Increasing the Dye Payload of Cetuximab-IRDye800CW Enables Photodynamic Therapy.

Cetuximab (Cet)-IRDye800CW, among other antibody-IRDye800CW conjugates, is a potentially effective tool for delineating tumor margins during fluorescence image-guided surgery (IGS). However, residual disease often leads to recurrence. Photodynamic therapy (PDT) following IGS is proposed as an approach to eliminate residual disease but suffers from a lack of molecular specificity for cancer cells. Antibody-targeted PDT offers a potential solution for this specificity problem. In this study, we show, for the first time, that Cet-IRDye800CW is capable of antibody-targeted PDT in vitro when the payload of dye molecules is increased from 2 (clinical version) to 11 per antibody. Cet-IRDye800CW (1:11) produces singlet oxygen, hydroxyl radicals, and peroxynitrite upon activation with 810 nm light. In vitro assays on FaDu head and neck cancer cells confirm that Cet-IRDye800CW (1:11) maintains cancer cell binding specificity and is capable of inducing up to ∼90% phototoxicity in FaDu cancer cells. The phototoxicity of Cet-IRDye800CW conjugates using 810 nm light follows a dye payload-dependent trend. Cet-IRDye800CW (1:11) is also found to be more phototoxic to FaDu cancer cells and less toxic in the dark than the approved chromophore indocyanine green, which can also act as a PDT agent. We propose that antibody-targeted PDT using high-payload Cet-IRDye800CW (1:11) could hold potential for eliminating residual disease postoperatively when using sustained illumination devices, such as fiber optic patches and implantable surgical bed balloon applicators. This approach could also potentially be applicable to a wide variety of resectable cancers that are amenable to IGS-PDT, using their respective approved full-length antibodies as a template for high-payload IRDye800CW conjugation.

KDM1A inhibition increases UVA toxicity and enhances photodynamic therapy efficacy.

BACKGROUND: Lysine-specific histone demethylase 1 (KDM1A/LSD1) regulates multiple cellular functions, including cellular proliferation, differentiation, and DNA repair. KDM1A is overexpressed in squamous cell carcinoma of the skin and inhibition of KDM1A can suppress cutaneous carcinogenesis. Despite the role of KDM1A in skin and DNA repair, the effect of KDM1A inhibition on cellular ultraviolet (UV) response has not been studied. METHODS: The ability of KDM1A inhibitor bizine to modify cell death after UVA and UVB exposure was tested in normal human keratinocytes and melanocytes, HaCaT, and FaDu cell lines. KDM1A was also downregulated using shRNA and inhibited by phenelzine in HaCaT and FaDu cells to confirm the role of KDM1A in UVA response. In addition, cellular reactive oxygen species (ROS) changes were assessed by a lipid-soluble fluorescent indicator of lipid oxidation, and ROS-related gene regulation using qPCR. During photodynamic therapy (PDT) studies HaCaT and FaDu cells were treated with aminolaevulinic acid (5-ALA) or HPPH (2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a) sodium and irradiated with 0-8 J/cm2 red LED light. RESULTS: KDM1A inhibition sensitized cells to UVA radiation-induced cell death but not to UVB. KDM1A inhibition increased ROS generation as detected by increased lipid peroxidation and the upregulation of ROS-responsive genes. The effectiveness of both ALA and HPPH PDT significantly improved in vitro in HaCaT and FaDu cells after KDM1A inhibition. CONCLUSION: KDM1A is a regulator of cellular UV response and KDM1A inhibition can improve PDT efficacy.

An Optical Surface Applicator for Intraoperative Photodynamic Therapy.

BACKGROUND AND OBJECTIVES: Intraoperative photodynamic therapy (IO-PDT) is typically administered by a handheld light source. This can result in uncontrolled distribution of light irradiance that impacts tissue and tumor response to photodynamic therapy. The objective of this work was to characterize a novel optical surface applicator (OSA) designed to administer controlled light irradiance in IO-PDT. STUDY DESIGN/MATERIALS AND METHODS: An OSA was constructed from a flexible silicone mesh applicator with multiple cylindrically diffusing optical fibers (CDF) placed into channels of the silicone. Light irradiance distribution, at 665 nm, was evaluated on the OSA surface and after passage through solid tissue-mimicking optical phantoms by measurements from a multi-channel dosimetry system. As a proof of concept, the light administration of the OSA was tested in a pilot study by conducting a feasibility and performance test with 665-nm laser light to activate 2-(1'-hexyloxyethyl) pyropheophorbide-a (HPPH) in the thoracic cavity of adult swine. RESULTS: At the OSA surface, the irradiance distribution was non-uniform, ranging from 128 to 346 mW/cm2 . However, in the tissue-mimicking phantoms, beam uniformity improved markedly, with irradiance ranges of 39-153, 33-87, and 12-28 mW/cm2 measured at phantom thicknesses of 3, 5, and 10 mm, respectively. The OSA safely delivered the prescribed light dose to the thoracic cavities of four swine. CONCLUSIONS: The OSA can provide predictable light irradiances for administering a well-defined and potentially effective therapeutic light in IO-PDT. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Irradiance controls photodynamic efficacy and tissue heating in experimental tumours: implication for interstitial PDT of locally advanced cancer.

BACKGROUND: Currently delivered light dose (J/cm2) is the principal parameter guiding interstitial photodynamic therapy (I-PDT) of refractory locally advanced cancer. The aim of this study was to investigate the impact of light dose rate (irradiance, mW/cm2) and associated heating on tumour response and cure. METHODS: Finite-element modeling was used to compute intratumoural irradiance and dose to guide Photofrin® I-PDT in locally advanced SCCVII in C3H mice and large VX2 neck tumours in New Zealand White rabbits. Light-induced tissue heating in mice was studied with real-time magnetic resonance thermometry. RESULTS: In the mouse model, cure rates of 70-90% were obtained with I-PDT using 8.4-245 mW/cm2 and ≥45 J/cm2 in 100% of the SCCVII tumour. Increasing irradiance was associated with increase in tissue heating. I-PDT with Photofrin® resulted in significantly (p < 0.05) higher cure rate compared to light delivery alone at same irradiance and light dose. Local control and/or cures of VX2 were obtained using I-PDT with 16.5-398 mW/cm2 and ≥45 J/cm2 in 100% of the tumour. CONCLUSION: In Photofrin®-mediated I-PDT, a selected range of irradiance prompts effective photoreaction with tissue heating in the treatment of locally advanced mouse tumour. These irradiances were translated for effective local control of large VX2 tumours.

A three-dimensional transient computational study of 532-nm laser thermal ablation in a geometrical model representing prostate tissue.

OBJECTIVE: Laser with 532-nm wavelength (GreenLightTM) is clinically approved to treat benign prostatic hyperplasia (BPH). However, low rate of tissue ablation and excessive thermal coagulation are shortcomings of this therapy. The goal of this study was to use a mathematical model to identify clinically viable laser settings that have the potential to improve treatment time and outcomes. METHODS: A three-dimensional transient computational model was developed, validated against analytical and experimental results, and utilized to investigate the response of tissues subjected to continuous-wave and pulsed lasers emitting 532-nm light (GreenLightTM laser). The impact of laser power (10-125 W), pulse duration (100 ns and 100 µs) and pulse frequency (10 and 100 Hz) on tissue ablation and coagulation rates and sizes was explored. RESULTS: Good agreement between the computational model and analytical and experimental results was found. Continuous-wave laser results in 13% less coagulation zone thickness and 10% higher ablation rate than the low frequency pulsed laser. With increasing laser power; ablation rate is expected to increase linearly, while coagulation zone thickness is expected to increase asymptotically. Pulse frequency influence on tissue ablation and coagulation is relevant at high power, but pulse duration is found to have minimal effect at all powers. CONCLUSIONS: Laser thermal tissue ablation employing continuous wave mode lasers outperforms that employing pulsed mode lasers. Laser power settings should be carefully selected to maximize the rate of tissue ablation and minimize tissue coagulation.

Surface markers for guiding cylindrical diffuser fiber insertion in interstitial photodynamic therapy of head and neck cancer.

BACKGROUND AND OBJECTIVES: Image-based treatment planning can be used to compute the delivered light dose during interstitial photodynamic therapy (I-PDT) of locally advanced head and neck squamous cell carcinoma (LA-HNSCC). The objectives of this work were to evaluate the use of surface fiducial markers and flexible adhesive grids in guiding interstitial placement of laser fibers, and to quantify the impact of discrepancies in fiber location on the expected light dose volume histograms (DVHs). METHODS: Seven gel-based phantoms were made to mimic geometries of LA-HNSCC. Clinical flexible grids and fiducial markers were used to guide the insertion of optically transparent catheters, which are used to place cylindrical diffuser fibers within the phantoms. A computed tomography (CT) was used to image the markers and phantoms before and after catheter insertion and to determine the difference between the planned and actual location of the catheters. A finite element method was utilized to compute the light DVHs. Statistical analysis was employed to evaluate the accuracy of fiber placement and to investigate the correlation between the location of the fibers and the calculated DVHs. RESULTS: There was a statistically significant difference (P = 0.018) between all seven phantoms in terms of the mean displacement. There was also statistically significant correlation between DVHs and depth of insertion (P = 0.0027), but not with the lateral displacement (P = 0.3043). The maximum difference between actual and planned DVH was related to the number of fibers (P = 0.0025) and the treatment time. CONCLUSIONS: Surface markers and a flexible grid can be used to assist in the administration of a prescribed DVH within 15% of the target dose provided that the treatment fibers are placed within 1.3 cm of the planned depth of insertion in anatomies mimicking LA-HNSCC. The results suggest that the number of cylindrical diffuser fibers and treatment time can impact the delivered DVHs. Lasers Surg. Med. 49:599-608, 2017. © 2017 Wiley Periodicals, Inc.

Quantum dot light emitting devices for photomedical applications.

While OLEDs have struggled to find a niche lighting application that can fully take advantage of their unique form factors as thin, flexible, lightweight and uniformly large-area luminaire, photomedical researchers have been in search of low-cost, effective illumination devices with such form factors that could facilitate widespread clinical applications of photodynamic therapy (PDT) or photobiomodulation (PBM). Although existing OLEDs with either fluorescent or phosphorescent emitters cannot achieve the required high power density at the right wavelength windows for photomedicine, the recently developed ultrabright and efficient deep red quantum dot light emitting devices (QLEDs) can nicely fit into this niche. Here, we report for the first time the in-vitro study to demonstrate that this QLED-based photomedical approach could increase cell metabolism over control systems for PBM and kill cancerous cells efficiently for PDT. The perspective of developing wavelength-specific, flexible QLEDs for two critical photomedical fields (wound repair and cancer treatment) will be presented with their potential impacts summarized. The work promises to generate flexible QLED-based light sources that could enable the widespread use and clinical acceptance of photomedical strategies including PDT and PBM.

A new finite element approach for near real-time simulation of light propagation in locally advanced head and neck tumors.

BACKGROUND AND OBJECTIVES: Several clinical studies suggest that interstitial photodynamic therapy (I-PDT) may benefit patients with locally advanced head and neck cancer (LAHNC). For I-PDT, the therapeutic light is delivered through optical fibers inserted into the target tumor. The complex anatomy of the head and neck requires careful planning of fiber insertions. Often the fibers' location and tumor optical properties may vary from the original plan therefore pretreatment planning needs near real-time updating to account for any changes. The purpose of this work was to develop a finite element analysis (FEA) approach for near real-time simulation of light propagation in LAHNC. METHODS: Our previously developed FEA for modeling light propagation in skin tissue was modified to simulate light propagation from interstitial optical fibers. The modified model was validated by comparing the calculations with measurements in a phantom mimicking tumor optical properties. We investigated the impact of mesh element size and growth rate on the computation time, and defined optimal settings for the FEA. We demonstrated how the optimized FEA can be used for simulating light propagation in two cases of LAHNC amenable to I-PDT, as proof-of-concept. RESULTS: The modified FEA was in agreement with the measurements (P = 0.0271). The optimal maximum mesh size and growth rate were 0.005-0.02 m and 2-2.5 m/m, respectively. Using these settings the computation time for simulating light propagation in LAHNC was reduced from 25.9 to 3.7 minutes in one case, and 10.1 to 4 minutes in another case. There were minor differences (1.62%, 1.13%) between the radiant exposures calculated with either mesh in both cases. CONCLUSIONS: Our FEA approach can be used to model light propagation from diffused optical fibers in complex heterogeneous geometries representing LAHNC. There is a range of maximum element size (MES) and maximum element growth rate (MEGR) that can be used to minimize the computation time of the FEA to 4 minutes.

Correlation of Bronchoscopy and CT in Characterizing Malignant Central Airway Obstruction.

BACKGROUND: Malignant Central Airway Obstruction (MCAO) presents a significant challenge in lung cancer management, with notable morbidity and mortality implications. While bronchoscopy is the established diagnostic standard for confirming MCAO and assessing obstruction subtype (intrinsic, extrinsic, mixed) and severity, Computed Tomography (CT) serves as an initial screening tool. However, the extent of agreement between CT and bronchoscopy findings for MCAO remains unclear. METHODS: To assess the correlation between bronchoscopy and CT, we conducted a retrospective review of 108 patients at Roswell Park Comprehensive Cancer Center, analyzing CT and bronchoscopy results to document MCAO presence, severity, and subtype. RESULTS: CT correctly identified MCAO in 99% of cases (107/108). Agreement regarding obstruction subtype (80.8%, Cohen's κ = 0.683, p < 0.001), and severity (65%, Quadratic κ = 0.657, p < 0.001) was moderate. CT tended to equally overestimate (7/19) and underestimate (7/19) the degree of obstruction. CT was also poor in identifying mucosal involvement in mixed MCAO. CONCLUSIONS: CT demonstrates reasonable agreement with bronchoscopy in detecting obstruction. Nevertheless, when CT indicates a positive finding for MCAO, it is advisable to conduct bronchoscopy. This is because CT lacks reliability in determining the severity of obstruction and identifying the mucosal component of mixed disease.

Epidemiology and Survival of Malignant Central Airway Obstruction in Lung Cancer Identified on Cross-Sectional Imaging.

BACKGROUND: The prevalence of malignant central airway obstruction at diagnosis and its 5-year incidence are largely unknown, as are basic epidemiological data pertaining to this serious condition. To address these data limitations, we retrospectively collected data from the cohort of patients diagnosed with lung cancer at our institution in 2015 and followed cohort patients 5 years forward, until 2020. METHODS: We reviewed index PET/CT or CT scans at the time of lung cancer diagnosis to identify the presence, subtype, and severity of malignant central airway obstruction as well as progression/development over the next 5 years. RESULTS: The prevalence of malignant central airway obstruction affecting the airway lumen by 25% or greater was 17%, and its 5-year incidence of development was 8.2%. Notable associations from the multivariate analysis included a younger age and a stepwise increase in obstruction with increasing stage of disease. Squamous cell carcinoma and small-cell lung cancer were the 2 histologic subtypes with the strongest association with obstruction. The presence of malignant central airway obstruction either at time of diagnosis or on follow-up imaging was associated with significantly shortened survival (multivariate Cox proportional HR for MCAO=1.702, P<0.001). CONCLUSION: This study provides the first systematic characterization of fundamental epidemiological data on malignant central airway obstructions at a tertiary cancer center in the United States. This data is important to inform research directions and funding efforts of this serious complication. It also serves as a baseline value against which to compare for future studies.

Hyperthermia-enhanced indocyanine green delivery for laser-induced thermal ablation of carcinomas.

PURPOSE: Intravenous administration of indocyanine green (ICG) dye can effectively convert near-infrared (NIR) laser light into heat and enhance thermal injury of blood vessels; however, there is no selective uptake of ICG by the tumour compared to the other tissues, which impacts the therapeutic ratio of this strategy unless uptake can be selectively increased in tumour tissue. Here we investigated the use of local hyperthermia prior to intravenous ICG administration to enhance ICG uptake in tumour tissue, thereby enhancing laser thermal ablation of solid tumours. METHODS: Murine SCK breast or SCCVII head and neck tumours were treated with a 755-nm laser light either alone or with prior intravenous administration of 4 mg/kg ICG and/or local tumour hyperthermia at 42.5 °C for 60 min. Retention of ICG was quantified using a NIR animal imaging system. Treatment effects were assessed by growth delay and histology. RESULTS: ICG accumulation in the heated tumours was 1.23-fold greater on average compared to non-heated tumours, in both models. In SCK tumours, animals receiving either laser irradiation alone or in conjunction with ICG had a 1.86- or 3.91-fold increase in tumour growth delay, respectively. The addition of local hyperthermia before ICG injection resulted in complete regression of SCK tumours. Uptake of ICG increased in SCCVII tumours; however, little change in tumour growth delay was observed. CONCLUSION: Using local hyperthermia may improve the delivery of ICG to the tumour and thereby increase the extent of laser thermal ablation of smaller superficial malignancies that can be effectively exposed to laser therapy.

Computational Optimization of Irradiance and Fluence for Interstitial Photodynamic Therapy Treatment of Patients with Malignant Central Airway Obstruction.

There are no effective treatments for patients with extrinsic malignant central airway obstruction (MCAO). In a recent clinical study, we demonstrated that interstitial photodynamic therapy (I-PDT) is a safe and potentially effective treatment for patients with extrinsic MCAO. In previous preclinical studies, we reported that a minimum light irradiance and fluence should be maintained within a significant volume of the target tumor to obtain an effective PDT response. In this paper, we present a computational approach to personalized treatment planning of light delivery in I-PDT that simultaneously optimizes the delivered irradiance and fluence using finite element method (FEM) solvers of either Comsol Multiphysics® or Dosie™ for light propagation. The FEM simulations were validated with light dosimetry measurements in a solid phantom with tissue-like optical properties. The agreement between the treatment plans generated by two FEMs was tested using typical imaging data from four patients with extrinsic MCAO treated with I-PDT. The concordance correlation coefficient (CCC) and its 95% confidence interval (95% CI) were used to test the agreement between the simulation results and measurements, and between the two FEMs treatment plans. Dosie with CCC = 0.994 (95% CI, 0.953-0.996) and Comsol with CCC = 0.999 (95% CI, 0.985-0.999) showed excellent agreement with light measurements in the phantom. The CCC analysis showed very good agreement between Comsol and Dosie treatment plans for irradiance (95% CI, CCC: 0.996-0.999) and fluence (95% CI, CCC: 0.916-0.987) in using patients' data. In previous preclinical work, we demonstrated that effective I-PDT is associated with a computed light dose of ≥45 J/cm2 when the irradiance is ≥8.6 mW/cm2 (i.e., the effective rate-based light dose). In this paper, we show how to use Comsol and Dosie packages to optimize rate-based light dose, and we present Dosie's newly developed domination sub-maps method to improve the planning of the delivery of the effective rate-based light dose. We conclude that image-based treatment planning using Comsol or Dosie FEM-solvers is a valid approach to guide the light dosimetry in I-PDT of patients with MCAO.

Indocyanine green enhanced near-infrared laser treatment of murine mammary carcinoma.

It is well accepted that near-infrared (NIR) lasers are appropriate to ablate benign lesions and induce irreversible thermal injury in deeply seated blood vessels. At this wavelength, the laser light penetrates deep (3-5 mm) into the skin. However, many researchers have reported noticeable pain, extending from mild to severe, during and immediately after NIR laser treatment. Intravenous administration of an exogenous chromophore [indocyanine green (ICG), dye] can effectively convert NIR laser light into heat. In this approach, the presence of ICG has shown to enhance thermal injury of blood vessels in the treatment of healthy tissues. However, the effectiveness of thermal injury on the regression of cutaneous carcinomas during ICG/NIR laser therapy has not been assessed. The purpose of our study was to evaluate the potential benefit of using ICG/NIR laser therapy to regress superficial carcinoma with thermal injury. Two groups of A/J mice with subcutaneous mammary adenocarcinoma tumors (7-9 mm) were irradiated with a 808-nm NIR laser preceded by tail vein injection of ICG dye or sterile saline. Histological evaluation of the subcutaneous tissue revealed minor thermal damage and necrosis in the laser/saline group and substantial damage (up to 100% necrosis) in the laser/ICG group. The laser/ICG-treated group showed a steady reduction in tumor volume compared to the laser/saline group: 48% by day 5 (p = 0.045) and 69-70% by days 8, 9 and 10 (p values 0.0005 or less). The vascular-targeted ICG-NIR laser therapy appears to have potential for treating superficial tumors.

Conductive thermal ablation of 4T1 murine breast carcinoma reduces severe hypoxia in surviving tumour.

PURPOSE: The purpose of this study was to quantify hypoxia changes in viable tumour volumes after thermal ablation of a murine breast carcinoma. METHODS: Murine breast 4T1 tumours were grown in the rear leg of BALB/c mice to an average diameter of 10-12 mm. Tumours were treated with conductive interstitial thermal therapy (CITT) at a peak temperature of 80-90°C for 10 min. The animals were euthanised 72 h later, and the tumours were removed for immunohistochemical staining with pimonidazole - a marker of partial pressure of oxygen. The levels of pimonidazole staining intensity were used to quantify changes in hypoxia gradients in terms of strong, medium and weak positive pixel fractions. RESULTS: The pimonidazole staining ratio of viable control tumour tissue to viable tissue in tumours that were ablated was 0.7 for weak staining, 2.7 for medium staining and 8.0 (p < 0.03) for strong pimonidazole staining. CONCLUSION: This shift of pimonidazole staining toward lower intensity pixels in the remaining tumour indicates that tumour ablation with CITT may increase radiosensitivity of the remaining tumour tissue and presents a rationale for combination therapy.

SonoKnife for ablation of neck tissue: in vivo verification of a computer layered medium model.

PURPOSE: This study aimed to determine which treatment parameters of the SonoKnife device can be used to safely and effectively perform non-invasive thermal ablation of subcutaneous tissue. METHODS: A three-dimensional computational layered medium model was constructed to simulate thermal ablation treatment of the SonoKnife device. The acoustic and thermal fields were calculated with the Fast Object-Oriented C++ Ultrasound-Simulator software and a finite difference code, respectively. Subcutaneous tissue was represented as layers of skin, fat and muscle. The simulations were conducted for ultrasound frequencies of 1 or 3.5 MHz. The thermal dose model was used to predict the size and location of the ablated regions. The computer simulations were verified by using the SonoKnife to perform subcutaneous ablations in the neck area of healthy pigs, in vivo. Triphenyltetrazolium chloride viability stain was used to differentiate viable tissue from ablated regions ex vivo. RESULTS: The simulations for the layered medium model suggest that operating the SonoKnife at frequency of 1 MHz is more effective and safer than 3.5 MHz providing skin cooling is applied prior to ablation. These predictions were in agreement with the results observed in the animal studies. The required sonication time for ablation increased from 50 to 300 s by using 1 MHz. CONCLUSION: Our modelling and animal studies suggest that 1 MHz with pretreatment skin cooling are the optimal settings to operate the SonoKnife to safely and effectively perform subcutaneous thermal ablation of porcine skin. More work is needed to optimise skin cooling and define the optimal sonication time.

Indocyanine green-augmented diode laser therapy of telangiectatic leg veins: a randomized controlled proof-of-concept trial.

BACKGROUND: Telangiectatic leg veins, which affect about 40-50% of adults, represent a frequent cosmetic rather than a medical problem. Besides sclerotherapy, various laser devices are common treatment options. However, complete clearance rates can only be achieved in a small number of patients. OBJECTIVE: In this proof-of-concept study, the safety and efficacy of indocyanine green (ICG)-augmented diode laser therapy (808 nm) was evaluated for the treatment of telangiectatic leg veins. METHODS: ICG (2 mg/kg body weight) was intravenously administered in 15 female patients (skin type II to III) with telangiectatic leg veins (measuring between 0.25 and 3 mm in diameter). Immediately after ICG injection, diode laser pulses with different radiant exposures (50-110 J/cm(2)) were applied as one single treatment. Safety and efficacy were assessed 1 and 3 months after treatment by a blinded investigator and the patient. Treatments with the pulsed dye laser (PDL) and the diode laser without ICG served as reference therapies. RESULTS: The safety of ICG application and diode laser treatment was excellent in all patients with no persisting side effects. Vessel clearance was dose-dependent. Diode laser treatment at radiant exposures between 100 and 110 J/cm(2) resulted in good vessel clearance, which even improved to excellent after the application of double pulses. Diode laser therapy without ICG and PDL treatment induced poor to moderate clearance of telangiectatic leg veins. CONCLUSION: ICG-augmented diode laser therapy has proved to be a safe and effective treatment option for telangiectatic leg veins.

In Vivo Models for Studying Interstitial Photodynamic Therapy of Locally Advanced Cancer.

Interstitial photodynamic therapy (I-PDT) is a promising therapy considered for patients with locally advanced cancer. In I-PDT, laser fibers are inserted into the tumor for effective illumination and activation of the photosensitizer in a large tumor. The intratumoral light irradiance and fluence are critical parameters that affect the response to I-PDT. In vivo animal models are required to conduct light dose studies, to define optimal irradiance and fluence for I-PDT. Here we describe two animal models with locally advanced tumors that can be used to evaluate the response to I-PDT. One model is the C3H mouse bearing large subcutaneous SCCVII carcinoma (400-600 mm3). Using this murine model, multiple light regimens with one or two optical fibers with cylindrical diffuser ends (cylindrical diffuser fiber, CDF) can be used to study tumor response to I-PDT. However, tissue heating may occur when 630 nm therapeutic light is delivered through CDF at an intensity ≥60 mW/cm and energy ≥100 J/cm. These thermal effects can impact tumor response while treating locally advanced mice tumors. Magnetic resonance imaging and thermometry can be used to study these thermal effects. A larger animal model, New Zealand White rabbit with VX2 carcinoma (~5000 mm3) implanted in either the sternomastoid (neck implantation model) or the biceps femoris muscle (thigh implantation model), can be used to study I-PDT with image-based pretreatment planning using computed tomography. In the VX2 model, the light delivery can include the use of multiple laser fibers to test light dosimetry and delivery that are relevant for clinical use of I-PDT.

Interstitial Photothermal Therapy Generates Durable Treatment Responses in Neuroblastoma.

Photothermal therapy (PTT) represents a promising modality for tumor control typically using infrared light-responsive nanoparticles illuminated by a wavelength-matched external laser. However, due to the constraints of light penetration, PTT is generally restricted to superficially accessible tumors. With the goal of extending the benefits of PTT to all tumor settings, interstitial PTT (I-PTT) is evaluated by the photothermal activation of intratumorally administered Prussian blue nanoparticles with a laser fiber positioned interstitially within the tumor. This interstitial fiber, which is fitted with a terminal diffuser, distributes light within the tumor microenvironment from the "inside-out" as compared to from the "outside-in" traditionally observed during superficially administered PTT (S-PTT). I-PTT improves the heating efficiency and heat distribution within a target treatment area compared to S-PTT. Additionally, I-PTT generates increased cytotoxicity and thermal damage at equivalent thermal doses, and elicits immunogenic cell death at lower thermal doses in targeted neuroblastoma tumor cells compared to S-PTT. In vivo, I-PTT induces significantly higher long-term tumor regression, lower rates of tumor recurrence, and improved long-term survival in multiple syngeneic murine models of neuroblastoma. This study highlights the significantly enhanced therapeutic benefit of I-PTT compared to traditional S-PTT as a promising treatment modality for solid tumors.

First-In-Human Computer-Optimized Endobronchial Ultrasound-Guided Interstitial Photodynamic Therapy for Patients With Extrabronchial or Endobronchial Obstructing Malignancies.

Objective: Patients with inoperable extrabronchial or endobronchial tumors who are not candidates for curative radiotherapy have dire prognoses with no effective long-term treatment options. To reveal that our computer-optimized interstitial photodynamic therapy (I-PDT) is safe and potentially effective in the treatment of patients with inoperable extra or endobronchial malignancies inducing central airway obstructions. Methods: High-spatial resolution computer simulations were used to personalize the light dose rate and dose for each tumor. Endobronchial ultrasound with a transbronchial needle was used to place the optical fibers within the tumor according to an individualized plan. The primary and secondary end points were safety and overall survival, respectively. An exploratory end point evaluated changes in immune markers. Results: Eight patients received I-PDT with planning, and five of these received additional external beam PDT. Two additional patients received external beam PDT. The treatment was declared safe. Three of 10 patients are alive at 26.3, 12, and 8.3 months, respectively, after I-PDT. The treatments were able to deliver a prescribed light dose rate and dose to 87% to 100% and 18% to 92% of the tumor volumes, respectively. A marked increase in the proportion of monocytic myeloid-derived suppressor cells expressing programmed death-ligand 1 was measured in four of seven patients. Conclusions: Image-guided light dosimetry for I-PDT with linear endobronchial ultrasound transbronchial needle is safe and potentially beneficial in increasing overall survival of patients. I-PDT has a positive effect on the immune response including an increase in the proportion of programmed death-ligand 1-expressing monocytic myeloid-derived suppressor cells.

An alternating focused ultrasound system for thermal therapy studies in small animals.

PURPOSE: To develop an alternating focused ultrasound system (AFUS) for preclinical studies of thermal and acoustic responses of tumors in small animal models. This work was motivated by the need of noninvasively creating relatively small spheroidal thermal lesions in small targets (e.g., a murine tumor) without damaging the surrounding tissues. METHODS: The AFUS consists of two lead zirconate titanate (PZT-4) spherically curved ultrasound transducers with focal zones crossing each other at a 90 degrees angle. The transducers were independently powered following a programed alternating firing scheme. Before the device design and construction, an acoustic and biothermal model was developed to simulate the ultrasound pressure field and the resulting temperature and thermal dose distributions. A shape factor, sphericity, to quantify the roundness of the lesions was calculated based on the 240 equivalent minutes at 43 degrees C thermal dose contours. A prototype of the AFUS was constructed with two identical transducers of an operating frequency of 2.25 MHz, 38 mm in diameter, and F-number equal to 1.33. To evaluate the performance of the AFUS experimentally, a series of heating in polyacrylamide phantoms, ex vivo porcine liver tissues, and in implanted mouse tumors fibrosarcoma (FSaII) in vivo was conducted. In these experimental cases, the sphericity was calculated and compared based on the visible lesion (a marked change in coloration). RESULTS: As shown in the simulations, the lesions induced in polyacrylamide phantoms, ex vivo porcine liver tissues, and in vivo mouse tumors, the sphericities of the lesions yielded by AFUS heating were approximately 50% higher than those of single focused ultrasound heating as long as moderate intensities were used and the duty cycle pulses were distributed equally among the transducers. CONCLUSIONS: The AFUS is a device capable of noninvasively creating spheroidal thermal lesions in small targets such as murine tumors.