Risk of adverse pathology at prostatectomy in the era of MRI and targeted biopsies; rethinking active surveillance for intermediate risk prostate cancer patients.

PURPOSE: Men with intermediate risk (IR) prostate cancer (CaP) are often excluded from active surveillance (AS) due to higher rates of adverse pathology (AP). We determined our rate of AP in men who underwent multiparametric MRI (MpMRI) with combined biopsy (CB) consisting of targeted biopsy (TB) and systematic biopsy (SB) prior to radical prostatectomy (RP). METHODS: A retrospective review was conducted of men with Gleason Grade Group (GG) 2 disease who underwent RP after SB alone or after preoperative MRI with CB. AP was defined as either pathologic stage T3a (AP ≥ T3a) or pathologic stage T3b (AP ≥ T3b) and/or GG upgrading. Rates of AP were determined for both groups and those who fit the National Comprehensive Cancer Network (NCCN) definition of favorable IR (FIR) or the low volume IR (LVIR) criteria. Multivariable logistic regression was used to determine predictive factors. RESULTS: The overall rate of AP ≥ T3b was 21.2% in the SB group vs. 8.6% in the MRI with CB group, P = 0.006. This rate was lowered to 6.8% and 5.6% when men met the definition of NCCN FIR or LVIR, respectively. Suspicion for extraprostatic extension (EPE) (OR 7.65, 95% CI 1.77-33.09, P = 0.006) and positive cores of GG 2 on SB (OR 1.43, 95% CI 1.05-1.96, P = 0.023) were significant for predicting AP ≥ T3b. CONCLUSIONS: Rates of AP at RP after MRI with CB are lower than studies prior to the adoption of this technology, suggesting that more men with IR disease may be considered for AS. However, increasing cores positive on SB and MRI findings suggestive of EPE remain unsafe.

Evaluating Biochemically Recurrent Prostate Cancer: Histologic Validation of 18F-DCFPyL PET/CT with Comparison to Multiparametric MRI.

Background Prostate cancer recurrence is found in up to 40% of men with prior definitive (total prostatectomy or whole-prostate radiation) treatment. Prostate-specific membrane antigen PET agents such as 2-(3-{1-carboxy-5-[(6-[18F]fluoro-pyridine 3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (18F-DCFPyL) may improve detection of recurrence compared with multiparametric MRI; however, histopathologic validation is lacking. Purpose To determine the sensitivity, specificity, and positive predictive value (PPV) of 18F-DCFPyL PET/CT based on histologic analysis and to compare with pelvic multiparametric MRI in men with biochemically recurrent prostate cancer. Materials and Methods Men were prospectively recruited after prostatectomy and/or radiation therapy with rising prostate-specific antigen level (median, 2.27 ng/mL; range, 0.2-27.45 ng/mL) and a negative result at conventional imaging (bone scan and/or CT). Participants underwent 18F-DCFPyL PET/CT imaging and 3.0-T pelvic multiparametric MRI. Statistical analysis included Wald and modified χ2 tests. Results A total of 323 lesions were visualized in 77 men by using 18F-DCFPyL or multiparametric MRI, with imaging detection concordance of 25% (82 of 323) when including all lesions in the MRI field of view and 53% (52 of 99) when only assessing prostate bed lesions. 18F-DCFPyL depicted more pelvic lymph nodes than did MRI (128 vs 23 nodes). Histologic validation was obtained in 80 locations with sensitivity, specificity, and PPV of 69% (25 of 36; 95% confidence interval [CI]: 51%, 88%), 91% (40 of 44; 95% CI: 74%, 98%), and 86% (25 of 29; 95% CI: 73%, 97%) for 18F-DCFPyL and 69% (24 of 35; 95% CI: 50%, 86%), 74% (31 of 42; 95% CI: 42%, 89%), and 69% (24 of 35; 95% CI: 50%, 88%) for multiparametric MRI (P = .95, P = .14, and P = .07, respectively). In the prostate bed, sensitivity, specificity, and PPV were 57% (13 of 23; 95% CI: 32%, 81%), 86% (18 of 21; 95% CI: 73%, 100%), and 81% (13 of 16; 95% CI: 59%, 100%) for 18F-DCFPyL and 83% (19 of 23; 95% CI: 59%, 100%), 52% (11 of 21; 95% CI: 29%, 74%), and 66% (19 of 29; 95% CI: 44%, 86%) for multiparametric MRI (P = .19, P = .02, and P = .17, respectively). The addition of 18F-DCFPyL to multiparametric MRI improved PPV by 38% overall (P = .02) and by 30% (P = .09) in the prostate bed. Conclusion Findings with 2-(3-{1-carboxy-5-[(6-[18F]fluoro-pyridine 3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (18F-DCFPyL) were histologically validated and demonstrated high specificity and positive predictive value. In the pelvis, 18F-DCFPyL depicted more lymph nodes and improved positive predictive value and specificity when added to multiparametric MRI. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Zukotynski and Rowe in this issue.

Impact of bowel preparation with Fleet's™ enema on prostate MRI quality.

AIM: To investigate the effects of cleansing Fleet's™ enema (FE) on rectal distention and image quality of diffusion-weighted imaging (DWI) in prostate magnetic resonance imaging (MRI). METHODS: This study included 117 prospectively accrued active surveillance patients who underwent prostate MRI both without (prep-) and with bowel preparation consisting of FE (prep+) obtained within 12 months of each other. The anterior-posterior (AP) diameter of the rectum, degree of perceived distention in the rectum and image quality scores were assessed by two independent readers for both (prep- and prep+) scans. DWI distortion was assessed quantitatively using the degree of anatomic mismatches between images obtained at different b values and the T2-weighted MRI. DWI artifact was qualitatively scored based on the presence of blurring, poor signal-to-noise, and artifact lines. The difference in rectal AP diameters between the two methods was tested by the paired Wilcoxon rank test. Stuart Maxell test was used in comparing rectal distention, DWI distortion, and artifact. Reader agreement was estimated by kappa statistics. p values < 0.05 were considered statistically significant. RESULTS: Mean rectal AP diameter was significantly larger in prep- compared with prep+ scans (p = 0.002). Subjective scores demonstrated inter-reader variability. For instance, the rectal distention score was significantly lower in prep+ for reader 2 (p < 0.001) whereas it was not significant for reader 1 (p = 0.09). Reader 2 also found significant improvement in DWI distortion (p = 0.02) in prep+ scans. There was no significant difference between prep- and prep+ in DWI distortion and artifacts for reader 1 (p = 0.17 and p = 0.49, respectively), or DWI artifacts for reader 2 (p = 0.55). Kappa scores were moderate for rectal distension, but weak for DWI distortion, and artifacts. CONCLUSION: Bowel preparation with enema prior to prostate MRI may diminish rectal gas but has modest effects on DWI distortion and overall image quality. The value of bowel prep is not conclusively validated in this study.

Real-time fluorescence imaging for visualization and drug uptake prediction during drug delivery by thermosensitive liposomes.

Objective: Thermosensitive liposomal doxorubicin (TSL-Dox) is a promising stimuli-responsive nanoparticle drug delivery system that rapidly releases the contained drug in response to hyperthermia (HT) (>40 °C). Combined with localized heating, TSL-Dox allows highly localized delivery. The goals of this study were to demonstrate that real-time fluorescence imaging can visualize drug uptake during delivery, and can predict tumor drug uptake. Methods: Nude mice carrying subcutaneous tumors (Lewis lung carcinoma) were anesthetized and injected with TSL-Dox (5 mg/kg dose). Localized HT was induced by heating tumors for 15, 30 or 60 min via a custom-designed HT probe placed superficially at the tumor location. In vivo fluorescence imaging (excitation 523 nm, emission 610 nm) was performed before, during, and for 5 min following HT. After imaging, tumors were extracted, drug uptake was quantified by high-performance liquid chromatography, and correlated with in vivo fluorescence. Plasma samples were obtained before and after HT to measure TSL-Dox pharmacokinetics. Results: Local drug uptake could be visualized in real-time during HT. Compared to unheated control tumors, fluorescence of heated tumors increased by 4.6-fold (15 min HT), 9.3-fold (30 min HT), and 13.2-fold (60 min HT). HT duration predicted tumor drug uptake (p = .02), with tumor drug concentrations of 4.2 ± 1.3 µg/g (no HT), 7.1 ± 5.9 µg/g (15 min HT), 14.1 ± 6.7 µg/g (30 min HT) and 21.4 ± 12.6 µg/g (60 min HT). There was good correlation (R2 = 0.67) between fluorescence of the tumor region and tumor drug uptake. Conclusions: Real-time in vivo fluorescence imaging can visualize drug uptake during delivery, and can predict tumor drug uptake.

Drug release kinetics of temperature sensitive liposomes measured at high-temporal resolution with a millifluidic device.

PURPOSE: Current release assays have inadequate temporal resolution ( ∼ 10 s) to characterise temperature sensitive liposomes (TSL) designed for intravascular triggered drug release, where release within the first few seconds is relevant for drug delivery. MATERIALS AND METHODS: We developed a novel release assay based on a millifluidic device. A 500 µm capillary tube was heated by a temperature-controlled Peltier element. A TSL solution encapsulating a fluorescent compound was pumped through the tube, producing a fluorescence gradient along the tube due to TSL release. Release kinetics were measured by analysing fluorescence images of the tube. We measured three TSL formulations: traditional TSL (DPPC:DSPC:DSPE-PEF2000,80:15:5), MSPC-LTSL (DPPC:MSPC:DSPE-PEG2000,85:10:5) and MPPC-LTSL (DPPC:MMPC:PEF2000,86:10:4). TSL were loaded with either carboxyfluorescein (CF), Calcein, tetramethylrhodamine (TMR) or doxorubicin (Dox). TSL were diluted in one of the four buffers: phosphate buffered saline (PBS), 10% bovine serum albumin (BSA) solution, foetal bovine serum (FBS) or human plasma. Release was measured between 37-45 °C. RESULTS: The millifluidic device allowed measurement of release kinetics within the first few seconds at ∼5 ms temporal resolution. Dox had the fastest release and highest release %, followed by CF, Calcein and TMR. Of the four buffers, release was fastest in human plasma, followed by FBS, BSA and PBS. CONCLUSIONS: The millifluidic device allows measurement of TSL release at unprecedented temporal resolution, thus allowing adequate characterisation of TSL release at time scales relevant for intravascular triggered drug release. The type of buffer and encapsulated compound significantly affect release kinetics and need to be considered when designing and evaluating novel TSL-drug combinations.

Prostate Cancer: A Correlative Study of Multiparametric MR Imaging and Digital Histopathology.

Purpose To correlate multiparametric magnetic resonance (MR) imaging and quantitative digital histopathologic analysis (DHA) of the prostate. Materials and Methods This retrospective study was approved by the local institutional review board and was HIPAA compliant. Forty patients (median age, 60 years; age range, 44-71 years) who underwent prostate MR imaging consisting of T2-weighted and diffusion-weighted (DW) MR imaging along with subsequent robot-assisted radical prostatectomy gave informed consent to be included. Whole-mount tissue specimens were obtained with a patient-specific mold, and DHA was performed to assess the lumen, epithelium, stroma, and epithelial nucleus. These DHA images were registered with MR images and were correlated on a per-voxel basis. The relationship between MR imaging and DHA was assessed by using a linear mixed-effects model and the Pearson correlation coefficient. Results T2-weighted MR imaging, apparent diffusion coefficient (ADC) of DW imaging, and high-b-value DW imaging were significantly related to specific DHA parameters (P < .01). For instance, lumen density (ie, the percentage area of tissue components) was associated with T2-weighted MR imaging (slope = 0.36 ± 0.05 [standard error], γ = 0.35), ADC (slope = 0.47 ± 0.05, γ = 0.50), and high-b-value DW imaging (slope = -0.44 ± 0.05, γ = -0.44). Differences between regions harboring benign tissue and those harboring malignant tissue were observed at MR imaging and DHA (P < .01). Gleason score was significantly associated with MR imaging and DHA parameters (P < .05). For example, it was positively related to high-b-value DW imaging (slope = 0.21 ± 0.16, γ = 0.18) and negatively related to lumen density (slope = -0.19 ± 0.18, γ = -0.35). Conclusion Overall, significant associations were observed between MR imaging and DHA, regardless of prostate anatomy. © RSNA, 2017 Online supplemental material is available for this article.

Lyso-thermosensitive liposomal doxorubicin for treatment of bladder cancer.

PURPOSE: To evaluate lyso-thermosensitive liposomal doxorubicin (LTLD, ThermoDox®) in combination with loco-regional mild hyperthermia (HT) for targeted drug delivery to the bladder wall and potential treatment of bladder cancer. MATERIAL AND METHODS: Porcine in vivo studies were performed with the following groups: (i) intravenous (IV) LTLD with hyperthermia (LTLD + HT); (ii) IV doxorubicin (DOX) with hyperthermia (IV DOX + HT) and (iii) IV LTLD without hyperthermia (LTLD - HT). Drug formulations were delivered via 30 min IV infusion coinciding with 1-h bladder irrigation (45 °C water for HT groups, 37 °C for non-HT group), followed by immediate bladder resection. DOX concentrations were measured in consecutive sections parallel to the bladder lumen by liquid chromatography following drug extraction. Computer models were developed to simulate tissue heating and drug release from LTLD. RESULTS: Comparing mean DOX concentrations at increasing depths from the lumen to outer surface of the bladder wall, the ranges for LTLD + HT, IV DOX + HT and LTLD - HT, respectively, were 20.32-3.52 µg/g, 2.34-0.61 µg/g and 2.18-0.51 µg/g. The average DOX concentrations in the urothelium/lamina and muscularis, respectively, were 9.7 ± 0.67 and 4.09 ± 0.81 µg/g for IV LTLD + HT, 1.2 ± 0.39 and 0.86 ± 0.24 µg/g for IV DOX + HT, and 1.15 ± 0.38 and 0.62 ± 0.15 µg/g for LTLD - HT. Computational model results were similar to measured DOX levels and suggest adequate temperatures were reached within the bladder wall for drug release from LTLD. CONCLUSIONS: Doxorubicin accumulation and distribution within the bladder wall was achieved at concentrations higher than with free IV doxorubicin by mild bladder hyperthermia combined with systemic delivery of LTLD.

Biodistribution and Efficacy of Low Temperature-Sensitive Liposome Encapsulated Docetaxel Combined with Mild Hyperthermia in a Mouse Model of Prostate Cancer.

PURPOSE: Low temperature sensitive liposome (LTSL) encapsulated docetaxel were combined with mild hyperthermia (40-42°C) to investigate in vivo biodistribution and efficacy against a castrate resistant prostate cancer. METHOD: Female athymic nude mice with human prostate PC-3 M-luciferase cells grown subcutaneously into the right hind leg were randomized into six groups: saline (+/- heat), free docetaxel (+/- heat), and LTSL docetaxel (+/- heat). Treatment (15 mg docetaxel/kg) was administered via tail vein once tumors reached a size of 200-300 mm(3). Mice tumor volumes and body weights were recorded for up to 60 days. Docetaxel concentrations of harvested tumor and organ/tissue homogenates were determined by LC-MS. Histological evaluation (Mean vessel density, Ki67 proliferation, Caspase-3 apoptosis) of saline, free Docetaxel and LTSL docetaxel (+/- heat n = 3-5) was performed to determine molecular mechanism responsible for tumor cell killing. RESULT: LTSL/heat resulted in significantly higher tumor docetaxel concentrations (4.7-fold greater compared to free docetaxel). Adding heat to LTSL Docetaxel or free docetaxel treatment resulted in significantly greater survival and growth delay compared to other treatments (p < 0.05). Differences in body weight between all Docetaxel treatments were not reduced by >10% and were not statistically different from each other. Molecular markers such as caspase-3 were upregulated, and Ki67 expression was significantly decreased in the chemo-hyperthermia group. Vessel density was similar post treatment, but the heated group had reduced vessel area, suggesting thermal enhancement in efficacy by reduction in functional perfusion. CONCLUSION: This technique of hyperthermia sensitization and enhanced docetaxel delivery has potential for clinical translation for prostate cancer treatment.

Thermochromic tissue-mimicking phantom for optimisation of thermal tumour ablation.

Purpose The purpose of this study was to (1) develop a novel tissue-mimicking thermochromic (TMTC) phantom that permanently changes colour from white to magenta upon heating above ablative temperatures, and (2) assess its utility for specific applications in evaluating thermal therapy devices. Materials and methods Polyacrylamide gel mixed with thermochromic ink was custom made to produce a TMTC phantom that changes its colour upon heating above biological ablative temperatures (> 60 °C). The thermal properties of the phantom were characterised, and compared to those of human tissue. In addition, utility of this phantom as a tool for the assessment of laser and microwave thermal ablation was examined. Results The mass density, thermal conductivity, and thermal diffusivity of the TMTC phantom were measured as 1033 ± 1.0 kg/m(3), 0.590 ± 0.015 W/m.K, and 0.145 ± 0.002 mm(2)/s, respectively, and found to be in agreement with reported values for human soft tissues. Heating the phantom with laser and microwave ablation devices produced clearly demarcated regions of permanent colour change geographically corresponding to regions with temperature elevations above 60 °C. Conclusion The TMTC phantom provides direct visualisation of ablation dynamics, including ablation volume and geometry as well as peak absolute temperatures within the treated region post-ablation. This phantom can be specifically tailored for different thermal therapy modalities, such as radiofrequency, laser, microwave, or therapeutic ultrasound ablation. Such modality-specific phantoms may enable better quality assurance, device characterisation, and ablation parameter optimisation, or optimise the study of dynamic heating parameters integral to drug device combination therapies relying upon heat.

A Novel Inherently Radiopaque Bead for Transarterial Embolization to Treat Liver Cancer - A Pre-clinical Study.

PURPOSE: Embolotherapy using microshperes is currently performed with soluble contrast to aid in visualization. However, administered payload visibility dimishes soon after delivery due to soluble contrast washout, leaving the radiolucent bead's location unknown. The objective of our study was to characterize inherently radiopaque beads (RO Beads) in terms of physicomechanical properties, deliverability and imaging visibility in a rabbit VX2 liver tumor model. MATERIALS AND METHODS: RO Beads, which are based on LC Bead® platform, were compared to LC Bead. Bead size (light microscopy), equilibrium water content (EWC), density, X-ray attenuation and iodine distribution (micro-CT), suspension (settling times), deliverability and in vitro penetration were investigated. Fifteen rabbits were embolized with either LC Bead or RO Beads + soluble contrast (iodixanol-320), or RO Beads+dextrose. Appearance was evaluated with fluoroscopy, X-ray single shot, cone-beam CT (CBCT). RESULTS: Both bead types had a similar size distribution. RO Beads had lower EWC (60-72%) and higher density (1.21-1.36 g/cc) with a homogeneous iodine distribution within the bead's interior. RO Beads suspension time was shorter than LC Bead, with durable suspension (>5 min) in 100% iodixanol. RO Beads ≤300 µm were deliverable through a 2.3-Fr microcatheter. Both bead types showed similar penetration. Soluble contrast could identify target and non-target embolization on fluoroscopy during administration. However, the imaging appearance vanished quickly for LC Bead as contrast washed-out. RO Beads+contrast significantly increased visibility on X-ray single shot compared to LC Bead+contrast in target and non-target arteries (P=0.0043). Similarly, RO beads demonstrated better visibility on CBCT in target arteries (P=0.0238) with a trend in non-target arteries (P=0.0519). RO Beads+dextrose were not sufficiently visible to monitor embolization using fluoroscopy. CONCLUSION: RO Beads provide better conspicuity to determine target and non-target embolization compared to LC Bead which may improve intra-procedural monitoring and post-procedural evaluation of transarterial embolization.

Multimodality Imaging of Ethiodized Oil-loaded Radiopaque Microspheres during Transarterial Embolization of Rabbits with VX2 Liver Tumors.

Purpose To assess the visibility of radiopaque microspheres during transarterial embolization (TAE) in the VX2 rabbit liver tumor model by using multimodality imaging, including single-snapshot radiography, cone-beam computed tomography (CT), multidetector CT, and micro-CT. Materials and Methods The study was approved by the institutional animal care and use committee. Fifteen VX2-tumor-bearing rabbits were assigned to three groups depending on the type of embolic agent injected: 70-150-µm radiopaque microspheres in saline (radiopaque microsphere group), 70-150-µm radiopaque microspheres in contrast material (radiopaque microsphere plus contrast material group), and 70-150-µm radiolucent microspheres in contrast material (nonradiopaque microsphere plus contrast material group). Rabbits were imaged with single-snapshot radiography, cone-beam CT, and multidetector CT. Three to 5 weeks after sacrifice, excised livers were imaged with micro-CT and histologic analysis was performed. The visibility of the embolic agent was assessed with all modalities before and after embolization by using a qualitative three-point scale score reading study and a quantitative assessment of the signal-to-noise ratio (SNR) change in various regions of interest, including the tumor and its feeding arteries. The Kruskal-Wallis test was used to compare the rabbit characteristics across groups, and the Wilcoxon signed rank test was used to compare SNR measurements before and after embolization. Results Radiopaque microspheres were qualitatively visualized within tumor feeding arteries and targeted tissue with all imaging modalities (P < .05), and their presence was confirmed with histologic examination. SNRs of radiopaque microsphere deposition increased after TAE on multidetector CT, cone-beam CT, and micro-CT images (P < .05). Similar results were obtained when contrast material was added to radiopaque microspheres, except for additional image attenuation due to tumor enhancement. For the group with nonradiopaque microspheres and contrast material, retained tumoral contrast remained qualitatively visible with all modalities except for micro-CT, which demonstrated soluble contrast material washout over time. Conclusion Radiopaque microspheres were visible with all imaging modalities and helped increase conspicuity of the tumor as well as its feeding arteries after TAE in a rabbit VX2 liver tumor model. (©) RSNA, 2015.

Preparation of Radiopaque Drug-Eluting Beads for Transcatheter Chemoembolization.

PURPOSE: To develop a simple method to produce radiopaque drug-eluting microspheres (drug-eluting beads [DEBs]) that could be incorporated into the current clinical transcatheter arterial chemoembolization workflow and evaluate their performance in vitro and in vivo. MATERIALS AND METHODS: An ethiodized oil (Lipiodol; Guerbet, Villepinte, France) and ethanol solution was added to a lyophilized 100-300 µm bead before loading with doxorubicin. These radiopaque drug-eluting beads (DEBs; Biocompatibles UK Ltd, Farnham, United Kingdom) were evaluated in vitro for x-ray attenuation, composition, size, drug loading and elution, and correlation between attenuation and doxorubicin concentration. In vivo conspicuity was evaluated in a VX2 tumor model. RESULTS: Lipiodol was loaded into lyophilized beads using two glass syringes and a three-way stopcock. Maximum bead attenuation was achieved within 30 minutes. X-ray attenuation of radiopaque beads increased linearly (21-867 HU) with the amount of beads (0.4-12.5 vol%; R(2) = 0.9989). Doxorubicin loading efficiency and total amount eluted were similar to DC Bead (Biocompatibles UK Ltd); however, the elution rate was slower for radiopaque DEBs (P < .05). Doxorubicin concentration linearly correlated with x-ray attenuation of radiopaque DEBs (R(2) = 0. 99). Radiopaque DEBs were seen in tumor feeding arteries after administration by fluoroscopy, computed tomography, and micro-computed tomography, and their location was confirmed by histology. CONCLUSIONS: A simple, rapid method to produce radiopaque DEBs was developed. These radiopaque DEBs provided sufficient conspicuity to be visualized with x-ray imaging techniques.

Temperature-sensitive liposome-mediated delivery of thrombolytic agents.

BACKGROUND: Clinical efficacy of thrombolytic drugs is limited by lack of specific delivery and requires large therapeutic doses which increase toxicity. Encapsulating these drugs in temperature-sensitive liposomes and applying hyperthermia to deliver thrombolytic agents locally to thrombus might theoretically favourably alter the therapeutic window. The objectives of this study were to formulate liposomes encapsulating thrombolytics and assess thrombolytic activity following hyperthermia. METHODS: Three liposome formulations were investigated: temperature-sensitive liposome (TSL, DPPC:DSPE-PEG2000 (mol% 95:5)), low temperature-sensitive liposome (LTSL, DPPC:MSPC:DSPE-PEG2000 (mol% 85.3:9.7:5)), and traditional temperature-sensitive liposome (TTSL, DPPC:HSPC:Chol:DSPE-PEG2000 (mol% 55:25:15:5)). To characterise temperature-dependent release of high molecular weight cargo from each formulation, fluorescein-conjugated dextrans (70 kDa) were loaded and release was quantified via spectrophotometry. Staphylokinase (SAK), urokinase, and tissue-type plasminogen activator were also loaded individually into each liposome formulation. Leakage at 37 °C and release at 38-44 °C were quantified via chromogenic enzymatic activity assay. Clot lysis was evaluated by measuring mass of blood clots before and after thrombolytic liposome treatment. RESULTS: The LTSL formulation had optimal release characteristics with maximum release at 41.3 °C. Release of dextrans from LTSLs was observed to be 11.5 ± 1.5%, 79.7 ± 1.6%, and 93.6 ± 3.7% after 15 min in plasma at 37°, 39°, and 41.3 °C, respectively. The SAK LTSL had the highest release/leakage ratio and demonstrated greater clot lysis. CONCLUSIONS: The SAK LTSL achieves significant clot lysis in vitro. When combined with local hyperthermia, the SAK LTSL potentially produces sufficient thrombolysis while minimising systemic side effects.

Magnetic resonance imaging (MRI)-guided transurethral ultrasound therapy of the prostate: a preclinical study with radiological and pathological correlation using customised MRI-based moulds.

OBJECTIVE: To characterise the feasibility and safety of a novel transurethral ultrasound (US)-therapy device combined with real-time multi-plane magnetic resonance imaging (MRI)-based temperature monitoring and temperature feedback control, to enable spatiotemporally precise regional ablation of simulated prostate gland lesions in a preclinical canine model. To correlate ablation volumes measured with intra-procedural cumulative thermal damage estimates, post-procedural MRI, and histopathology. MATERIALS AND METHODS: Three dogs were treated with three targeted ablations each, using a prototype MRI-guided transurethral US-therapy system (Philips Healthcare, Vantaa, Finland). MRI provided images for treatment planning, guidance, real-time multi-planar thermometry, as well as post-treatment evaluation of efficacy. After treatment, specimens underwent histopathological analysis to determine the extent of necrosis and cell viability. Statistical analyses (Pearson's correlation, Student's t-test) were used to evaluate the correlation between ablation volumes measured with intra-procedural cumulative thermal damage estimates, post-procedural MRI, and histopathology. RESULTS: MRI combined with a transurethral US-therapy device enabled multi-planar temperature monitoring at the target as well as in surrounding tissues, allowing for safe, targeted, and controlled ablations of prescribed lesions. Ablated volumes measured by cumulative thermal dose positively correlated with volumes determined by histopathological analysis (r(2) 0.83, P < 0.001). Post-procedural contrast-enhanced and diffusion-weighted MRI showed a positive correlation with non-viable areas on histopathological analysis (r(2) 0.89, P < 0.001, and r(2) 0.91, P = 0.003, respectively). Additionally, there was a positive correlation between ablated volumes according to cumulative thermal dose and volumes identified on post-procedural contrast-enhanced MRI (r(2) 0.77, P < 0.01). There was no difference in mean ablation volumes assessed with the various analysis methods (P > 0.05, Student's t-test). CONCLUSIONS: MRI-guided transurethral US therapy enabled safe and targeted ablations of prescribed lesions in a preclinical canine prostate model. Ablation volumes were reliably predicted by intra- and post-procedural imaging. Clinical studies are needed to confirm the feasibility, safety, oncological control, and functional outcomes of this therapy in patients in whom focal therapy is indicated.

Cytotoxicity of hepatocellular carcinoma cells to hyperthermic and ablative temperature exposures: in vitro studies and mathematical modelling.

PURPOSE: Image-guided ablative therapies use temperatures greater than 45 °C to kill abnormal cells. There is limited published data of cell survival after ablative temperature exposures, which is of importance to predict ablation zone dimensions. The objective of this study was to determine and mathematically model survival of hepatocellular carcinoma cells following ablative temperature exposures (45-60 °C). MATERIALS AND METHODS: Hepatocellular carcinoma (HCC) cell lines were plated in 96-well plates, and heated between 45 and 60 °C for 0-32 min. Heating was applied by a rapid media exchange with heated Hank's balanced salt solution (HBSS) in a temperature-controlled water bath. Cell viability was determined by MTS assay. Survival data was modelled by the Arrhenius model, and the thermal isoeffective dose (TID) model where kinetic parameters were determined via non-linear optimisation. RESULTS: Results suggest that the thermal dose based on cumulative equivalent minutes and parameters as used for hyperthermia exposures (<43 °C) is not applicable for ablative exposures. We found R = 0.72 for temperatures between 45-60°C for the TID model. The Arrhenius parameters were frequency factor A = 3.25E43 1/s, and activation energy Ea = 281 kJ/mol. These parameters correlate well with a prior study in the same cell line, and with threshold temperatures for necrosis from in vivo studies. CONCLUSIONS: Our results suggest that standard TID model kinetic parameters based on hyperthermia studies, often also used at ablation temperatures, are not applicable at these higher temperatures for HCC cells.

Translational predictive biomarker analysis of the phase 1b sorafenib and bevacizumab study expansion cohort.

Predictive biomarkers are needed to triage patients to the best therapy. We prospectively planned examination of sequential blood, biopsy, and functional imaging with which to confirm the mechanism and to identify potential predictive biomarkers in a phase Ib clinical trial expansion of patients with solid tumors receiving sorafenib/bevacizumab. The maximally tolerated doses of sorafenib at 200 mg twice daily with bevacizumab at 5 mg/kg every other week were given to biopsiable patients. Patients were randomized to receive either sorafenib or bevacizumab monotherapy for the first 28-day cycle with the second drug added with cycle 2. Biopsies, dynamic contrast-enhanced MRI, and fluorodeoxyglucose-proton emission tomography were done pre-therapy and at 2 and 6 weeks (2 weeks into combination therapy). Tumor and serum proteomics, Ras/Raf mutational analysis, and functional imaging results were examined individually and across the dataset to identify potential changes predictive of response to therapy and those that confirm the biochemical drug mechanism(s). Therapy with sorafenib/bevacizumab resulted in clinical benefit in 45% of this mixed solid tumor group. ERK activation and microvessel density were decreased with monotherapy treatment with sorafenib or bevacizumab, respectively; whereas a decreased signal over the group of total AKT, phospho(p)-VEGF receptor2, p-endothelial nitric-oxide synthase, b-RAF, and cleaved poly(ADP-ribose) polymerase was associated with earlier progression of disease. Tumor metabolic activity decreased in those patients with clinical benefits lasting longer than 4 months, and activity increased with progression of disease. Cleavage of caspase 3 and poly(ADP-ribose) polymerase was increased, and Ki67 expression decreased in patients with prolonged clinical benefits, consistent with decreased proliferation and increased apoptosis. The conglomerate analysis, incorporating pharmacodynamic and tumor biochemistry, demonstrated sorafenib/bevacizumab-targeted vascular activity in the tumor. Results suggest potential biomarkers for which changes, as a group, during early therapeutic exposure may predict clinical benefit.

Reduction of peak acoustic pressure and shaping of heated region by use of multifoci sonications in MR-guided high-intensity focused ultrasound mediated mild hyperthermia.

PURPOSE: Ablative hyperthermia (>55 °C) has been used as a definitive treatment for accessible solid tumors not amenable to surgery, whereas mild hyperthermia (40-45 °C) has been shown effective as an adjuvant for both radiotherapy and chemotherapy. An optimal mild hyperthermia treatment is spatially accurate, with precise and homogeneous heating limited to the target region while also limiting the likelihood of unwanted thermal or mechanical bioeffects (tissue damage, vascular shutoff). Magnetic resonance imaging-guided high-intensity focused ultrasound (MR-HIFU) can noninvasively heat solid tumors under image-guidance. In a mild hyperthermia setting, a sonication approach utilizing multiple concurrent foci may provide the benefit of reducing acoustic pressure in the focal region (leading to reduced or no mechanical effects), while providing better control over the heating. The objective of this study was to design, implement, and characterize a multifoci sonication approach in combination with a mild hyperthermia heating algorithm, and compare it to the more conventional method of electronically sweeping a single focus. METHODS: Simulations (acoustic and thermal) and measurements (acoustic, with needle hydrophone) were performed. In addition, heating performance of multifoci and single focus sonications was compared using a clinical MR-HIFU platform in a phantom (target = 4-16 mm), in normal rabbit thigh muscle (target = 8 mm), and in a Vx2 tumor (target = 8 mm). A binary control algorithm was used for real-time mild hyperthermia feedback control (target range = 40.5-41 °C). Data were analyzed for peak acoustic pressure and intensity, heating energy efficiency, temperature accuracy (mean), homogeneity of heating (standard deviation [SD], T10 and T90), diameter and length of the heated region, and thermal dose (CEM(43)). RESULTS: Compared to the single focus approach, multifoci sonications showed significantly lower (67% reduction) peak acoustic pressures in simulations and hydrophone measurements. In a rabbit Vx2 tumor, both single focus and multifoci heating approaches were accurate (mean = 40.82±0.12 °C [single] and 40.70±0.09 °C [multi]) and precise (standard deviation = 0.65±0.05 °C [single] and 0.64±0.04 °C [multi]), producing homogeneous heating (T(10-90) = 1.62 °C [single] and 1.41 °C [multi]). Heated regions were significantly shorter in the beam path direction (35% reduction, p < 0.05, Tukey) for multifoci sonications, i.e., resulting in an aspect ratio closer to one. Energy efficiency was lower for the multifoci approach. Similar results were achieved in phantom and rabbit muscle heating experiments. CONCLUSIONS: A multifoci sonication approach was combined with a mild hyperthermia heating algorithm, and implemented on a clinical MR-HIFU platform. This approach resulted in accurate and precise heating within the targeted region with significantly lower acoustic pressures and spatially more confined heating in the beam path direction compared to the single focus sonication method.The reduction in acoustic pressure and improvement in spatial control suggest that multifoci heating is a useful tool in mild hyperthermia applications for clinical oncology.

Low suspicion lesions on multiparametric magnetic resonance imaging predict for the absence of high-risk prostate cancer.

UNLABELLED: What's known on the subject? and What does the study add? Over-treatment of indolent prostate cancer lesions is a problem which can result in increased human and medical costs. Lesions with a low suspician level at mpMRI of the prostate have low risk of including high risk prostate cancer. OBJECTIVE: To determine whether multiparametric magnetic resonance imaging (mpMRI) has the potential to identify patients at low risk for cancer, thus obviating the need for biopsy. Prostate cancer is currently diagnosed by random biopsies, resulting in the discovery of multiple low-risk cancers that often lead to overtreatment. PATIENTS AND METHODS: We reviewed 800 consecutive patients who underwent a 3 Tesla mpMRI of the prostate with an endorectal coil from March 2007 to November 2011. All suspicious lesions were independently reviewed by two radiologists using T2-weighted, diffusion-weighted, spectroscopic and dynamic contrast-enhanced MRI sequences. Patients with only low suspicion lesions (maximum of two positive parameters on mpMRI) who subsequently underwent transrectal ultrasonography (TRUS)/MRI fusion targeted biopsy were selected for analysis. RESULTS: In total, 125 patients with only low suspicion prostatic lesions on mpMRI were identified. On TRUS/MRI fusion biopsy, 77 (62%) of these patients had no cancer detected, 38 patients had Gleason 6 disease and 10 patients had Gleason 7 (3+4) disease. There were 30 patients with cancer detected on biopsy who qualified for active surveillance using 2011 National Comprehensive Cancer Network guidelines. No cases of high-risk (≥ Gleason 4+3) cancer were identified on biopsy and, of the fifteen patients who underwent radical prostatectomy at our institution, none were pathologically upgraded to high-risk cancer. Thus, for patients with only low suspicion lesions, 107 (88%) patients either had no cancer or clinically insignificant disease. CONCLUSIONS: The results obtained in the present study show that low suspicion lesions on mpMRI are associated with either negative biopsies or low-grade tumours suitable for active surveillance. Such patients have a low risk of harbouring high-risk prostate cancers.

Mild hyperthermia with magnetic resonance-guided high-intensity focused ultrasound for applications in drug delivery.

PURPOSE: Mild hyperthermia (40-45 °C) is a proven adjuvant for radiotherapy and chemotherapy. Magnetic resonance guided high intensity focused ultrasound (MR-HIFU) can non-invasively heat solid tumours under image guidance. Low temperature-sensitive liposomes (LTSLs) release their drug cargo in response to heat (>40 °C) and may improve drug delivery to solid tumours when combined with mild hyperthermia. The objective of this study was to develop and implement a clinically relevant MR-HIFU mild hyperthermia heating algorithm for combination with LTSLs. MATERIALS AND METHODS: Sonications were performed with a clinical MR-HIFU platform in a phantom and rabbits bearing VX2 tumours (target = 4-16 mm). A binary control algorithm was used for real-time mild hyperthermia feedback control (target = 40-41 °C). Drug delivery with LTSLs was measured with HPLC. Data were compared to simulation results and analysed for spatial targeting accuracy (offset), temperature accuracy (mean), homogeneity of heating (standard deviation (SD), T10 and T90), and thermal dose (CEM43). RESULTS: Sonications in a phantom resulted in better temperature control than in vivo. Sonications in VX2 tumours resulted in mean temperatures between 40.4 °C and 41.3 °C with a SD of 1.0-1.5 °C (T10 = 41.7-43.7 °C, T90 = 39.0-39.6 °C), in agreement with simulations. 3D spatial offset was 0.1-3.2 mm in vitro and 0.6-4.8 mm in vivo. Combination of MR-HIFU hyperthermia and LTSLs demonstrated heterogeneous delivery to a partially heated VX2 tumour, as expected. CONCLUSIONS: An MR-HIFU mild hyperthermia heating algorithm was developed, resulting in accurate and homogeneous heating within the targeted region in vitro and in vivo, which is suitable for applications in drug delivery.

Targeted drug delivery by high intensity focused ultrasound mediated hyperthermia combined with temperature-sensitive liposomes: computational modelling and preliminary in vivovalidation.

PURPOSE: To develop and validate a computational model that simulates (1) tissue heating with high intensity focused ultrasound (HIFU), and (2) resulting hyperthermia-mediated drug delivery from temperature-sensitive liposomes (TSL). MATERIALS AND METHODS: HIFU heating in tissue was simulated using a heat transfer model based on the bioheat equation, including heat-induced cessation of perfusion. A spatio-temporal multi-compartment pharmacokinetic model simulated intravascular release of doxorubicin from TSL, its transport into interstitium, and cell uptake. Two heating schedules were simulated, each lasting 30 min: (1) hyperthermia at 43 °C (HT) and (2) hyperthermia followed by a high temperature (50 °C for 20 s) pulse (HT+). As preliminary model validation, in vivo studies were performed in thigh muscle of a New Zealand White rabbit, where local hyperthermia with a clinical magnetic resonance-guided HIFU system was applied following TSL administration. RESULTS: HT produced a defined region of high doxorubicin concentration (cellular concentration ∼15-23 µg/g) in the target region. Cellular drug uptake was directly related to HT duration, with increasing doxorubicin uptake up to ∼2 h. HT+ enhanced drug delivery by ∼40% compared to HT alone. Temperature difference between model and experiment within the hyperthermia zone was on average 0.54 °C. Doxorubicin concentration profile agreed qualitatively with in vivo fluorescence profile. CONCLUSIONS: Computational models can predict temperature and delivered drug from combination of HIFU with TSL. Drug delivery using TSL may be enhanced by prolonged hyperthermia up to 2 h or by local cessation of vascular perfusion with a high temperature pulse following hyperthermia.