Sergio Dromi

Pulsed-High Intensity Focused Ultrasound and Low Temperature– Sensitive Liposomes for Enhanced Targeted Drug Delivery and Antitumor Effect

Purpose: To determine if pulsed-high intensity focused ultrasound (HIFU) could effectively serve as a source of hyperthermia with thermosensitive liposomes to enhance delivery and efficacy of doxorubicin in tumors. Experimental Design: Comparisons in vitro and in vivo were carried out between non–thermosensitive liposomes (NTSL) and low temperature–sensitive liposomes (LTSL). Liposomes were incubated in vitro over a range of temperatures and durations, and the amount of doxorubicin released was measured. For in vivo experiments, liposomes and free doxorubicin were injected i.v. in mice followed by pulsed-HIFU exposures in s.c. murine adenocarcinoma tumors at 0 and 24 h after administration. Combinations of the exposures and drug formulations were evaluated for doxorubicin concentration and growth inhibition in the tumors. Results:In vitro incubations simulating the pulsed-HIFU thermal dose (42°C for 2 min) triggered release of 50% of doxorubicin from the LTSLs; however, no detectable release from the NTSLs was observed. Similarly, in vivo experiments showed that pulsed-HIFU exposures combined with the LTSLs resulted in more rapid delivery of doxorubicin as well as significantly higher i.t. concentration when compared with LTSLs alone or NTSLs, with or without exposures. Combining the exposures with the LTSLs also significantly reduced tumor growth compared with all other groups. Conclusions: Combining low-temperature heat-sensitive liposomes with noninvasive and nondestructive pulsed-HIFU exposures enhanced the delivery of doxorubicin and, consequently, its antitumor effects. This combination therapy could potentially produce viable clinical strategies for improved targeting and delivery of drugs for treatment of cancer and other diseases.

Phase I Study of Heat-Deployed Liposomal Doxorubicin during Radiofrequency Ablation for Hepatic Malignancies

PURPOSE A phase I dose escalation study was performed with systemically delivered lyso-thermosensitive liposomal doxorubicin (LTLD). The primary objectives were to determine the safe maximum tolerated dose (MTD), pharmacokinetic properties, and dose-limiting toxicity (DLT) of LTLD during this combination therapy. MATERIALS AND METHODS Subjects eligible for percutaneous or surgical radiofrequency (RF) ablation with primary (n = 9) or metastatic (n = 15) tumors of the liver, with four or fewer lesions as large as 7 cm in diameter, were included. RF ablation was initiated 15 minutes after starting a 30-minute intravenous LTLD infusion. Dose levels between 20 mg/m(2) and 60 mg/m(2) were evaluated. Magnetic resonance imaging, positron emission tomography, and computed tomography were performed at predetermined intervals before and after treatment until evidence of recurrence was seen, administration of additional antitumor treatment was performed, or a total of 3 years had elapsed. RESULTS DLT criteria were met at 60 mg/m(2), and the MTD was defined as 50 mg/m(2). RF ablation was performed during the peak of the plasma concentration-time curve in an effort to yield maximal drug deposition. LTLD produced reversible, dose-dependent neutropenia and leukopenia. CONCLUSIONS LTLD can be safely administered systemically at the MTD (50 mg/m(2)) in combination with RF ablation, with limited and manageable toxicity. Further evaluation of this agent combined with RF ablation is warranted to determine its role in the management of liver tumors.

Radiofrequency Ablation Induces Antigen-presenting Cell Infiltration and Amplification of Weak Tumor-induced Immunity

PURPOSE To evaluate the influence of subtotal radiofrequency (RF) ablation on a tumor-specific immune response in a murine tumor model and to explore the role of intratumoral dendritic cells (ITDCs) in mediating this effect. MATERIALS AND METHODS Animal work was performed according to an approved protocol and in compliance with the National Cancer Institute Animal Care and Use Committee guidelines and regulations. A murine urothelial carcinoma (MB49) model expressing the male minor histocompatibility (HY) antigen was inoculated subcutaneously in female mice. Fourteen days later, splenic T cells were analyzed with enzyme-linked immunosorbent spot for HY immune response (n = 57). In subsequent experiments, mice were randomized into control (n = 7), RF ablation, ITDC (n = 9), and RF ablation + ITDC (n = 9) groups and monitored for tumor growth. Eleven days after treatment, tumors were harvested for histologic and immunohistochemical analysis. Animals demonstrating complete tumor regression were rechallenged in the contralateral flank. RESULTS Animals treated with subtotal RF ablation showed significant increases in tumor-specific class I and II responses to HY antigens and tumor regression. RF ablation, ITDC, and combined groups demonstrated similar levels of antigen-presenting cell infiltration; all groups demonstrated greater levels of infiltration compared with untreated controls. ITDC injection also resulted in tumor regression. However, combination therapy did not enhance tumor regression when compared with either treatment alone. Rechallenged mice in RF ablation, ITDC, and combination groups demonstrated significant tumor growth inhibition compared with controls. CONCLUSION Subtotal RF ablation treatment results in enhanced systemic antitumor T-cell immune responses and tumor regression that is associated with increased dendritic cell infiltration. ITDC injection mimics the RF ablation effect but does not increase immune responses when injected immediately after RF ablation.

In vitro and in vivo evaluations of increased effective beam width for heat deposition using a split focus high intensity ultrasound (HIFU) transducer

Purpose: To develop a novel and efficient, in vitro method for characterizing temporal and spatial heat generation of focused ultrasound exposures, and evaluate this method to compare a split focus and conventional single focus high intensity focused ultrasound transducer. Materials and methods: A HIFU tissue-mimicking phantom was validated by comparing respective temperature elevations generated in the phantoms and in murine tumors in vivo. The phantom was then used in combination with IR thermography to spatially and temporally characterize differences in low-level temperature elevation (e.g. 3–5°C) produced by a single focus and split focus HIFU transducer, where the latter produces four simultaneous foci. In vivo experiments with heat sensitive liposomes containing doxorubicin were then carried out to determine if the larger beam width of the split focus transducer, compared to the single focus, could increase overall deployment of the drug from the liposome. Results: Temperature elevations generated in the HIFU phantom were not found to be different from those measured in vivo when compensating for disparities in attenuation coefficient and specific heat, and between the two transducers by increasing the energy deposition. Exposures with the split focus transducer provided significant increases in the area treated compared to the single focus, which then translated to significant increases in drug deposition in vivo. Conclusions: Preliminary evidence was provided indicating the potential for using this novel technique for characterizing hyperthermia produced by focused ultrasound devices. Further development will be required for its suitability for correlating in vitro and in vivo outcomes.

CT fluoroscopy shielding: decreases in scattered radiation for the patient and operator.

PURPOSE High-radiation exposure occurs during computed tomographic (CT) fluoroscopy. Patient and operator doses during thoracic and abdominal interventional procedures were studied in the present experiment, and a novel shielding device to reduce exposure to the patient and operator was evaluated. MATERIALS AND METHODS With a 16-slice CT scanner in CT fluoroscopy mode (120 kVp, 30 mA), surface dosimetry was performed on adult and pediatric phantoms. The shielding was composed of tungsten antimony in the form of a lightweight polymer sheet. Doses to the patient were measured with and without shielding for thoracic and abdominal procedures. Doses to the operator were recorded with and without phantom, gantry, and table shielding in place. Double-layer lead-free gloves were used by the operator during the procedures. RESULTS Tungsten antimony shielding adjacent to the scan plane resulted in a maximum dose reduction of 92.3% to the patient. Maximum 85.6%, 93.3%, and 85.1% dose reductions were observed for the operators torso, gonads, and hands, respectively. The use of double-layer lead-free gloves resulted in a maximum radiation dose reduction of 97%. CONCLUSIONS Methods to reduce exposure during CT fluoroscopy are effective and should be searched for. Significant reduction in radiation doses to the patient and operator can be accomplished with tungsten antimony shielding.

Heavy Metal Pad Shielding during Fluoroscopic Interventions

Significant direct and scatter radiation doses to patient and physician may result from routine interventional radiology practice. A lead-free disposable tungsten antimony shielding pad was tested in phantom patients during simulated diagnostic angiography procedures. Although the exact risk of low doses of ionizing radiation is unknown, dramatic dose reductions can be seen with routine use of this simple, sterile pad made from lightweight tungsten antimony material.

Pulsed-high intensity focused ultrasound (HIFU) exposures for enhanced delivery of therapeutics: Mechanisms and applications

The majority of focused ultrasound applications today involve long, continuous exposures that produce significant temperature elevations for tissue ablation and irreversible coagulative necrosis. Comparatively little has been done with non‐continuous (or, pulsed) exposures that can produce primarily mechanical effects with only minimal heat. Our investigations have shown that pulsed‐HIFU exposures can non‐invasively and non‐destructively enhance the delivery of both systemically and locally injected materials (e.g. imaging agents, optical probes, and plasmid DNA) in both normal and cancerous tissues. It is hypothesized that the enhancing effects are directly linked to tissue displacement from locally‐generated radiation forces. In normal tissue, it is thought that shear forces are produced between adjacent tissue regions experiencing non‐uniform displacement. The resulting strain opens cellular junctions in both the vasculature and the parenchyma, increasing extravasation and interstitial diffusion, respe...

Radiofrequency Cauterization: An Alternative to Reduce Post-biopsy Hemorrhage

As recently described in animals [1], we applied radiofrequency ablation (RFA) to clinical practice as a technique to reduce the risk of bleeding after biopsy of a highly vascular tumor. A 26-year-old man was admitted for renal core biopsy. Prior fine-needle biopsy of a left kidney mass and a supraclavicular lymph node showed renal cell carcinoma of unknown subtype. Repeat biopsy was performed to diagnose histologic subtype, which can affect experimental treatment options. The patient had first presented 6 months previously with a 6 cm palpable cervical lymph node, weight loss of 9 kg, and fatigue with no hematuria. The CT scan revealed extensive lymphadenopathy throughout his mediastinum and left periaortic region, and a 6 cm left kidney mass with three liver metastases. Laboratory values were normal. A bone scan did not show evidence of metastatic disease. Prior to biopsy, color Doppler ultrasound revealed a very vascular tumor with many large and small vessels throughout the tumor, suggesting increased risk of biopsy-related bleeding [3]. The patient underwent an ultrasound-guided coaxial core biopsy with a 17 gauge 10 cm outer needle and an 18 gauge 15 cm inner needle. Brisk bright red pulsatile blood was seen in the outer needle following removal of the inner core biopsy gun. The stylet was replaced as soon as the pulsatile bleeding was seen. Two grounding pads were rapidly applied to the patient’s thighs and the tissue ablation system was set up. Just prior to removal of the outer biopsy needle, a Radionics (Valleylab, Boulder, CO) RFA probe (20 cm with a 3 cm uninsulated tip) was placed, using tandem technique, immediately adjacent to the biopsy needle and to the same insertion depth, under direct ultrasound guidance. The outer needle was then removed from the patient and the RFA Cool Tip generator (Valleylab, Boulder, CO) was turned on. Tissue was heated to 95°C for about 90 sec during slow withdrawal of the RFA probe, without chilled saline perfusion. The generator was stopped as the uninsulated portion of the needle was withdrawn from the tumor capsule, but prior to crossing dermis. No sign of bleeding was evident by ultrasound 15 min following the procedure or by clinical criteria the day following the procedure. The patient remained clinically stable during and after the application of this technique. The patient did not complain of pain after the procedure. The pathology results showed clear cell carcinoma with papillary features. Five days later an excisional biopsy of a right arm tumor was performed. Results showed leiomyoma. Given the patient’s extensive family history of malignancy (the father had a rare eye adenocarcinoma; 5 of 9 of the father’s siblings had cancer, 2 of them renal cell carcinoma; and the mother’s siblings had renal cell carcinoma, uterine, and esophageal cancers) the diagnosis of hereditary leiomyomatosis renal cell carcinoma syndrome (HLRCC) was made. RFA may be a helpful therapeutic option to avoid the bleeding that may be seen in up to 90% of patients by CT [5] after a percutaneous renal biopsy, depending upon how one defines bleeding. Less than 3% of renal biopsies require transfusion or an intervention to stop the bleeding [6]. Other therapeutic options available are transarterial embolization with polyvinyl alcohol or acrylic particles, collagen pledgets, autologous blood, or metal coils [3]. These techniques, however, do not address the possibility of needle tract seeding with tumor cells, in contrast to RFA in which the tract is treated [4]. Also, treatment with embolization may result in an undesirable infarct in a patient with already compromised renal function. While RFA has been emerging as a viable therapeutic option for certain renal cell carcinomas and has a definitive success rate over 90% with few complications in selected patients [2, 4], it may be a low-risk, nephron-sparing method to facilitate hemostasis in the post-biopsy setting, especially when there is brisk pulsatile flow. A modified biopsy device could easily be manufactured to facilitate use of post-biopsy cauterization to minimize risk of bleeding and needle-tract seeding for high-risk patients. Such a simple maneuver could be performed following any biopsy where needle tract seeding or bleeding were thought to be a higher risk, as might occur when brisk backbleeding is seen from the outer needle, or with uncorrectable coagulopathies, anticoagulation, hypervascular tumors, vascular organ biopsies (i.e., spleen), or with the larger core samples often required for genomic or proteomic analysis. Such a biopsy might be a safer alternative to transjugular liver biopsy as well, although this remains speculative.

CT and Ultrasound Guided Stereotactic High Intensity Focused Ultrasound (HIFU)

To demonstrate the feasibility of CT and B‐mode Ultrasound (US) targeted HIFU, a prototype coaxial focused ultrasound transducer was registered and integrated to a CT scanner. CT and diagnostic ultrasound were used for HIFU targeting and monitoring, with the goals of both thermal ablation and non‐thermal enhanced drug delivery. A 1 megahertz coaxial ultrasound transducer was custom fabricated and attached to a passive position‐sensing arm and an active six degree‐of‐freedom robotic arm via a CT stereotactic frame. The outer therapeutic transducer with a 10 cm fixed focal zone was coaxially mounted to an inner diagnostic US transducer (2–4 megahertz, Philips Medical Systems). This coaxial US transducer was connected to a modified commercial focused ultrasound generator (Focus Surgery, Indianapolis, IN) with a maximum total acoustic power of 100 watts. This pre‐clinical paradigm was tested for ability to heat tissue in phantoms with monitoring and navigation from CT and live US. The feasibility of navigatio...

Subdermal Fluid for Skin Protection during Superficial Palliative Thermal Ablation

Editor: Radiofrequency (RF) ablation is increasingly being used to treat small tumors of the liver, breast, kidney, adrenal, and bone in addition to tumor debulking. RF ablation has been successful in the treatment of painful metastatic bone disease and has more recently been described for palliation of soft tissue cancer pain (1-3). Although a rare complication, skin burns from RF ablation have been reported during the tract-ablation portion of the procedure, along the edge of grounding pads, and from the insulating coating surrounding the needle being peeled off (4-6). A 23-year-old man with sarcoma presented for RF ablation for pain palliation of three rapidly enlarging soft tissue masses in the right subscapula, right chest wall, and left flank. The lesions were hypoechoic on ultrasound, and the needle had free motion within the lesion suggesting a cystic component or necrosis which can make the heating process during ablation difficult and longer (7). Due to the extremely superficial location of the lesions just under the skin and the potentially longer ablation time,the risk of skin burn was considered significant. As a result, 20 mL of 1% lidocaine was used as an anesthetic and more important, to insulate the skin and move the masses away from the skin by injecting in a subdermal location. The 3.8 cm × 3.5 cm right subscapular mass was ablated first. Before ablation, the distance between the skin surface and the superior margin of the tumor was 0.52 cm (Fig 1). After injection of 20 mL of 1% lidocaine, this distance increased to 1.14 cm (Figs ​(Figs22-​-3).3). The ablation was then performed without complication or evidence of skin burn. The same technique was also applied to the other two lesions on the chest wall and flank. We commonly use a similar technique to prevent diaphragmatic injury for those perihepatic tumors close to the diaphragm and adjacent organs (8). Figure (1) Soft tissue sarcoma mass 0.52 cm beneath the skin surface. Figure (2) Needle (arrow) during subdermal injection of 20 mL of 1% lidocaine. Figure (3) Increased distance between skin surface and tumor after injection of lidocaine. While we cannot recommend a minimum distance from the tumor to the skin that would prevent burn injury, in our own experience fluid protection is warranted when either two organs (ie, bowel and liver) or tumor and skin are less than 1.0 cm from each other. This simple maneuver may decrease the risk of ablating tumors that are very close to the skin surface and have the potential to result in significant burn injury during the heating process. The recommended minimum distance between skin and a vein being laser ablated is 10 mm (9), which supports the 10 mm threshold, but it may be an arbitrary number. However, further prospective study to determine the minimum distance to prevent skin burns and to confirm the safety of this approach is required.