventional Radiology study in the late 1990s.

MATERIALS AND METHODS

The Dose Index Registry-Fluoroscopy pilot study collected data from March 2018 through December 2019, with 50 fluoroscopes from 10 sites submitting data. Primary radiation dose indices including fluoroscopy time (FT), cumulative air kerma (Ka,r), and kerma area product (PKA) were collected for interventional radiology fluoroscopically guided interventional (FGI) procedures. Clinical facility procedure names were mapped to the American College of Radiology (ACR) common procedure lexicon. Distribution parameters including the 10th, 25th, 50th, 75th, 95th, and 99th percentiles were computed.

RESULTS

Dose indices were collected for 70,377 FGI procedures, with 50,501 ultimately eligible for analysis. Distribution parameters are reported for 100 ACR Common IDs. FT in minutes, Ka,r in mGy, and PKA in Gy-cm2 are reported in this study as (n; median) for select ACR Common IDs: inferior vena cava filter insertion (1,726; FT: 2.9; Ka,r: 55.8; PKA: 14.19); inferior vena cava filter removal (464; FT: 5.7; Ka,r: 178.6; PKA: 34.73); nephrostomy placement (2,037; FT: 4.1; Ka,r: 39.2; PKA: 6.61); percutaneous biliary drainage (952; FT: 12.4; Ka,r: 160.5; PKA: 21.32); gastrostomy placement (1,643; FT: 3.2; Ka,r: 29.1; PKA: 7.29); and transjugular intrahepatic portosystemic shunt placement (327; FT: 34.8; Ka,r: 813.0; PKA: 181.47).

CONCLUSIONS

The ACR DIR-Fluoro pilot has provided state-of-the-practice statistics for radiation dose indices from IR FGI procedures. These data can be used to prioritize procedures for radiation optimization, as demonstrated in this work.

Evaluation of an Integrated Spectroscopy and Classification Platform for Point-of-Care Core Needle Biopsy Assessment: Performance Characteristics from Ex Vivo Renal Mass Biopsies

PURPOSE

To evaluate a transmission optical spectroscopy instrument for rapid ex vivo assessment of core needle cancer biopsies (CNBs) at the point of care.

MATERIALS AND METHODS

CNBs from surgically resected renal tumors and nontumor regions were scanned on their sampling trays with a custom spectroscopy instrument. After extracting principal spectral components, machine learning was used to train logistic regression, support vector machines, and random decision forest (RF) classifiers on 80% of randomized and stratified data. The algorithms were evaluated on the remaining 20% of the data set held out during training. Binary classification (tumor/nontumor) was performed based on a decision threshold. Multinomial classification was also performed to differentiate between the subtypes of renal cell carcinoma (RCC) and account for potential confounding effects from fat, blood, and necrotic tissue. Classifiers were compared based on sensitivity, specificity, and positive predictive value (PPV) relative to a histopathologic standard.

RESULTS

A total of 545 CNBs from 102 patients were analyzed, yielding 5,583 spectra after outlier exclusion. At the individual spectra level, the best performing algorithm was RF with sensitivities of 96% and 92% and specificities of 90% and 89%, for the binary and multiclass analyses, respectively. At the full CNB level, RF algorithm also showed the highest sensitivity and specificity (93% and 91%, respectively). For RCC subtypes, the highest sensitivity and PPV were attained for clear cell (93.5%) and chromophobe (98.2%) subtypes, respectively.

CONCLUSIONS

Ex vivo spectroscopy imaging paired with machine learning can accurately characterize renal mass CNB at the time of tissue acquisition.

Patient Radiation Doses in Interventional Radiology Procedures: Comparison of fluoroscopy dose indices from the American College of Radiology Dose Index Registry-Fluoroscopy (DIR-Fluoro) Pilot to the RAD-IR study

PURPOSE

To compare interventional radiology fluoroscopically-guided intervention (FGI) radiation dose index distributions from the American College of Radiology (ACR) Fluoroscopy Dose Index Registry (DIR-Fluoro) pilot to the Radiation Doses in Interventional Radiology (RAD-IR) study.

MATERIALS AND METHODS

Individual and grouped ACR Common IDs (procedure types) from the DIR-Fluoro pilot were matched to procedure types in the RAD-IR study. Fifteen comparisons were made. Distribution parameters including the 10^th, 25^th, 50^th, 75^th, and 95^th percentiles were compared for fluoroscopy time (FT), cumulative air kerma (K_a,r), and kerma area product (P_KA). Two derived indices were computed using median dose indices. The procedure-averaged reference air kerma rate (K_a,r¯) was computed as K_a,r / FT. The procedure-averaged X-ray field size at the reference point (A_r¯) was computed as P_KA / (K_a,r * 1,000).

RESULTS

Median FT was equally likely to be higher or lower in the DIR-Fluoro pilot compared to RAD-IR, while maximum FT was almost twice as likely to be higher in DIR-Fluoro than RAD-IR. Median K_a,r was lower in the DIR-Fluoro pilot for all procedures, as was median P_KA. The maximum K_a,r and P_KA were more often higher in the DIR-Fluoro pilot compared to RAD-IR. K_a,r¯ followed the same pattern as K_a,r, while A_r¯ was often greater in DIR-Fluoro.

CONCLUSIONS

Median dose indices have decreased since the RAD-IR study. Typical K_a,r rates are lower, a result of the use of lower default dose rates. However, opportunities for quality improvement exist, including a renewed focus on tight collimation of the imaging field of view.

The Impact of PIK3R1 Mutations and Insulin-PI3K-Glycolytic Pathway Regulation in Prostate Cancer

PURPOSE

Oncogenic alterations of the PI3K/AKT pathway occur in >40% of patients with metastatic castration-resistant prostate cancer, predominantly via PTEN loss. The significance of other PI3K pathway components in prostate cancer is largely unknown.

EXPERIMENTAL DESIGN

Patients in this study underwent tumor sequencing using the MSK-IMPACT clinical assay to capture single-nucleotide variants, insertions, and deletions; copy-number alterations; and structural rearrangements, or were profiled through The Cancer Genome Atlas. The association between PIK3R1 alteration/expression and survival was evaluated using univariable and multivariable Cox proportional-hazards regression models. We used the siRNA-based knockdown of PIK3R1 for functional studies. FDG-PET/CT examinations were performed with a hybrid positron emission tomography (PET)/CT scanner for some prostate cancer patients in the MSK-IMPACT cohort.

RESULTS

Analyzing 1,417 human prostate cancers, we found a significant enrichment of PIK3R1 alterations in metastatic cancers compared with primary cancers. PIK3R1 alterations or reduced mRNA expression tended to be associated with worse clinical outcomes in prostate cancer, particularly in primary disease, as well as in breast, gastric, and several other cancers. In prostate cancer cell lines, PIK3R1 knockdown resulted in increased cell proliferation and AKT activity, including insulin-stimulated AKT activity. In cell lines and organoids, PIK3R1 loss/mutation was associated with increased sensitivity to AKT inhibitors. PIK3R1-altered patient prostate tumors had increased uptake of the glucose analogue 18F-fluorodeoxyglucose in PET imaging, suggesting increased glycolysis.

CONCLUSIONS

Our findings describe a novel genomic feature in metastatic prostate cancer and suggest that PIK3R1 alteration may be a key event for insulin-PI3K-glycolytic pathway regulation in prostate cancer.

MRI-guided focused ultrasound focal therapy for patients with intermediate-risk prostate cancer: a phase 2b, multicentre study

BACKGROUND

Men with grade group 2 or 3 prostate cancer are often considered ineligible for active surveillance; some patients with grade group 2 prostate cancer who are managed with active surveillance will have early disease progression requiring radical therapy. This study aimed to investigate whether MRI-guided focused ultrasound focal therapy can safely reduce treatment burden for patients with localised grade group 2 or 3 intermediate-risk prostate cancer.

METHODS

In this single-arm, multicentre, phase 2b study conducted at eight health-care centres in the USA, we recruited men aged 50 years and older with unilateral, MRI-visible, primary, intermediate-risk, previously untreated prostate adenocarcinoma (prostate-specific antigen ≤20 ng/mL, grade group 2 or 3; tumour classification ≤T2) confirmed on combined biopsy (combining MRI-targeted and systematic biopsies). MRI-guided focused ultrasound energy, sequentially titrated to temperatures sufficient for tissue ablation (about 60-70°C), was delivered to the index lesion and a planned margin of 5 mm or more of normal tissue, using real-time magnetic resonance thermometry for intraoperative monitoring. Co-primary outcomes were oncological outcomes (absence of grade group 2 and higher cancer in the treated area at 6-month and 24-month combined biopsy; when 24-month biopsy data were not available and grade group 2 or higher cancer had occurred in the treated area at 6 months, the 6-month biopsy results were included in the final analysis) and safety (adverse events up to 24 months) in all patients enrolled in the study. This study is registered with ClinicalTrials.gov, NCT01657942, and is no longer recruiting.

FINDINGS

Between May 4, 2017, and Dec 21, 2018, we assessed 194 patients for eligibility and treated 101 patients with MRI-guided focused ultrasound. Median age was 63 years (IQR 58-67) and median concentration of prostate-specific antigen was 5·7 ng/mL (IQR 4·2-7·5). Most cancers were grade group 2 (79 [78%] of 101). At 24 months, 78 (88% [95% CI 79-94]) of 89 men had no evidence of grade group 2 or higher prostate cancer in the treated area. No grade 4 or grade 5 treatment-related adverse events were reported, and only one grade 3 adverse event (urinary tract infection) was reported. There were no treatment-related deaths.

INTERPRETATION

24-month biopsy outcomes show that MRI-guided focused ultrasound focal therapy is safe and effectively treats grade group 2 or 3 prostate cancer. These results support focal therapy for select patients and its use in comparative trials to determine if a tissue-preserving approach is effective in delaying or eliminating the need for radical whole-gland treatment in the long term.

FUNDING

Insightec and the National Cancer Institute.

Phase II Study of Neoadjuvant Nivolumab in Patients with Locally Advanced Clear Cell Renal Cell Carcinoma Undergoing Nephrectomy

Immune checkpoint inhibitor therapy improves survival in patients with metastatic renal cell carcinoma (RCC) but has not been studied well preoperatively in patients with localized disease undergoing nephrectomy. We conducted a single-center study to evaluate the safety and feasibility of neoadjuvant nivolumab in patients undergoing nephrectomy for localized RCC. Eligible patients had a >20% risk of recurrence, as estimated by a preoperative nomogram. Patients received nivolumab every 2 wk for four treatments prior to surgery. The primary endpoints were feasibility, defined as completing at least three treatments without significant surgical delay, and safety, defined as the rate of surgical complications. Treatment effects were assessed by radiomics and immunohistochemistry. A total of 18 patients (11 men; median age 60 yr) with clear cell RCC were enrolled. All received at least one dose of nivolumab and proceeded to nephrectomy without delay; 16/18 patients completed all four doses. Two patients discontinued nivolumab for immune-related adverse events, and four had surgical complications as per the Clavien-Dindo classification. Integrated pathology plus radiomic analysis demonstrated an association between post-treatment immune infiltration and low entropy apparent diffusion coefficient on magnetic resonance imaging. Nivolumab prior to nephrectomy was safe and feasible, without significant surgical delays and with an expected rate of immune-related adverse events. PATIENT SUMMARY: We evaluated the outcomes for patients with localized kidney cancer who received immunotherapy prior to surgery to remove their kidney tumor. In a small group of patients who had cancer confined to the kidney, this approach appeared safe and feasible.

A Tale of Two Pulmonary Artery Catheters

Innovative catheter-based therapies are increasingly being used for the treatment of patients with submassive pulmonary embolism. These patients may be monitored in the intensive care unit following insertion of specialized pulmonary artery catheters. However, the infusion catheters utilized in catheter-based therapies differ greatly from traditional pulmonary artery catheters designed for hemodynamic monitoring. As such, the critical care team will have to be familiar with the monitoring and management of these novel catheters. Important distinctions between the catheters are illustrated using a clinical case report.

Prevalence and Landscape of Actionable Genomic Alterations in Renal Cell Carcinoma

PURPOSE

We report our experience with next-generation sequencing to characterize the landscape of actionable genomic alterations in renal cell carcinoma (RCC).

EXPERIMENTAL DESIGN

A query of our institutional clinical sequencing database (MSK-IMPACT) was performed that included tumor samples from 38,468 individuals across all cancer types. Somatic variations were annotated using a precision knowledge database (OncoKB) and the available clinical data stratified by level of evidence. Alterations associated with response to immune-checkpoint blockade (ICB) were analyzed separately; these included DNA mismatch repair (MMR) gene alterations, tumor mutational burden (TMB), and microsatellite instability (MSI). Data from The Cancer Genome Atlas (TCGA) consortium as well as public data from several clinical trials in metastatic RCC were used for validation purposes. Multiregional sequencing data from the TRAcking Cancer Evolution through Therapy (TRACERx) RENAL cohort were used to assess the clonality of somatic mutations.

RESULTS

Of the 753 individuals with RCC identified in the MSK-IMPACT cohort, 115 showed evidence of targetable alterations, which represented a prevalence of 15.3% [95% confidence interval (CI), 12.7%-17.8%). When stratified by levels of evidence, the alterations identified corresponded to levels 2 (11.3%), 3A (5.2%), and 3B (83.5%). A low prevalence was recapitulated in the TCGA cohort at 9.1% (95% CI, 6.9%-11.2%). Copy-number variations predominated in papillary RCC tumors, largely due to amplifications in the MET gene. Notably, higher rates of actionability were found in individuals with metastatic disease (stage IV) compared with those with localized disease (OR, 2.50; 95% CI, 1.16-6.16; Fisher's P = 0.01). On the other hand, the prevalence of alterations associated with response to ICB therapy was found to be approximately 5% in both the MSK-IMPACT and TCGA cohorts and no associations with disease stage were identified (OR, 1.35; 95% CI, 0.46-5.40; P = 0.8). Finally, multiregional sequencing revealed that the vast majority of actionable mutations occurred later during tumor evolution and were only present subclonally in RCC tumors.

CONCLUSIONS

RCC harbors a low prevalence of clinically actionable alterations compared with other tumors and the evidence supporting their clinical use is limited. These aberrations were found to be more common in advanced disease and seem to occur later during tumor evolution. Our study provides new insights on the role of targeted therapies for RCC and highlights the need for additional research to improve treatment selection using genomic profiling.

A prospective phase 2/3 study of PSMA-targeted 18F-DCFPyL-PET/CT in patients (pts) with prostate cancer (PCa) (OSPREY): A sub-analysis of disease staging changes in PCa pts with recurrence or metastases on conventional imaging

e17003

Background: Conventional imaging and bone scintigraphy are suboptimal modalities for identifying PCa. PSMA-based imaging is highly promising for PCa detection. 18F-DCFPyL is a novel PSMA-targeted radiopharmaceutical for positron emission tomography (PET) that may be useful in staging of PCa. The diagnostic performance, detection rate, and potential impact of 18F-DCFPyL on staging of pts with high-risk PCa have been previously reported. Here we report on the impact of 18F-DCFPyL on staging of pts with PCa recurrence or metastases on conventional imaging. Methods: 18F-DCFPyL-PET/CT was evaluated in 117 men with radiologic evidence of local recurrence or metastatic disease on baseline anatomical imaging (CT, MRI) or whole-body bone scintigraphy and in whom at least one lesion was deemed amenable to biopsy. A single dose of 9 mCi (333 MBq) of 18F-DCFPyL was administered via intravenous injection, followed by PET/CT acquisition 1 to 2 hours thereafter. Based on TNM staging: prostatic (T), pelvic LN (N), extra-pelvic LN (M1a), bone (M1b) and other visceral organs/soft tissue (M1c), 18F-DCFPyL-PET/CT detection rates including lesion counts were systematically analyzed. Three central, blinded, and independent readers evaluated the 18F-DCFPyL scans. Results: In this study, 82 (70%) patients had baseline radiographic M1 stage disease (14 patients with M1a, 50 patients with M1b, 18 patients with M1c) and 33 (28%) patients were M0 stage at baseline by central conventional imaging review; two patients were unevaluable. 18F-DCFPyL-PET/CT up-staged 58% (19/33) of pts from M0 to M1, of whom 91% (10/11) who underwent an extra-pelvic biopsy were confirmed to have M1 disease by pathology, including 9 patients with M1b and 1 patient with M1a. Of the patients who were staged M1 at baseline, 18F-DCFPyL-PET/CT upstaged 16% (10/64; M1a to M1b or M1c: n = 4; M1b to M1c: n = 6) of pts to a higher M1 sub-stage and down-staged 22% (18/82) to M0. Conclusions: 18F-DCFPyL-PET/CT identified M1 disease in the majority of patients examined who otherwise had locoregional disease. These data suggest that 18F-DCFPyL-PET/CT may be a useful tool in properly staging men with both metastatic and nonmetastatic relapsed disease, which could lead to superior treatment paradigms than currently exist using conventional imaging. Clinical trial information: NCT02981368.

A pilot study of preoperative nivolumab in high-risk nonmetastatic renal cell carcinoma

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Background: Immunotherapy improves survival in patients with advanced renal cell carcinoma (RCC), but has no established role for perioperative use in patients with localized RCC. Neoadjuvant immunotherapy is a promising strategy in several cancers, and may leverage the primary tumor as antigen source. Methods: We conducted a single institution pilot study of neoadjuvant nivolumab in patients with RCC undergoing nephrectomy with curative intent. Patients were eligible if their risk of metastatic recurrence within the first 12 years was >20% by an established nomogram. After confirmatory biopsy and renal MRI, patients were treated with standard dose nivolumab every 2 weeks for 4 treatments, with a follow-up renal MRI prior to nephrectomy. The primary end points of the study were safety and feasibility defined as being able to complete 3/4 treatments without surgical delay. We evaluated adverse events by CTCAE, surgical safety by Clavien-Dindo classification, and tumor radiographic response by RECIST 1.1. Results: Eighteen (11 men, 7 women; median age 60) were enrolled. All patients had clear cell RCC, median tumor size at baseline was 8.8cm (range 6.4-14.2cm). Median predicted 12-year probability of recurrence was 45% (range 25-71%). All received at least 1 dose of nivolumab; 16/18 patients completed all 4 doses. 17/18 (94%) patients completed at least 3 doses. No patient had notable delay in the timing of their nephrectomy. 4 patients had surgical complications per Clavien-Dindo classification, including 2 with grade 3a chylous ascites after lymphadenectomy. Two patients had nivolumab discontinued for immune-related adverse events, including grade 3 transaminitis and grade 2 arthralgias; a third patient developed grade 4 colitis 4 months after completing nivolumab. All patients had stable disease as the best response prior to surgery. Recurrence-free survival at 2 years was 0.74 (95%CI 0.45-0.90). We analyzed an additional 21 patients with metastatic RCC (20 ccRCC, 1 epithelioid AML) who subsequently had nephrectomy after standard immunotherapy. 15 patients had received ipilimumab+nivolumab, 6 received single-agent PD-1 or PD-L1 inhibitors. 3 (14%) patients achieved a near or complete pathologic response, including a patient with epithelioid AML. Analysis of radiologic and pathologic biomarkers of response are ongoing and will be presented at conference. Conclusions: In this pilot study, there were no new safety signals or delays in surgery with preoperative nivolumab. Neoadjuvant immunotherapy shows preliminary evidence of safety, feasibility and efficacy; biomarker studies may help identify individuals who may have a higher likelihood of response. Clinical trial information: NCT02595918 .

A prospective phase II/III study of PSMA-targeted 18F-DCFPyL-PET/CT in patients (pts) with prostate cancer (PCa) (OSPREY): A subanalysis of disease staging changes in PCa pts with recurrence or metastases on conventional imaging

32

Background: Conventional imaging and bone scintigraphy are suboptimal modalities for identifying PCa. PSMA-based imaging is highly promising for PCa detection. 18F-DCFPyL is a novel PSMA-targeted radiopharmaceutical for positron emission tomography (PET) that may be useful in staging of PCa. The diagnostic performance, detection rate, and potential impact of 18F-DCFPyL on staging of pts with high- risk PCa have been previously reported. Here we report on the impact of 18F-DCFPyL on staging of pts with PCa recurrence or metastases on conventional imaging. Methods: 18F-DCFPyL-PET/CT was evaluated in 117 men with radiologic evidence of local recurrence or metastatic disease on baseline anatomical imaging (CT, MRI) or whole-body bone scintigraphy and in whom at least one lesion was deemed amenable to biopsy. A single dose of 9 mCi (333 MBq) of 18F-DCFPyL was administered via intravenous injection, followed by PET/CT acquisition 1 to 2 hours thereafter. Based on TNM staging: prostatic (T), pelvic LN (N), extra-pelvic LN (M1a), bone (M1b) and other visceral organs/soft tissue (M1c), 18F-DCFPyL-PET/CT detection rates including lesion counts were systematically analyzed. Three central, blinded, and independent readers evaluated the 18F-DCFPyL scans. Results: In this study, 82 (70%) patients had baseline radiographic M1 stage disease (14 patients with M1a, 50 patients with M1b, 18 patients with M1c) and 33 (28%) patients were M0 stage at baseline by central conventional imaging review; two patients were unevaluable. 18F-DCFPyL-PET/CT up-staged 58% (19/33) of pts from M0 to M1, of whom 91% (10/11) who underwent an extra-pelvic biopsy were confirmed to have M1 disease by pathology, including 9 patients with M1b and 1 patient with M1a. Of the patients who were staged M1 at baseline, 18F-DCFPyL-PET/CT upstaged 16% (10/64; M1a to M1b or M1c: n = 4; M1b to M1c: n = 6) of pts to a higher M1 sub-stage and down-staged 22% (18/82) to M0. Conclusions: 18F-DCFPyL-PET/CT identified M1 disease in the majority of patients examined who otherwise had locoregional disease. These data suggest that 18F-DCFPyL-PET/CT may be a useful tool in properly staging men with both metastatic and nonmetastatic relapsed disease, which could lead to superior treatment paradigms than currently exist using conventional imaging. Clinical trial information: NCT02981368.

Immunomodulatory Activity of a Colony-stimulating Factor-1 Receptor Inhibitor in Patients with Advanced Refractory Breast or Prostate Cancer: A Phase I Study

PURPOSE

Tumor-associated macrophages correlate with increased invasiveness, growth, and immunosuppression. Activation of the colony-stimulating factor-1 receptor (CSF-1R) results in proliferation, differentiation, and migration of monocytes/macrophages. This phase I study evaluated the immunologic and clinical activity, and safety profile of CSF-1R inhibition with the mAb LY3022855.

PATIENTS AND METHODS

Patients with advanced refractory metastatic breast cancer (MBC) or metastatic castration-resistant prostate cancer (mCRPC) were treated with LY3022855 intravenously in 6-week cycles in cohorts: (A) 1.25 mg/kg every 2 weeks (Q2W); (B) 1.0 mg/kg on weeks 1, 2, 4, and 5; (C) 100 mg once weekly; (D)100 mg Q2W. mCRPC patients were enrolled in cohorts A and B; patients with MBC were enrolled in all cohorts. Efficacy was assessed by RECIST and Prostate Cancer Clinical Trials Working Group 2 criteria.

RESULTS

Thirty-four patients (22 MBC; 12 mCRPC) received ≥1 dose of LY3022855. At day 8, circulating CSF-1 levels increased and proinflammatory monocytes CD14^DIMCD16^BRIGHT decreased. Best RECIST response was stable disease in five patients with MBC (23%; duration, 82-302 days) and three patients with mCRPC (25%; duration, 50-124 days). Two patients with MBC (cohort A) had durable stable disease >9 months and a third patient with MBC had palpable reduction in a nontarget neck mass. Immune-related gene activation in tumor biopsies posttreatment was observed. Common any grade treatment-related adverse events were fatigue, decreased appetite, nausea, asymptomatic increased lipase, and creatine phosphokinase.

CONCLUSIONS

LY3022855 was well tolerated and showed evidence of immune modulation. Clinically meaningful stable disease >9 months was observed in two patients with MBC.

Anticoagulation reduces iliocaval and iliofemoral stent thrombosis in patients with cancer stented for nonthrombotic venous obstruction

OBJECTIVE

To identify factors associated with venous stent thrombosis in patients with cancer treated for nonthrombotic iliocaval or iliofemoral venous obstruction.

METHODS

We performed a retrospective review of relevant imaging and medical records from 30 consecutive patients with cancer treated at a single center who underwent venous stent placement for nonthrombotic iliocaval or iliofemoral venous obstruction between 2008 and 2018. Follow-up imaging was used to assess stent patency. Variables examined included patient demographics, cancer type, stent characteristics, anticoagulant, and antiplatelet medications and complications of treatment.

RESULTS

Overall primary stent patency was 83% (25/30). The median follow-up period was 44 days (range, 3-365 days). Ten percent of patients occluded owing to in-stent thrombosis and 7% owing to tumor compression of the stent without thrombosis. Therapeutic poststent anticoagulation with enoxaparin, warfarin, or a factor Xa inhibitor was initiated in 87% of the patients. Stent thrombosis occurred in one patient in the anticoagulation group (4%) at 50 days. Stent thrombosis occurred in two patients in the nonanticoagulation group (50%), one at 9 days and the other at 91 days. Anticoagulation was found to be protective against stent thrombosis in this population (hazard ratio, 0.015; P = .011). No statistically significant associations were found among the remaining variables. One patient in the anticoagulation group experienced major bleeding (1/26 [4%]).

CONCLUSIONS

Iliocaval and iliofemoral stent placement for nonthrombotic malignant venous obstruction is safe with favorable primary patency rates. Therapeutic anticoagulation is associated with less stent thrombosis in patients with cancer stented for nonthrombotic iliocaval and iliofemoral venous obstruction.

11C-Choline PET/CT in Recurrent Prostate Cancer: Retrospective Analysis in a Large U.S. Patient Series

Our purpose was to evaluate the performance of ¹¹C-choline PET/CT in detecting biochemically recurrent prostate cancer (PCa) in a large non-European cohort (in the context of emerging evidence for prostate-specific membrane antigen PET in this setting) and to map patterns of PCa recurrence. Methods: We retrospectively analyzed ¹¹C-choline PET/CT scans from 287 patients who were enrolled in an imaging protocol based on rising prostate-specific antigen (PSA) levels (mean, 3.43 ng/mL; median, 0.94 ng/mL; range, 0.15-89.91 ng/mL) and suspected recurrent PCa. A total of 187 patients had undergone primary radical prostatectomy (RP) (79/187 had secondary radiotherapy), 30 had undergone primary radiotherapy, and 70 had a persistent PSA elevation after receiving initial treatment (69 after RP, 1 after radiotherapy). The level of suspicion for recurrence on ¹¹C-choline PET/CT was scored (0, negative; 1, equivocal; 2, positive) by 2 readers. The correlation between ¹¹C-choline PET/CT positivity and initial treatment, Gleason score, National Comprehensive Cancer Network stage, PSA level, PSA doubling time, PSA velocity, and time between initial treatment and PET imaging was evaluated. Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) criteria were used to map ¹¹C-choline recurrence patterns. Results: Considering scores 1 and 2 as positives, consensus between the 2 readers deemed 66% of the ¹¹C-choline PET/CT scans as positive. When sorted by PSA level, 45% of patients with a PSA of less than 0.5 ng/mL, 56% of patients with a PSA of 0.5-0.99 ng/mL, 70% of patients with a PSA of 1.0-1.99 ng/mL, and 90% of patients with a PSA of at least 2.0 ng/mL scored either 1 or 2 on ¹¹C-choline PET/CT scans. When considering scores of 2 only, ¹¹C-choline PET/CT positivity was 54% (28%, 46%, 62%, and 81%, respectively, for patients with PSA < 0.5 ng/mL, 0.5-0.99 ng/mL, 1.0-1.99 ng/mL, and ≥ 2.0 ng/mL). In multivariate analysis, only PSA level was significantly associated with scan positivity. Pattern analysis showed that pelvic lymph nodes were the most common site of recurrence, and 28% of patients had ¹¹C-choline-positive suspected recurrences outside the initial treatment field. Conclusion: ¹¹C-choline PET/CT can detect PCa recurrence even among patients with low PSA levels when interpretation accounts for the clinical context, providing a certain pretest probability. Until prostate-specific membrane antigen agents are fully approved for PCa, choline PET/CT may provide clinical utility.

Imaging of Small Renal Masses before and after Thermal Ablation

Thermal ablation of small renal masses is increasingly accepted as an alternative to partial nephrectomy, particularly in patients with multiple comorbidities. Many professional societies support this alternate treatment with updated guidelines. Before performing thermal ablation, it is important to stratify risk and assess technical feasibility by evaluating tumor imaging features such as size, location, and centrality. Routine postablation imaging with CT or MRI is necessary for assessment of residual or recurrent tumor, evidence of complications, or new renal masses outside the ablation zone. The normal spectrum and evolution of findings at CT and MRI include a halo appearance of the ablation zone, ablation zone contraction, and ablation zone calcifications. Tumor recurrence frequently manifests at CT or MRI as new nodular enhancement at the periphery of an expanding ablation zone, although it is normal for the ablation zone to enlarge within the first few months. Recognizing early tumor recurrence is important, as small renal masses are often easily treated with repeat ablations. Potential complications of thermal ablation include vascular injury, urine leak, ureteral stricture, nerve injury, and bowel perforation. The risk of these complications may be related to tumor size and location.^©RSNA, 2019.

Macrophage-secreted TGF-β1 contributes to fibroblast activation and ureteral stricture after ablation injury

Iatrogenic injury to the healthy ureter during ureteroscope-guided ablation of malignant or nonmalignant disease can result in ureteral stricture. Transforming growth factor (TGF)-β1-mediated scar formation is considered to underlie ureteral stricture, but the cellular sources of this cytokine and the sequelae preceding iatrogenic stricture formation are unknown. Using a swine model of ureteral injury with irreversible electroporation (IRE), we evaluated the cellular sources of TGF-β1 and scar formation at the site of injury and examined in vitro whether the effects of TGF-β1 could be attenuated by pirfenidone. We observed that proliferation and α-smooth muscle actin expression by fibroblasts were restricted to injured tissue and coincided with proliferation of macrophages. Collagen deposition and scarring of the ureter were associated with increased TGF-β1 expression in both fibroblasts and macrophages. Using in vitro experiments, we demonstrated that macrophages stimulated by cells that were killed with IRE, but not LPS, secreted TGF-β1, consistent with a wound healing phenotype. Furthermore, using 3T3 fibroblasts, we demonstrated that stimulation with paracrine TGF-β1 is necessary and sufficient to promote differentiation of fibroblasts and increase collagen secretion. In vitro, we also showed that treatment with pirfenidone, which modulates TGF-β1 activity, limits proliferation and TGF-β1 secretion in macrophages and scar formation-related activity by fibroblasts. In conclusion, we identified wound healing-related macrophages to be an important source of TGF-β1 in the injured ureter, which may be a paracrine source of TGF-β1 driving scar formation by fibroblasts, resulting in stricture formation.

What Physicians and Health Organizations Should Know About Mandated Imaging Appropriate Use Criteria

The Appropriate Use Criteria Program, enacted by the Centers for Medicare & Medicaid Services in response to the Protecting Access to Medicare Act of 2014 (PAMA), aims to reduce inappropriate and unnecessary imaging by mandating use of clinical decision support (CDS) by all providers who order advanced imaging examinations (magnetic resonance imaging; computed tomography; and nuclear medicine studies, including positron emission tomography). Beginning 1 January 2020, documentation of an interaction with a certified CDS system using approved appropriate use criteria will be required on all Medicare claims for advanced imaging in all emergency department patients and outpatients as a prerequisite for payment. The Appropriate Use Criteria Program will initially cover 8 priority clinical areas, including several (such as headache and low back pain) commonly encountered by internal medicine providers. All providers and organizations that order and provide advanced imaging must understand program requirements and their options for compliance strategies. Substantial resources and planning will be needed to comply with PAMA regulations and avoid unintended negative consequences on workflow and payments. However, robust evidence supporting the desired outcome of reducing inappropriate use of advanced imaging is lacking.

Diagnostic performance of 18F-DCFPyL in the OSPREY Trial: A prospective phase 2/3 multicenter study of 18F-DCFPyL PET/CT imaging in patients (Pts) with known or suspected metastatic prostate cancer (mPC)

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Background: Accurate detection of prostate cancer is imperative to patient management, yet standard imaging methods perform poorly in accurately detecting mPC. 18F-DCFPyL is a novel PET imaging agent that selectively binds to prostate-specific membrane antigen, a recognized target for prostate cancer. OSPREY was a prospective, multicenter study in pts with either newly diagnosed high-risk prostate cancer (cohort A), or known or suspected mPC (cohort B). Here we focus on Cohort B. Methods: 117 men planned for biopsy of recurrent or mPC received 18F-DCFPyL. Pts underwent image-guided biopsy. Sensitivity, positive predictive value (PPV), and safety of 18F-DCFPyL PET/CT were the key endpoints for Cohort B. 18F-DCFPyL PET/CT scans were evaluated by three independent, blinded central readers; and results were compared to histopathology as the truth standard. Results: The sensitivity and PPV of 18F-DCFPyL PET/CT as compared to histopathology ranged from 92.9-98.6% (lower bound of 95% CI: 84.0-91.6%) and 81.2-87.8%, respectively. Diagnostic performance by anatomic location showed high sensitivity and high PPV in all sites of disease (Table). Only two (1.7%) cohort B pts experienced ≥1 drug-related AE (dysgeusia and generalized rash), both were mild (Grade 1) in severity. Conclusions: 18F-DCFPyL PET/CT was well tolerated and demonstrated high sensitivity and PPV in accurately detecting nodal, bone, and visceral/soft tissue metastases. A positive 18F-DCFPyL PET/CT scan is highly likely to represent pathologically proven distant disease, demonstrating the potential of 18F-DCFPyL as a PET imaging agent to favorably influence treatment planning. Clinical trial information: NCT02981368. [Table: see text]

A pilot safety study of gemcitabine and cisplatin (GC) with atezolizumab (A) as first-line therapy in patients (pts) with metastatic urothelial cancer (mUC)

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Background: GC has a high overall response rate (ORR) but a high relapse rate in pts with untreated mUC. Inhibition of programmed death-ligand 1 (PD-L1) with A can lead to long-term survival, but single-agent ORR is modest. We report the outcomes of GC+A in a cohort pts with mUC. Methods: This study was designed to assess the safety of GC + A in 10 pts with untreated mUC prior to testing GC + A in a neoadjuvant study in pts with muscle-invasive disease. The primary endpoint was safety as assessed by a predefined dose limiting toxicity (DLT) rate during the first cycle in the first 6 pts. Total accrual goal was 10 pts to collect preliminary data on ORR and progression-free survival (PFS). RECIST 1.1 assessments were performed every 9 wks. Pts received 6 cycles of GC + A induction and then A maintenance every 3 wks. Results: No DLTs occurred during the first cycle in the first 6 pts. Grades 3-4 neutropenia and anemia occurred in 6/10 and 7/10 pts, respectively. Three pts required gemcitabine dose reductions for hematologic toxicity and 2 pts had febrile neutropenia. One pt discontinued cisplatin after 2 cycles for grade 3 hearing impairment but completed induction with gemcitabine and A. Only 1 pt discontinued study therapy due to treatment-related adverse events (AEs), including A-related grade 4 encephalopathy and grade 3 polyneuropathy. Three of 10 pts had visceral (liver or bone) metastases. Of the 10 pts, 1 pt is completing induction but meets initial criteria for partial response (PR), 8 pts had confirmed PR, and 1 pt had progressive disease (PD). Of 9 pts with confirmatory scans, the median PFS was 10.6 months (95% CI 6.7, N/A). Of 8 pts with confirmed PR, 5 eventually had PD, 1 has just completed induction, 1 remains without PD at 25 months, and 1 had consolidation surgery with a pathologic complete response and remains disease-free at 21 months. Conclusions: This 10 pt study met its primary safety endpoint. The neoadjuvant study is ongoing (NCT02989584). Although there were a substantial number of grade 3-4 toxicities, therapy was discontinued due to treatment-related AEs in only 1 pt. Immune correlative studies are ongoing. Clinical trial information: NCT02989584.

Utility of Core Biopsy Specimen to Identify Histologic Subtype and Predict Outcome for Lung Adenocarcinoma

BACKGROUND

Lung adenocarcinoma histologic subtype is an important indicator of patient outcomes, so preoperative knowledge of subtype may be helpful to guide surgical planning. We evaluated the sensitivity and prognostic efficacy of specimens from computed tomography-guided core needle biopsies to predict histologic subtype and patient outcome after surgery.

METHODS

We retrospectively identified 221 patients with lung adenocarcinoma who underwent computed tomography-guided lung biopsy and subsequent surgical resection. Concordance, accuracy, specificity, and sensitivity of histologic subtypes from core biopsy specimens were compared with surgically resected specimens. Tumor characteristics and biopsy procedural factors were analyzed to determine impact on diagnostic sensitivity. Histologic subtype based on biopsy specimen, clinical, tumor, and treatment variables were also examined in relation to time to progression.

RESULTS

Overall concordance of biopsy samples with the predominant subtype from surgical specimens was 77%. Specificity (sensitivity) of detecting a nonaggressive and aggressive subtype were 86% (93%) and 95% (48%), respectively. Length of core specimen and percentage subtype composition in the surgically resected specimen were correlated with improved sensitivity but to a lesser extent with aggressive subtypes. Presence of an aggressive subtype in biopsy specimens was an independent predictor of progression after surgery (subdistribution hazard ratio, 2.51; 95% confidence interval, 1.28-4.94; p = 0.0075).

CONCLUSIONS

Specimens from computed tomography-guided core biopsies can predict lung adenocarcinoma progression after surgical resection. Future prospective studies should address the role of core biopsy in preoperative planning.

Caveolin-1 mediates cellular distribution of HER2 and affects trastuzumab binding and therapeutic efficacy

Human epidermal growth factor receptor 2 (HER2) gene amplification and/or protein overexpression in tumors is a prerequisite for initiation of trastuzumab therapy. Although HER2 is a cell membrane receptor, differential rates of endocytosis and recycling engender a dynamic surface pool of HER2. Since trastuzumab must bind to the extracellular domain of HER2, a depressed HER2 surface pool hinders binding. Using in vivo biological models and cultures of fresh human tumors, we find that the caveolin-1 (CAV1) protein is involved in HER2 cell membrane dynamics within the context of receptor endocytosis. The translational significance of this finding is highlighted by our observation that temporal CAV1 depletion with lovastatin increases HER2 half-life and availability at the cell membrane resulting in improved trastuzumab binding and therapy against HER2-positive tumors. These data show the important role that CAV1 plays in the effectiveness of trastuzumab to target HER2-positive tumors.

Trastuzumab binding to tumor cells depends on the availability of HER2 at the cell membrane. Here the authors show that caveolin-1 (CAV1) regulates HER2 density at the cell membranes and that CAV1 gene knockdown or protein depletion via the cholesterol modulator lovastatin, increases trastuzumab binding and anti-tumor activity.

Autologous Blood Patch Injection versus Hydrogel Plug in CT-guided Lung Biopsy: A Prospective Randomized Trial

Purpose To compare the effect of autologous blood patch injection (ABPI) with that of a hydrogel plug on the rate of pneumothorax at CT-guided percutaneous lung biopsy. Materials and Methods In this prospective randomized controlled trial ( https://ClinicalTrials.gov , NCT02224924), a noninferiority design was used for ABPI, with a 10% noninferiority margin when compared with the hydrogel plug, with the primary outcome of pneumothorax rate within 2 hours of biopsy. A type I error rate of 0.05 and 90% power were specified with a target study population of 552 participants (276 in each arm). From October 2014 to February 2017, all potential study participants referred for CT-guided lung biopsy (n = 2052) were assessed for enrollment. Results The data safety monitoring board recommended the trial be closed to accrual after an interim analysis met prespecified criteria for early stopping based on noninferiority. The final study group consisted of 453 participants who were randomly assigned to the ABPI (n = 226) or hydrogel plug (n = 227) arms. Of these, 407 underwent lung biopsy. Pneumothorax rates within 2 hours of biopsy were 21% (42 of 199) and 29% (60 of 208); chest tube rates were 9% (18 of 199) and 13% (27 of 208); and delayed pneumothorax rates within 2 weeks after biopsy were 1.4% (three of 199) and 1.5% (three of 208) in the ABPI and hydrogel plug arms, respectively. Conclusion Autologous blood patch injection is noninferior to a hydrogel plug regarding the rate of pneumothorax after CT-guided percutaneous lung biopsy. © RSNA, 2018 Online supplemental material is available for this article.

Volumetric 3D assessment of ablation zones after thermal ablation of colorectal liver metastases to improve prediction of local tumor progression

PURPOSE

The goal of this study was to develop and evaluate a volumetric three-dimensional (3D) approach to improve the accuracy of ablation margin assessment following thermal ablation of hepatic tumors.

METHODS

The 3D margin assessment technique was developed to generate the new 3D assessment metrics: volumes of insufficient coverage (VICs) measuring volume of tissue at risk post-ablation. VICs were computed for the tumor and tumor plus theoretical 5- and 10-mm margins. The diagnostic accuracy of the 3D assessment to predict 2-year local tumor progression (LTP) was compared to that of manual 2D assessment using retrospective analysis of a patient cohort that has previously been reported as a part of an outcome-centered study. Eighty-six consecutive patients with 108 colorectal cancer liver metastases treated with radiofrequency ablation (2002-2012) were used for evaluation. The 2-year LTP discrimination power was assessed using receiver operating characteristic area under the curve (AUC) analysis.

RESULTS

A 3D assessment of margins was successfully completed for 93 out of 108 tumors. The minimum margin size measured using the 3D method had higher discrimination power compared with the 2D method, with an AUC value of 0.893 vs. 0.790 (p = 0.01). The new 5-mm VIC metric had the highest 2-year LTP discrimination power with an AUC value of 0.923 (p = 0.004).

CONCLUSIONS

Volumetric semi-automated 3D assessment of the ablation zone in the liver is feasible and can improve accuracy of 2-year LTP prediction following thermal ablation of hepatic tumors.

KEY POINTS

• More accurate prediction of local tumor progression risk using volumetric 3D ablation zone assessment can help improve the efficacy of image-guided percutaneous thermal ablation of hepatic tumors. • The accuracy of evaluation of ablation zone margins after thermal ablation of colorectal liver metastases can be improved using a volumetric 3D semi-automated assessment approach and the volume of insufficient coverage assessment metric. • The new 5-mm volume-of-insufficient-coverage metric, indicating the volume of tumor plus 5-mm margin that remained untreated, had the highest 2-year local tumor progression discrimination power.

Percutaneous Ablation Versus Partial and Radical Nephrectomy for T1a Renal Cancer: A Population-Based Analysis

Background

Stage T1a renal cell carcinoma (RCC) (tumors <4 cm) is usually curable. Nephron-sparing partial nephrectomy (PN) has replaced radical nephrectomy (RN) as the standard of care for these tumors. Radical nephrectomy remains the first alternative treatment option, whereas percutaneous ablation (PA), a newer, nonsurgical treatment, is recommended less strongly because of the relative paucity of comparative PA data.

Objective

To compare PA, PN, and RN outcomes.

Design

Observational cohort analysis using inverse probability of treatment-weighted propensity scores.

Setting

Population-based SEER (Surveillance, Epidemiology, and End Results) cancer registry data linked to Medicare claims.

Patients

Persons aged 66 years or older who received treatment for T1a RCC between 2006 and 2011.

Interventions

PA versus PN and RN.

Measurements

RCC-specific and overall survival, 30- and 365-day postintervention complications.

Results

4310 patients were followed for a median of 52 months for overall survival and 42 months for RCC-specific survival. After PA versus PN, the 5-year RCC-specific survival rate was 95% (95% CI, 93% to 98%) versus 98% (CI, 96% to 99%); after PA versus RN, 96% (CI, 94% to 98%) versus 95% (CI, 93% to 96%). After PA versus PN, the 5-year overall survival rate was 77% (CI, 74% to 81%) versus 86% (CI, 84% to 88%); after PA versus RN, 74% (CI, 71% to 78%) versus 75% (CI, 73% to 77%). Cumulative rates of renal insufficiency 31 to 365 days after PA, PN, and RN were 11% (CI, 8% to 14%), 9% (CI, 8% to 10%), and 18% (CI, 17% to 20%), respectively. Rates of nonurologic complications within 30 days after PA, PN, and RN were 6% (CI, 4% to 9%), 29% (CI, 27% to 30%), and 30% (CI, 28% to 32%), respectively. Ten percent of patients in the PN group had intraoperative conversion to RN. Seven percent of patients in the PA group received additional PA within 1 year of treatment.

Limitations

Analysis of observational data may have been affected by residual confounding by provider or from selection bias toward younger, healthier patients in the PN group. Findings from this older study population are probably less applicable to younger patients. Use of SEER-Medicare linked files prevented analysis of patients who received treatment after 2011, possibly reducing generalizability to the newest PA, PN, and RN techniques.

Conclusion

For well-selected older adults with T1a RCC, PA may result in oncologic outcomes similar to those of RN, but with less long-term renal insufficiency and markedly fewer periprocedural complications. Compared with PN, PA may be associated with slightly shorter RCC-specific survival but fewer periprocedural complications.

Primary Funding Source

Association of University Radiologists GE Radiology Research Academic Fellowship and Society of Interventional Radiology Foundation.

Pirfenidone inhibits cryoablation induced local macrophage infiltration along with its associated TGFb1 expression and serum cytokine level in a mouse model

PURPOSE

To investigate the effects of pirfenidone (PFD) on post-cryoablation inflammation in a mouse model.

MATERIALS AND METHODS

In this IACUC-approved study, eighty Balb/c mice were randomly divided into four groups (20/group): sham + vehicle, sham + PFD, cryoablation + vehicle, and cryoablation + PFD. For cryoablation groups, a 20% freeze rate cryoablation (20 s to less than -100 °C) was used to ablate normal muscle in the right flank. For sham groups, the cryoprobe was advanced into the flank and maintained for 20 s without ablation. PFD or vehicle solution was intraperitoneally injected (5 mg/kg) at days 0, 1, 2, 3, and then every other day until day 13 after cryoablation. Mice were euthanized at days 1, 3, 7, and 14. Blood samples were used for serum IL-6, IL-10, and TGFβ1 analysis using electrochemiluminescence and ELISA assays, respectively. Immunohistochemistry-stained ablated tissues were used to analyze macrophage infiltration and local TGFβ1 expression in the border region surrounding the cryoablation-induced coagulation zone.

RESULTS

Cryoablation induced macrophage infiltration and increased TGFβ1 expression in the border of the necrotic zone, and high levels of serum IL-6, peaking at days 7 (70.5 ± 8.46/HPF), 14 (228 ± 18.36/HPF), and 7 (298.67 ± 92.63), respectively. Animals receiving PFD showed reduced macrophage infiltration (35.5 ± 16.93/HPF at day 7, p < 0.01) and cytokine levels (60.2 ± 7.6/HPF at day 14, p < 0.01). PFD also significantly reduced serum IL-6 levels (p < 0.001 vs. all non-PFD groups).

CONCLUSIONS

PFD mitigates cryoablation induced muscle tissue macrophage infiltration, increased IL-6 levels, and local TGFβ1 expression in a small animal model.

Sixteen-year percutaneous renal mass ablation trends: Results from the Ablation of Renal Masses Outcomes Registry (ARMOR)

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Background: Existing data suggest that percutaneous renal mass ablation offers favorable rates of disease control with lower cost and fewer complications relative to surgical interventions. Despite increasing utilization, little is known about changes in practice patterns and patient selection over time as new technologies have emerged and indications for renal ablation have been refined. Methods: Institutional review board approval was granted with a waiver of informed consent to review data from the multinational Ablation of Renal Masses Outcomes Registry (ARMOR), which is composed of adult ablation patients with biopsied renal masses. Patient demographics, ablation modality, timing of renal biopsy, malignancy rate, method of anesthesia, and type of imaging guidance from 2001-2016 were reviewed. Analyses were conducted using generalized mixed modeling assuming normal or binary distribution with sandwich estimation, where observations were nested within participating institutions. Variables were modeled over time using SAS/GLIMMIX with significance set at α = 0.05. Results: Data from 768 patients at eleven institutions were available for review. Average patient age was 67.7±11.7 years (male:female, 1.9:1), which remained unchanged throughout the study period. Radiofrequency ablation (RFA) was the most commonly utilized modality from 2001-2007 but decreased thereafter, with cryoablation favored from 2008-2012. By 2016, RFA, microwave (MWA), and cryoablation were all used with relative equipoise, though a significant trend toward increased MWA utilization was found beginning in 2010 (OR: 1.28; p = 0.004). A significant increase in the frequency of same-day biopsy was observed relative to pre-ablation biopsy (OR: 1.16; p = 0.003) alongside a trend toward increasing rates of benign histology (p = 0.08). Use of CT guidance and general anesthesia increased by 4% and 5%, respectively. Conclusions: ARMOR data illustrate fluctuating practice patterns, with increasing use of microwave ablation technology. Growing utilization of concurrent renal mass biopsy and ablation may be contributing to the observed trend toward increased rates of ablation for benign tumors.

Immediate Postablation 18F-FDG Injection and Corresponding SUV Are Surrogate Biomarkers of Local Tumor Progression After Thermal Ablation of Colorectal Carcinoma Liver Metastases

The aim of this study was to determine whether intraprocedural ¹⁸F-FDG PET/CT can be used as a predictor of local tumor progression after percutaneous ablation of colorectal liver metastases. Methods: In this institutional review board-approved prospective study, 39 patients (19 men and 20 women; median age, 56 y) underwent split-dose ¹⁸F-FDG PET/CT-guided ablation followed by immediate biopsy and contrast-enhanced CT imaging of the ablation zone. Binary categorization of biopsy tissues was performed on the basis of the presence of only nonviable coagulation necrosis or viable tumor cells. Minimum ablation margin measurements from contrast-enhanced CT imaging were categorized as 0 mm, 1-4 mm, 5-9 mm, or greater than or equal to 10 mm. SUVs were obtained from PET/CT imaging, and SUV ratios were calculated from 3-dimensional regions of interest located in the ablation zone and surrounding normal liver. All predictive variables (biopsy, minimum margin distance, and SUV ratio) were evaluated as predictors of time to local tumor progression identified on imaging using competing-risks regression models (uni- and multivariate analyses). Results: A total of 62 consecutive ablations were evaluated. The mean SUV ratio was significantly higher for viable tumor-positive immediate postablation biopsies (n = 10) than for tumor-negative biopsies (n = 52) (85.8 ± 92.2 vs. 42.3 ± 45.5) (P = 0.03) and for a minimum margin size of less than 5 mm (n = 15) than for a minimum margin size of greater than or equal to 5 mm (n = 47) (78.5 ± 99.1 vs. 38.3 ± 78.5) (P = 0.01). After a median follow-up period of 22.5 (range, 7-52) months, 23 of 62 ablated tumors showed local tumor progression (37.1%). The local tumor progression rate was significantly higher for viable tumor-positive biopsies (8/10) than for negative biopsies (15/52) (80% vs. 29%) (P = 0.001) and for a minimum margin size of less than 5 mm (9/15) than for a minimum margin size of greater than or equal to 10 mm (2/15) (60% vs. 13%) (P = 0.02) but not 5-9 mm (37.5%; 12/32) (P = 0.5). In a competing-risks analysis, biopsy results (P = 0.07) and the minimum margin size (P = 0.08) were borderline significant, but the SUV ratio was not (P = 0.22). However, for negative biopsy ablations, the minimum margin size and SUV ratio were predictive imaging factors for local tumor progression; subdistribution hazard ratios were 0.564 (0.325-0.978) (P = 0.04) and 1.005 (1.001-1.009) (P = 0.005), respectively. Conclusion: The SUV ratio and minimum margin size can independently predict colorectal metastasis local tumor progression after liver ablation when there are no viable tumor cells on immediate postablation biopsies.

Transmural ablation of the normal porcine common bile duct with catheter-directed irreversible electroporation is feasible and does not affect duct patency

BACKGROUND AND AIMS

The aim of this study was to evaluate the feasibility and early safety of catheter-directed irreversible electroporation (IRE) of the normal common bile duct (CBD) in swine.

METHODS

IRE (2000 V, 90 pulses, 100 μs pulse) was performed in the CBD of 6 Yorkshire pigs using a catheter electrode under endoscopic guidance. Ductal patency was assessed with immediate retrograde cholangiography and contrast-enhanced CT imaging at 1 or 7 days after treatment. Animals were killed at either 1 day (n = 4, 2 ablations/animal) or 7 days (n = 2, 1 ablation/animal) after treatment. The biliary tract was extracted en bloc and the length of the ablation along the CBD mucosa was measured. The depth of ablation was quantified using cross-sections of the treated CBD wall stained with hematoxylin and eosin. Single-sample hypothesis testing was performed to verify whether the depth of ablation in the CBD was a representative outcome of IRE treatment.

RESULTS

IRE of the CBD did not result in perforation or obstruction of the organ at 1 or 7 days after treatment. The length of ablation along the CBD mucosa was 17.27 ± 5.55 mm on day 1 samples, and transmural ablation of the CBD wall was a representative outcome of the treatment (7/8 samples, P < .05). Day 1 samples demonstrated loss of epithelium, transmural necrosis, with preservation of lumen integrity. Day 7 samples demonstrated re-epithelialization, with diffuse transmural fibrosis of the CBD wall. These findings were absent from sham tissue samples.

CONCLUSIONS

Intraluminal catheter-directed IRE is feasible and safe for full-thickness ablation of the normal porcine CBD without affecting lumen patency up to 1 week after treatment.

Tumor Xenografts of Human Clear Cell Renal Cell Carcinoma But Not Corresponding Cell Lines Recapitulate Clinical Response to Sunitinib: Feasibility of Using Biopsy Samples

BACKGROUND

Parallel development of preclinical models that recapitulate treatment response observed in patients is central to the advancement of personalized medicine.

OBJECTIVE

To evaluate the use of biopsy specimens to develop patient-derived xenografts and the use of corresponding cell lines from renal cell carcinoma (RCC) tumors for the assessment of histopathology, genomics, and treatment response.

DESIGN, SETTING, AND PARTICIPANTS

A total of 74 tumor specimens from 66 patients with RCC were implanted into immunocompromised NOD-SCID IL2Rg-/- mice. Four cell lines generated from patients' specimens with clear cell pathology were used for comparative studies.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Preclinical models were established and assessed. Engraftment rates were analyzed using chi-square testing. Analysis of variance (two-way analysis of variance) was conducted to assess tumor growth.

RESULTS AND LIMITATIONS

Overall, 33 RCC mouse xenograft models were generated with an overall engraftment rate of 45% (33 of 74). Tumor biopsies engrafted comparably with surgically resected tumors (58% vs 41%; p=0.3). Xenograft tumors and their original tumors showed high fidelity in regard to histology, mutation status, copy number change, and targeted therapy response. Engraftment rates from metastatic tumors were higher but not more significant than primary tumors (54% vs 34%; p=0.091). Our engraftment rate using metastases or biopsies was comparable with recent reports using resected primary tumors. In stark contrast to corresponding cell lines, all tested xenografts recapitulated patients' clinical response to sunitinib.

CONCLUSIONS

Patient-derived xenograft models can be effectively established from tumor biopsies. Preclinical xenograft models but not matched cell lines reflected clinical responses to sunitinib.

PATIENT SUMMARY

Matched patient-derived clear cell renal cell carcinoma xenografts and cell lines from responsive and refractory patients treated with sunitinib were established and evaluated for pharmacologic response to anti-vascular endothelial growth factor treatment. Both models accurately reflected the genetic characteristics of original tumors, but only xenografts recapitulated drug responses observed in patients. These models could serve as a powerful platform for precision medicine.

Contrast enhanced ultrasound imaging can predict vascular-targeted photodynamic therapy induced tumor necrosis in small animals

AIMS

To evaluate the accuracy of contrast-enhanced ultrasound (CEUS) for monitoring tumor necrosis following WST-11 vascular targeted photodynamic therapy (VTP) using imaging-pathology correlation.

METHODS

Renal adenocarcinoma cells were injected into the hindlimb of 13 BalB/c mice resulting in tumors ranging from 9.8 to 194.3mm³. US guidance was used to place a laser fiber into the tumor, and VTP was performed. CEUS was performed prior to animal sacrifice, 24h post-VTP. Whole tumors were extracted for histopathologic analysis using H&E and TUNEL staining. Pathology samples corresponding to the CEUS imaging plane were prepared in order to compare the size and extents of tumor necrosis.

RESULTS

Tumor necrosis following VTP appeared as a central region of non-enhancement on CEUS, while viable tumor appeared as patchy regions of enhancement in the tumor periphery. The region of tumor necrosis measured in mean 66% and 64.8% of total tumor area on CEUS and pathology respectively (p=0.2). The size and location of the necrosis on CEUS images and pathology samples were found correlative with no inter-observer difference (weighted kappa of 0.771 and 0.823, respectively).

CONCLUSION

CEUS allows accurate monitoring of VTP induced tumor necrosis in a small animal model.

Long-Half-Life 89Zr-Labeled Radiotracers Can Guide Percutaneous Biopsy Within the PET/CT Suite Without Reinjection of Radiotracer

The rationale for this study was to evaluate the feasibility of within-suite ⁸⁹Zr-labeled radiotracer PET/CT-guided biopsy performed without reinjection. Methods: From 2013 to 2016, 12 patients (7 men, 5 women; mean age, 61 y; range, 40-75 y) with metastatic prostate or breast carcinoma suspected either on imaging or because of biochemical progression underwent 14 percutaneous biopsies after diagnostic PET/CT using ⁸⁹Zr-labeled radiotracers (mean dose, 180 MBq; range, 126-189 MBq) targeting prostate-specific membrane antigen (n = 7) or human epidermal growth factor receptor 2 (n = 5). Biopsy was performed within a PET/CT suite without radiotracer reinjection. Results: There were no complications in any biopsies, which were performed a mean of 6.2 d (range, 0-13 d) after injection of the radiotracer. The biopsy sites were bone (n = 7), pleura (n = 3), lymph nodes (n = 2), and liver (n = 2). On pathologic examination of the biopsy samples, all were positive for malignancy. The initial diagnostic imaging findings were concordant with the biopsy results. The additional radiation (mean dose-length product) due to the CT procedures was 1,581 mGy/cm (range, 379-2,686 mGy/cm). Conclusion: PET/CT-guided biopsy using ⁸⁹Zr-labeled radiotracers is safe and effective without tracer reinjection.

The Importance of Biopsy in the Era of Molecular Medicine

Recent advances in the molecular characterization of cancers have triggered interest in developing a new taxonomy of disease in oncology with the goal of using the molecular profile of a patient's tumor to predict response to treatment. Image-guided needle biopsy is central to this "precision medicine" effort. In this review, we first discuss the current role of biopsy in relation to clinical examples of molecular medicine. We then outline important bottlenecks to the advancement of precision medicine and highlight the potential role of image-guided biopsy to address these challenges.

Prospective Genomic Profiling of Prostate Cancer Across Disease States Reveals Germline and Somatic Alterations That May Affect Clinical Decision Making

PURPOSE

A long natural history and a predominant osseous pattern of metastatic spread are impediments to the adoption of precision medicine in patients with prostate cancer. To establish the feasibility of clinical genomic profiling in the disease, we performed targeted deep sequencing of tumor and normal DNA from patients with locoregional, metastatic non-castrate, and metastatic castration-resistant prostate cancer (CRPC).

METHODS

Patients consented to genomic analysis of their tumor and germline DNA. A hybridization capture-based clinical assay was employed to identify single nucleotide variations, small insertions and deletions, copy number alterations and structural rearrangements in over 300 cancer-related genes in tumors and matched normal blood.

RESULTS

We successfully sequenced 504 tumors from 451 patients with prostate cancer. Potentially actionable alterations were identified in DNA damage repair (DDR), PI3K, and MAP kinase pathways. 27% of patients harbored a germline or a somatic alteration in a DDR gene that may predict for response to PARP inhibition. Profiling of matched tumors from individual patients revealed that somatic TP53 and BRCA2 alterations arose early in tumors from patients who eventually developed metastatic disease. In contrast, comparative analysis across disease states revealed that APC alterations were enriched in metastatic tumors, while ATM alterations were specifically enriched in CRPC.

CONCLUSION

Through genomic profiling of prostate tumors representing the disease clinical spectrum, we identified a high frequency of potentially actionable alterations and possible drivers of disease initiation, metastasis and castration-resistance. Our findings support the routine use of tumor and germline DNA profiling for patients with advanced prostate cancer, for the purpose of guiding enrollment in targeted clinical trials and counseling families at increased risk of malignancy.

A Comparative Study of Ablation Boundary Sharpness After Percutaneous Radiofrequency, Cryo-, Microwave, and Irreversible Electroporation Ablation in Normal Swine Liver and Kidneys

PURPOSE

To compare ablation boundary sharpness after percutaneous radiofrequency ablation (RFA), cryoablation (CA), microwave ablation (MWA) and irreversible electroporation (IRE) ablation in normal swine liver and kidney.

MATERIALS AND METHODS

Percutaneous CT-guided RFA (n = 5), CA (n = 5), MWA (n = 5) and IRE (n = 5) were performed in the liver and kidney of four Yorkshire pigs. Parameters were chosen to produce ablations 2-3 cm in diameter with a single ablation probe. Contrast-enhanced CT imaging was performed 24 h after ablation, and animals were killed. Treated organs were removed and processed for histologic analysis with hematoxylin and eosin, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). Three readers independently analyzed CT, H&E and TUNEL stained images of the ablation boundary to delineate regions of (1) viable cells, (2) complete necrosis or (3) mixture of viable and necrotic cells which was defined as the transition zone (TZ). The width of TZ was compared across the techniques and organs.

RESULTS

Ablations appeared as non-contrast-enhancing regions on CT with sharp transition to enhancing normal tissue. On TUNEL stained slides, the mean width (μm) of the TZ after MWA was 319 ± 157 in liver and 267 ± 95 in kidney, which was significantly lower than RFA (811 ± 477 and 938 ± 429); CA (452 ± 222 and 700 ± 563); and IRE (1319 ± 682 and 1570 ± 962) (all p < 0.01). No significant differences were observed between the organs.

CONCLUSION

Under similar conditions, the width of the TZ at the ablation boundary varies significantly between different ablation techniques.

Development of a Searchable Database of Cryoablation Simulations for Use in Treatment Planning

PURPOSE

To create and validate a planning tool for multiple-probe cryoablation, using simulations of ice ball size and shape for various ablation probe configurations, ablation times, and types of tissue ablated.

MATERIALS AND METHODS

Ice ball size and shape was simulated using the Pennes bioheat equation. Five thousand six hundred and seventy different cryoablation procedures were simulated, using 1-6 cryoablation probes and 1-2 cm spacing between probes. The resulting ice ball was measured along three perpendicular axes and recorded in a database. Simulated ice ball sizes were compared to gel experiments (26 measurements) and clinical cryoablation cases (42 measurements). The clinical cryoablation measurements were obtained from a HIPAA-compliant retrospective review of kidney and liver cryoablation procedures between January 2015 and February 2016. Finally, we created a web-based cryoablation planning tool, which uses the cryoablation simulation database to look up the probe spacing and ablation time that produces the desired ice ball shape and dimensions.

RESULTS

Average absolute error between the simulated and experimentally measured ice balls was 1 mm in gel experiments and 4 mm in clinical cryoablation cases. The simulations accurately predicted the degree of synergy in multiple-probe ablations. The cryoablation simulation database covers a wide range of ice ball sizes and shapes up to 9.8 cm.

CONCLUSION

Cryoablation simulations accurately predict the ice ball size in multiple-probe ablations. The cryoablation database can be used to plan ablation procedures: given the desired ice ball size and shape, it will find the number and type of probes, probe configuration and spacing, and ablation time required.

Standardized Reporting in IR: A Prospective Multi-Institutional Pilot Study

PURPOSE

To assess adoption and survey-based satisfaction rates following deployment of standardized interventional radiology (IR) procedure reports across multiple institutions.

MATERIALS AND METHODS

Standardized reporting templates for 5 common interventional procedures (central venous access, inferior vena cava [IVC] filter insertion, IVC filter removal, uterine artery embolization, and vertebral augmentation) were distributed to 20 IR practices in a prospective quality-improvement study. Participating sites edited the reports according to institutional preferences and deployed them for a 1-year pilot study concluding in July 2015. Study compliance was measured by sampling 20 reports of each procedure type at each institution, and surveys of interventionalists and referring physicians were performed. Modifications to the standardized reporting templates at each site were analyzed.

RESULTS

Ten institutions deployed the standardized reports, with 8 achieving deployment of 3-12 months. The mean report usage rate was 57%. Each site modified the original reports, with 26% mean reduction in length, 18% mean reduction in wordiness, and 60% mean reduction in the number of forced fill-in fields requiring user input. Linear-regression analysis revealed that reduced number of forced fill-in fields correlated significantly with increased usage rate (R² = 0.444; P = .05). Surveys revealed high satisfaction rates among referring physicians but lower satisfaction rates among interventional radiologists.

CONCLUSIONS

Standardized report adoption rates increased when reports were simplified by reducing the number of forced fill-in fields. Referring physicians preferred the standardized reports, whereas interventional radiologists preferred standard narrative reports.

Managing Complications Following Nephron-Sparing Procedures for Renal Masses

Small renal malignancies are commonly treated with nephron-sparing procedures including partial nephrectomy and percutaneous ablation. Although these procedures offer faster patient recovery and preserve renal function, a variety of complications can occur. Here, we review vascular and nonvascular complications associated with nephron-sparing renal mass treatments and discuss options for minimally invasive image-guided management.

Deep Sequencing of T-cell Receptor DNA as a Biomarker of Clonally Expanded TILs in Breast Cancer after Immunotherapy

In early-stage breast cancer, the degree of tumor-infiltrating lymphocytes (TIL) predicts response to chemotherapy and overall survival. Combination immunotherapy with immune checkpoint antibody plus tumor cryoablation can induce lymphocytic infiltrates and improve survival in mice. We used T-cell receptor (TCR) DNA sequencing to evaluate both the effect of cryoimmunotherapy in humans and the feasibility of TCR sequencing in early-stage breast cancer. In a pilot clinical trial, 18 women with early-stage breast cancer were treated preoperatively with cryoablation, single-dose anti-CTLA-4 (ipilimumab), or cryoablation + ipilimumab. TCRs within serially collected peripheral blood and tumor tissue were sequenced. In baseline tumor tissues, T-cell density as measured by TCR sequencing correlated with TIL scores obtained by hematoxylin and eosin (H&E) staining. However, tumors with little or no lymphocytes by H&E contained up to 3.6 × 10⁶ TCR DNA sequences, highlighting the sensitivity of the ImmunoSEQ platform. In this dataset, ipilimumab increased intratumoral T-cell density over time, whereas cryoablation ± ipilimumab diversified and remodeled the intratumoral T-cell clonal repertoire. Compared with monotherapy, cryoablation plus ipilimumab was associated with numerically greater numbers of peripheral blood and intratumoral T-cell clones expanding robustly following therapy. In conclusion, TCR sequencing correlates with H&E lymphocyte scoring and provides additional information on clonal diversity. These findings support further study of the use of TCR sequencing as a biomarker for T-cell responses to therapy and for the study of cryoimmunotherapy in early-stage breast cancer. Cancer Immunol Res; 4(10); 835-44. ©2016 AACR.

A Pilot Study of Preoperative Single-Dose Ipilimumab and/or Cryoablation in Women with Early-Stage Breast Cancer with Comprehensive Immune Profiling

PURPOSE

To assess the safety and tolerability of preoperative cryoablation-mediated tumor antigen presentation and/or ipilimumab-mediated immune modulation in women with operable breast cancer.

EXPERIMENTAL DESIGN

In this pilot study, 19 women with breast cancer for whom mastectomy was planned were treated with preoperative tumor cryoablation (n = 7), single-dose ipilimumab at 10 mg/kg (n = 6), or both (n = 6). The primary outcome for this pilot study was safety/tolerability as defined as freedom from delays in pre-planned, curative-intent mastectomy. Exploratory studies of immune activation were performed on peripheral blood and tumor.

RESULTS

Preoperative cryoablation and/or ipilimumab were safe and tolerable, with no delays in pre-planned surgery. Grade III toxicity was seen in 1 of 19 (unrelated rash after ipilimumab). Combination therapy was associated with sustained peripheral elevations in: Th1-type cytokines, activated (ICOS⁺) and proliferating (Ki67⁺) CD4⁺ and CD8⁺ T cells, and posttreatment proliferative T-effector cells relative to T-regulatory cells within tumor.

CONCLUSIONS

Preoperative cryoablation and single-dose ipilimumab are safe alone or in combination with no surgical delays incurred. Potentially favorable intratumoral and systemic immunologic effects were observed with the combination, suggesting the possibility for induced and synergistic antitumor immunity with this strategy. Clin Cancer Res; 22(23); 5729-37. ©2016 AACR.

Pilot Study to Assess Safety and Clinical Outcomes of Irreversible Electroporation for Partial Gland Ablation in Men with Prostate Cancer

PURPOSE

Partial prostate gland ablation is a strategy to manage localized prostate cancer. Irreversible electroporation can ablate localized soft tissues. We describe 30 and 90-day complications and intermediate term functional outcomes in men undergoing prostate gland ablation using irreversible electroporation.

MATERIALS AND METHODS

We reviewed the charts of 25 patients with prostate cancer who underwent prostate gland ablation using irreversible electroporation as a primary procedure and who were followed for at least 6 months.

RESULTS

Median followup was 10.9 months. Grade 3 complications occurred in 2 patients including epididymitis (1) and urinary tract infection (1). Fourteen patients experienced grade 2 or lower complications, mainly transient urinary symptoms, hematuria and urinary tract infections. Of 25 patients 4 (16%) had cancer in the zone of ablation on routine followup biopsy at 6 months. Of those with normal urinary function at baseline 88% and 94% reported normal urinary function at 6 and 12 months after prostate gland ablation, respectively. By 12 months only 1 patient with normal erectile function at baseline reported new difficulty with potency and only 2 patients (8%) required a pad for urinary incontinence.

CONCLUSIONS

Prostate gland ablation with irreversible electroporation is feasible and safe in selected men with localized prostate cancer. Intermediate term urinary and erectile function outcomes appear reasonable. Irreversible electroporation is effective in the ablation of tumor bearing prostate tissue as a majority of men had no evidence of residual cancer on biopsy 6 months after prostate gland ablation.

Nonthermal Ablation by Using Intravascular Oxygen Radical Generation with WST11: Dynamic Tissue Effects and Implications for Focal Therapy

Purpose To examine the hypothesis that vascular-targeted photodynamic therapy (VTP) with WST11 and clinically relevant parameters can be used to ablate target tissues in a non-tumor-bearing large-animal model while selectively sparing blood vessels and collagen. Materials and Methods By using an institutional animal care and use committee-approved protocol, 68 ablations were performed in the kidneys (cortex and medulla) and livers of 27 adult pigs. Posttreatment evaluation was conducted with contrast material-enhanced computed tomography in the live animals at 24 hours. Immunohistochemistry was evaluated and histologic examination with hematoxylin-eosin staining was performed at 4 hours, 24 hours, and 7 days. Intravenous infusion of WST11 (4 mg per kilogram of body weight) was followed by using near-infrared illumination (753 nm for 20 minutes) through optical fibers prepositioned in target tissues by using a fixed template. Treated areas were scanned, measured, and statistically analyzed by using the Student t test and two-way analysis of variance. Results Focal WST11 VTP treatment in the liver and kidney by using a single optical fiber resulted in well-demarcated cylindrical zones of nonthermal necrosis concentrically oriented around the light-emitting diffuser, with no intervening viable parenchymal cells. The radius of ablated tissue increased from approximately 5 mm at 150 mW to approximately 7 mm at 415 mW (P < .01). Illumination through fiber triads at 1-cm separation resulted in confluent homogeneous necrosis. Patterns of acute injury within 24 hours were consistent with microcirculatory flow arrest and collagen preservation (demonstrated with trichrome staining). In the peripheral ablation zone, blood vessels at least 40 μm in diameter were selectively preserved and remained functional at 7 days. Ablated tissues exhibited progressive fibrosis and chronic inflammatory cell infiltrates. No histologic changes consistent with thermal injury were observed in blood vessels or collagen. The renal hilum and collecting system did not show treatment effect, despite treatment proximity. Conclusion WST11 VTP induces nonthermal tissue ablation in target tissue while preserving critical organ structures and bystander blood vessels within solid organs. (©) RSNA, 2016 Online supplemental material is available for this article.

Comparison of ablation defect on MR imaging with computer simulation estimated treatment zone following irreversible electroporation of patient prostate

To determine whether patient specific numerical simulations of irreversible electroporation (IRE) of the prostate correlates with the treatment effect seen on follow-up MR imaging. Computer models were created using intra-operative US images, post-treatment follow-up MR images and clinical data from six patients receiving IRE. Isoelectric contours drawn using simulation results were compared with MR imaging to estimate the energy threshold separating treated and untreated tissue. Simulation estimates of injury to the neurovascular bundle and rectum were compared with clinical follow-up and patient reported outcomes. At the electric field strength of 700 V/cm, simulation estimated electric field distribution was not different from the ablation defect seen on follow-up MR imaging (p = 0.43). Simulation predicted cross sectional area of treatment (mean 532.33 ± 142.32 mm(2)) corresponded well with the treatment zone seen on MR imaging (mean 540.16 ± 237.13 mm(2)). Simulation results did not suggest injury to the rectum or neurovascular bundle, matching clinical follow-up at 3 months. Computer simulation estimated zone of irreversible electroporation in the prostate at 700 V/cm was comparable to measurements made on follow-up MR imaging. Numerical simulation may aid treatment planning for irreversible electroporation of the prostate in patients.