Comparing the cytotoxicity of taurolidine, mitomycin C, and oxaliplatin on the proliferation of in vitro colon carcinoma cells following pressurized intra-peritoneal aerosol chemotherapy (PIPAC)

Performance of different nebulizers in clinical use for Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC)

OBJECTIVE

Technical ex-vivo comparison of commercial nebulizer nozzles used for Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC).

METHODS

The performance of four different commercial nebulizer nozzles (Nebulizer; HurriChemTM; MCR-4 TOPOL®; QuattroJet) was analysed concerning: i) technical design and principle of operation, ii) operational pressure as function of the liquid flow rate, iii) droplet size distribution via laser diffraction spectrometry, iv) spray cone angle, spray cone form as well as horizontal drug deposition by image-metric analyses and v) chemical resistance via exposing to a cytostatic solution and chemical composition by means of spark optical emission spectral analysis.

RESULTS

The Nebulizer shows quasi an identical technical design and thus also a similar performance (e.g., mass median droplet size of 29 μm) as the original PIPAC nozzles (MIP/ CapnoPen). All other nozzles show more or less a performance deviation to the original PIPAC nozzles. The HurriChemTM has a similar design and principle of operation as the Nebulizer, but provides a finer aerosol (22 μm). The principle of operation of MCR-4 TOPOL® and QuattroJet differ significantly from that of the original PIPAC nozzle technology. The MCR-4 TOPOL® offers a hollow spray cone with significantly larger droplets (50 μm) than the original PIPAC nozzles. The QuattroJet generates an aerosol (22 μm) similar to that of the HurriChemTM but with improved spatial drug distribution.

CONCLUSION

The availability of new PIPAC nozzles is encouraging but can also have a negative impact if their performance and efficacy is unknown. It is recommended that PIPAC nozzles that deviate from the current standard should be subject to bioequivalence testing and implementation in accordance with the IDEAL-D framework prior to routine clinical use.

PIPAC for Gastrointestinal Malignancies

The peritoneum is a common site of metastases for gastrointestinal tumors that predicts a poor outcome. In addition to decreased survival, peritoneal metastases (PMs) can significantly impact quality of life from the resulting ascites and bowel obstructions. The peritoneum has been a target for regional therapies due to the unique properties of the blood-peritoneum barrier. Cytoreductive surgery (CRS) and heated intraperitoneal chemotherapy (HIPEC) have become accepted treatments for limited-volume peritoneal disease in appendiceal, ovarian, and colorectal malignancies, but there are limitations. Pressurized intraperitoneal aerosolized chemotherapy (PIPAC) improves drug distribution and tissue penetration, allowing for a minimally invasive application for patients who are not CRS/HIPEC candidates based on high disease burden. PIPAC is an emerging treatment that may convert the patient to resectable disease, and may increase survival without major morbidity, as indicated by many small studies. In this review, we discuss the rationale and benefits of PIPAC, as well as sentinel papers describing its application for gastric, colorectal, appendiceal, and pancreatobiliary PMs. While no PIPAC device has yet met FDA approval, we discuss next steps needed to incorporate PIPAC into neoadjuvant/adjuvant treatment paradigms, as well as palliative settings. Data on active clinical trials using PIPAC are provided.

Triple-Therapy of Peritoneal Metastasis-Partial-Dehydration under Hyperthermic Condition Combined with Chemotherapy: The First Preliminary In-Vitro Results

A newly introduced combination of intraperitoneal dehydration and hyperthermia has recently been shown to be feasible and cytotoxic for colon cancer cells in vivo. For the first time, our study now aims to evaluate dehydration under hyperthermic conditions combined with chemotherapy for potential use in the clinical setting. In this study, in vitro colon cancer cells (HT-29) were subjected to single or several cycles of partial dehydration under hyperthermic conditions (45 °C), followed by chemotherapy (triple exposure) with oxaliplatin or doxorubicin in various configurations. The viability, cytotoxicity, and proliferation of cells after the proposed protocols were assessed. Intracellular doxorubicin uptake was measured via flow cytometry. After one cycle of triple exposure, the viability of HT-29 cells was significantly reduced versus the untreated control (65.11 ± 5%, p < 0.0001) and versus only chemotherapy (61.2 ± 7%, p < 0.0001). An increased chemotherapeutic inflow into the cells after triple exposure was detected (53.4 ± 11%) when compared to cells treated with chemotherapy alone (34.23 ± 10%) (p < 0.001). Partial dehydration in a hyperthermic condition combined with chemotherapy increases the overall cytotoxicity of colon cancer cells significantly compared to chemotherapy alone. This could possibly be related to enhanced intracellular uptake of chemotherapeutic agents after partial dehydration. Further studies are required for the further evaluation of this new concept.

Multicenter dose-escalation Phase I trial of mitomycin C pressurized intraperitoneal aerosolized chemotherapy in combination with systemic chemotherapy for appendiceal and colorectal peritoneal metastases: rationale and design

Objectives

Peritoneal metastasis (PM) from appendiceal cancer or colorectal cancer (CRC) has significant morbidity and limited survival. Pressurized intraperitoneal aerosolized chemotherapy (PIPAC) is a minimally invasive approach to treat PM. We aim to conduct a dose-escalation trial of mitomycin C (MMC)-PIPAC combined with systemic chemotherapy (FOLFIRI) in patients with PM from appendiceal cancer or CRC.

Methods

This is a multicenter Phase I study of MMC-PIPAC (NCT04329494). Inclusion criteria include treatment with at least 4 months of first- or second-line systemic chemotherapy with ineligibility for cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC). Exclusion criteria are: progression on chemotherapy; extraperitoneal metastases; systemic chemotherapy intolerance; bowel obstruction; or poor performance status (ECOG>2). Escalating MMC-PIPAC doses (7-25 mg/m2) will be administered in combination with standard dose systemic FOLFIRI. Safety evaluation will be performed on 15 patients (dose escalation) and six expansion patients: 21 evaluable patients total.

Results

The primary endpoints are recommended MMC dose and safety of MMC-PIPAC with FOLFIRI. Secondary endpoints are assessment of response (by peritoneal regression grade score; Response Evaluation Criteria in Solid Tumors [RECIST 1.1], and peritoneal carcinomatosis index), progression free survival, overall survival, technical failure rate, surgical complications, conversion to curative-intent CRS-HIPEC, patient-reported outcomes, and functional status. Longitudinal blood and tissue specimens will be collected for translational correlatives including pharmacokinetics, circulating biomarkers, immune profiling, and single-cell transcriptomics.

Conclusions

This Phase I trial will establish the recommended dose of MMC-PIPAC in combination with FOLFIRI. Additionally, we expect to detect an early efficacy signal for further development of this therapeutic combination.

Evaluating the concept of gas‑based intraperitoneal hyperthermia beyond 43˚C in the treatment of peritoneal metastasis: A pilot study

While hyperthermic intraperitoneal applications have demonstrated high efficacy in treating peritoneal metastases (PM), these applications are limited to temperatures of 41-43˚C to prevent a harmful increase in core temperature. However, since gaseous substances display low specific heat capacities, gas-based hyperthermia could potentially increase surface temperatures without affecting the body's core temperature. To the best of our knowledge, the present study is the first to explore the in vivo feasibility of gas-based hyperthermia via spatial and time-based distribution. In the present study, a temperature-isolated, abdominal box model was created with fresh peritoneal tissue exposed to continuous high-volume airflow temperatures ranging between 47 and 69˚C. Heat conduction within the peritoneal tissues was measured using temperature microsensors. Temperature build-up at different time points during the procedure was calculated and the safest option to perform gas-based intraperitoneal hyperthermia beyond 43˚C was identified using an in vivo swine model. In subsequent experiments, viability and cytotoxicity of HT-29 colon cancer cells were measured following short-term hyperthermia. The present study demonstrated that the application of gas-based intraperitoneal hyperthermia with temperatures up to 50˚C is possible without increasing the core temperature to harmful levels. Gas-based intraperitoneal hyperthermia can induce a histological reaction on the peritoneal surface, and it can also result in decreased viability and increased cytotoxicity of HT-29 cells. The concept of extreme hyperthermia may be of great clinical importance as it could significantly increase local cytotoxicity in PM without increasing the body's core temperature. Further studies are required to investigate the benefits, as well as the restrictions, of this novel concept.

In-vivo thermodynamic exploration of gas-based intraperitoneal hyperthermia

Background

While hyperthermic intraperitoneal (i.p) applications are highly efficient in treating peritoneal metastases (PM), they are currently limited to temperatures of 41 – 43° Celsius (C). First data on gas-based i.p. hyperthermia is promising, as this novel method allows a significant temperature rise in superficial peritoneal layers without increasing core temperatures. Until now, key mechanisms of this novel tool, e.g. thermodynamic energy transfer, have not been investigated. This study aims to explore the volume of thermodynamic energy transfer during gas-based i.p. hyperthermia at 48-50°C and its peritoneal effects.

Methods

For this study, three swine were subjected to gas-based i.p. hyperthermia at varying temperatures (48°, 49° and 50°C) in a diagnostic laparoscopy setting with a high-flow air stream. Temperatures of the i.p. cavity, in- and outflow airstream at the trocar were measured and the thermodynamic energy transfer was calculated. Tissue samples were collected on postoperative day 7 for histopathologic analyses.

Results

According to our data, temperatures within the intraabdominal cavity and at the outflow site remain relatively stable at < 40°C. An increase in thermodynamic energy transfer is observed with increasing applied temperatures. Gas-based i.p. hyperthermia induced capillary coagulation and white blood cell infiltration within peritoneal layers.

Conclusions

Gas-based i.p. hyperthermia is an innovative approach which enables the i.p. delivery of specific amounts of thermodynamic energy. Following this procedure, our data indicate remarkable histologic changes on the superficial peritoneal layer most likely attributable to the applied thermodynamic energy. Further studies are required to investigate how these findings can be applied in PM management.

The Onset of In-Vivo Dehydration in Gas -Based Intraperitoneal Hyperthermia and Its Cytotoxic Effects on Colon Cancer Cells

Background

Peritoneal metastasis (PM) is an ongoing challenge in surgical oncology. Current therapeutic options, including intravenous and intraperitoneal (i.p.) chemotherapies display limited clinical efficacy, resulting in an overall poor prognosis in affected patients. Combined hyperthermia and dehydration induced by a high-flow, gas-based i.p. hyperthermic procedure could be a novel approach in PM treatment. Our study is the first to evaluate the therapeutic potential of i.p. dehydration, hyperthermia, as well as the combination of both mechanisms in an in-vivo setting.

Methods

For this study, three swine were subjected to diagnostic laparoscopy under a high-flow air stream at 48°, 49° and 50°Celsius (C). Hygrometry of the in- and outflow airstream was measured to calculate surface evaporation and i.p. dehydration. To analyze the effects of this concept, in vitro colon cancer cells (HT-29) were treated with hyperthermia and dehydration. Cytotoxicity and cell viability were measured at different time intervals. Additionally, structural changes of dehydrated cells were analyzed using scanning electron microscopy.

Results

According to our results, both dehydration and hyperthermia were cytotoxic to HT-29 cells. However, while dehydration reduced cell viability, hyperthermia did not. However, dehydration effects on cell viability were significantly increased when combined with hyperthermia (p<0.01).

Conclusions

Changes to the physiological milieu of the peritoneal cavity could significantly reduce PM. Therefore, limited dehydration of the abdominal cavity might be a feasible, additional tool in PM treatment. Further studies are required to investigate dehydration effects and their applicability in PM management.

Exploring the potential of taurolidine in inducing mobilization and detachment of colon cancer cells: a preliminary in-vitro study

Background

Recently, taurolidine has been intensively studied on a variety of in-vitro cancer cell-lines and first data exhibit encouraging antitumoral effects. While the clinical use of taurolidine is considered, some studies with in-vivo experiments contradict this beneficial effect and even indicate advanced cancer growth. The aim of this study is to further investigate this paradox in-vivo effect by taurolidine and closely analyze the interaction of cancer cells with the surrounding environment following taurolidine exposure.

Methods

HT-29 (ATCC® HTB-38™) cells were treated with taurolidine at different concentrations and oxaliplatin using an in-vitro model. Morphological changes with respect to increasing taurolidine dosage were visualized and monitored using electron microscopy. Cytotoxicity of the agents as well as extent of cellular detachment by mechanical stress was measured for each substance using a colorimetric MTS assay.

Results

Both taurolidine and oxaliplatin exhibit cell toxicity on colon cancer cells. Taurolidine reshapes colon cancer cells from round into spheric cells and further induces cluster formation. When exposed to mechanical stress, taurolidine significantly enhances detachment of adherent colon carcinoma cells compared to the control (p < 0.05) and the oxaliplatin group (p < 0.05). This effect is dose dependent.

Conclusions

Beside its cytotoxic effects, taurolidine could also change mechanical interactions of cancer cells with their environment. Local cancer cell conglomerates could be mechanically mobilized and may cause metastatic growth further downstream. The significance of changes in cellular morphology caused by taurolidine as well as its interaction with the microenvironment must be further addressed in clinical cancer therapies. Further clinical studies are needed to evaluate both the safety and efficacy of taurolidine for the treatment of peritoneal surface malignancies.

Exploring Insulin Production Following Alveolar Islet Transplantation (AIT)

Recent studies have demonstrated the feasibility of islet implantation into the alveoli. However, until today, there are no data on islet behavior and morphology at their transplant site. This study is the first to investigate islet distribution as well insulin production at the implant site. Using an ex vivo postmortem swine model, porcine pancreatic islets were isolated and aerosolized into the lung using an endoscopic spray-catheter. Lung tissue was explanted and bronchial airways were surgically isolated and connected to a perfusor. Correct implantation was confirmed via histology. The purpose of using this new lung perfusion model was to measure static as well as dynamic insulin excretions following glucose stimulation. Alveolar islet implantation was confirmed after aerosolization. Over 82% of islets were correctly implanted into the intra-alveolar space. The medium contact area to the alveolar surface was estimated at 60 +/− 3% of the total islet surface. The new constructed lung perfusion model was technically feasible. Following static glucose stimulation, insulin secretion was detected, and dynamic glucose stimulation revealed a biphasic insulin secretion capacity during perfusion. Our data indicate that islets secrete insulin following implantation into the alveoli and display an adapted response to dynamic changes in glucose. These preliminary results are encouraging and mark a first step toward endoscopically assisted islet implantation in the lung.

Pressurized intraperitoneal aerosol chemotherapy (PIPAC) for peritoneal malignancy: initial experience of the first program in the Baltic countries

BACKGROUND

Peritoneal malignancies include primary and metastatic cancer of the peritoneal cavity. The most common origin for peritoneal metastasis is ovarian, gastric, and colorectal cancers. Irrespective of the origin, peritoneal metastases represent the advanced disease and are associated with poor long-term outcomes. The minimally invasive approach of pressurized intraperitoneal aerosol chemotherapy (PIPAC) allows repeated applications and objective assessment of tumor response by comparing histological samples. This study aimed to investigate the initial experience with PIPAC in the Baltic region.

METHODS

All patients who underwent PIPAC at Vilnius University Hospital Santaros Klinikos between 2015 and 2020 were included in this retrospective study. The primary outcome of the study was overall survival (OS) in patients with peritoneal carcinomatosis treated by PIPAC. The secondary outcomes included postoperative morbidity; peritoneal carcinomatosis index (PCI) and ascites reduction after treatment by PIPAC.

RESULTS

In total, 15 patients underwent 34 PIPAC procedures. PIPAC-related intraoperative and postoperative morbidity occurred in 3 (8.8%) of 34 procedures. Following PIPAC, the median PCI decreased from 8 (4; 15) to 5 (1; 16) in GC patients, although, the difference failed for significance, p = 0.581. In OC patients, PCI after PIPAC remained stable. Median overall survival after PIPAC procedure was 25 (95% CI 5-44) months. Ovarian cancer patients (22; 95% CI 12-44 months) had significantly higher OS, compared to gastric cancer patients (8; 95% CI 4-16 months), p = 0.018.

CONCLUSIONS

PIPAC is safe and feasible for patients with gastric and ovarian cancers peritoneal metastases.

Islet Transplantation in the Lung via Endoscopic Aerosolization: Investigation of Feasibility, Islet Cluster Cell Vitality, and Structural Integrity

Aerosolized drug delivery has recently attracted much attention as a possible new tool for the delivery of complex nanoparticles. This study aims to investigate whether catheter-based aerosolization of islets via endobronchial systems is a feasible option in islet transplantation. Besides investigating the feasibility of islet aerosolization, we also examined cluster cell vitality and structural integrity of the islets following aerosolization. Using an ex vivo postmortem swine model, porcine pancreatic islets were isolated and aerosolized with an endoscopic spray catheter. Following aerosolization, islet cell vitality and function were assessed via Calcein AM and propidium iodide as well as insulin production after glucose exposure. In the final step, the overall feasibility of the procedure and structural integrity of cells were analyzed and evaluated with respect to clinical applicability. No significant difference was detected in the viability of control islets (90.67 ± 2.19) vs aerosolized islets (90.68 ± 1.20). Similarly, there was no significant difference in control islets (1.62 ± 0.086) vs aerosolized islets (1.42 ± 0.11) regarding insulin release after stimulation. Indocyanine green marked islets were transplanted into the lung without major difficulty. Histological analysis confirmed retained structural integrity and predominant location in the alveolar cavity. Our ex vivo data suggest that catheter-based aerosolized islet cell delivery is a promising tool for the application of cell clusters. According to our data, islet cell clusters delivery is feasible from a mechanical and physical perspective. Moreover, cell vitality and structural integrity remain largely unaffected following aerosolization. These preliminary results are encouraging and represent a first step toward endoscopically assisted islet cell implantation in the lung.

The emergence of pressurized intraperitoneal aerosol chemotherapy as a palliative treatment option for patients with diffuse peritoneal metastases: a narrative review

Pressurized intraperitoneal aerosol chemotherapy (PIPAC) is an emerging palliative treatment for patients with unresectable peritoneal metastases. Potential advantages of PIPAC over current treatment options are a homogeneous intraperitoneal distribution, low local and systemic toxicity, and enhanced tumour penetration. Given these possible benefits, PIPAC is increasingly implemented in many centres worldwide. Scientific research into PIPAC is currently available from in vitro/in vivo/in animal studies, retrospective cohorts in humans, and phase I and II studies in humans. There are no results from randomised trials comparing PIPAC with conventional treatment, such as palliative systemic therapy. This narrative review aimed to provide an overview of the currently available literature on PIPAC. In general, repetitive PIPAC was feasible and safe for patients and operating room personnel. Primary and secondary non-access rates varied from 0-17% and 0-15%, respectively. Iatrogenic bowel injury was observed in 0-3% of PIPAC procedures. CTCAE grade 1-2 complications were common, mostly consisting of abdominal pain, nausea, vomiting, and fatigue. CTCAE grade 3-4 complications were uncommon, occurring on 0-15% of PIPAC procedures. Post-operative mortality rates of 0-2% were reported. The risk of occupational exposure to cytotoxic drugs was very low when strict safety guidelines were followed. Clinical heterogeneity was high in most studies, since, in general, patients with unresectable peritoneal metastases from a variety of primary tumours were included. Also, patients received either PIPAC monotherapy or PIPAC combined with concomitant systemic therapy, and were able to receive PIPAC in any line of palliative treatment. Since the results were generally not stratified for these three important factors, this severely complicates the interpretation of results. Based on the current literature, PIPAC may be regarded as a promising palliative treatment option in patients with diffuse peritoneal metastases. Initial results show that it is feasible and safe. However, well designed and (ideally) randomized controlled trials are urgently needed to determine the additional value of PIPAC in this setting. Until then, PIPAC should preferably be performed in the setting of clinical trials.

Intraperitoneal chemotherapy of the peritoneal surface using high-intensity ultrasound (HIUS): investigation of technical feasibility, safety and possible limitations

Introduction: The penetration of chemotherapeutic drugs into peritoneal nodules remains at levels well below 1 mm, thus significantly limiting the antitumor effect of intraperitoneal chemotherapy (IPC). Recently, high-Intensity ultrasound (HIUS) has been discovered as a potential tool to significantly improve peritoneal diffusion rates. Despite promising preliminary data, basic aspects regarding its technical feasibility, safety and possible limitations remain unclear. This study aims to enhance our current understanding of HIUS and test its applicability using an ex-vivo swine model. Methods: Three postmortem swine were subject to laparotomy and consecutive lavage with 0.9%NaCl saline and HIUS application. For this purpose, a large HIUS radiating pen was introduced into the abdominal cavity and HIUS was applied on two of the four abdominal quadrants for 300 seconds each at an output power of 70 W, 50 % amplitude and 20 kHz frequency. Following the procedure, small intestinal tissue samples were retrieved for further analyses. Results: Peritoneal and subperitoneal layers showed structural changes only visible on a microscopic level. The peritoneal layer was transformed into a mesh-like structure while the subperitoneal layer (depth of 142 +/- 28 µm) exhibited microcavities and vascular detachment from surrounding tissues. No bowel rupture or vascular perforations were observed. Conclusions: Our data indicate that HIUS is a technically feasible and safe add-on procedure for intraperitoneal chemotherapy (IPC) with measurable microscopic changes on the peritoneal surface. Pretreatment of the abdominal cavity with HIUS could significantly improve IPC efficacy. Further studies are required to optimize and evaluate this novel approach.

The concept of foam as a drug carrier for intraperitoneal chemotherapy, feasibility, cytotoxicity and characteristics

For decades, intraperitoneal chemotherapy (IPC) was delivered into the abdominal cavity as a liquid solution. This preliminary study aims to evaluate foam as a potential new drug carrier for IPC delivery. Foam-based intraperitoneal chemotherapy (FBIC) was produced with taurolidine, hydrogen peroxide, human serum, potassium iodide and doxorubicin/ oxaliplatin for both ex vivo and in vitro experiments. Analysis of FBIC efficacy included evaluation of cytotoxicity, tissue penetration, foam stability, temperature changes and total foam volume per time evaluation. FBIC showed penetration rates of about 275 ± 87 µm and higher cytotoxicity compared to controls and to conventional liquid IPC (p < 0.005). The volume of the generated foam was approximately 50-times higher than the initial liquid solution and temporarily stable. Foam core temperature was measured and increased to 47 °C after 9 min. Foam ingredients (total protein content) were evenly distributed within different locations. Our preliminary results are quite encouraging and indicate that FBIC is a feasible approach. However, in order to discuss a possible superior effect over conventional liquid or aerosolized chemo applications, further studies are required to investigate pharmacologic, pharmacodynamic and physical properties of FBIC.

Evaluation of Cell-detaching Effect of EDTA in Combination with Oxaliplatin for a Possible Application in HIPEC After Cytoreductive Surgery: A Preliminary in-vitro Study

BACKGROUND

Ethylenediaminetetraacetic acid (EDTA), a commonly used compound in laboratory medicine, is known for its membrane-destabilization capacity and cell-detaching effect. This preliminary study aims to assess the potential of EDTA in removing residual tumor cell clusters. Using an in-vitro model, this effect is then compared to the cytotoxic effect of oxaliplatin which is routinely administered during HIPEC procedures. The overall cell toxicity and cell detaching effects of EDTA are compared to those of Oxaliplatin and the additive effect is quantified.

METHODS

HT-29 (ATCC® HTB-38™) cells were treated with A) EDTA only B) Oxaliplatin only and C) both agents using an in-vitro model. Cytotoxicity and cell detachment following EDTA application were measured via colorimetric MTS assay. Additionally, detached cell groups were visualized using light microscopy and further analyzed by means of electron microscopy.

RESULTS

When solely applied, EDTA does not exhibit any cell toxicity nor does it add any toxicity to oxaliplatin. However, EDTA enhances the detachment of adherent colon carcinoma cells by removing up to 65% (p<0.05) of the total initial cell amount. In comparison, the sole application of highly concentrated oxaliplatin induced cell mortality by up to 66% (p<0.05). While detached cells showed no mortality after EDTA treatment, cell clusters exhibited a decreased amount of extracellular and adhesive matrix in-between cells. When combined, Oxaliplatin and EDTA display a significant additive effect with only 30% (mean p <0.01) of residual vitality detected in the initial well. EDTA and Oxaliplatin remove up to 81% (p <0.01) of adhesive HT-29 cells from the surface either by cytotoxic effects or cell detachment.

CONCLUSION

Our data support EDTA's potential to remove microscopical tumor cell clusters from the peritoneum and possibly act as a supplementary agent in HIPEC procedures with chemotherapy. While adding EDTA to HIPEC procedures may significantly decrease the risk of PM recurrence, further in-vivo and clinical trials are required to evaluate this effect.

The structural effect of high intensity ultrasound on peritoneal tissue: a potential vehicle for targeting peritoneal metastases

BACKGROUND

High-intensity ultrasound (HIUS) has been increasingly investigated as a possible tool in the treatment of multiple tumor entities. However, there is only little knowledge on the effect of HIUS on the peritoneum. This preliminary study aims to investigate HIUS' potential for altering the peritoneal surface and potentially improving current treatments for peritoneal metastases. For this purpose, HIUS' qualitative and quantitative structural effects on the peritoneal tissue were analyzed by means of light, fluorescence and electron microscopy.

METHODS

Proportional sections were cut from the fresh postmortem swine peritoneum. Peritoneal surfaces were covered with a 6 mm thick liquid film of 0.9% NaCl. HIUS was applied in all tissue samples for 0 (control), 30, 60, 120 and 300 s. Peritoneal tissues were analyzed using light-, fluorescence and electron microscopy to detect possible structural changes within the tissues.

RESULTS

Following HIUS, a superficial disruption of peritoneal tissue was visible in light microscopy, which amplified with increased time of HIUS' application. Fluorescence microscopy showed both peritoneal and subperitoneal disruption with tissue gaps. Electron microscopy revealed structural filamentation of the peritoneal surface.

CONCLUSION

Our data indicate that HIUS causes a wide range of effects on the peritoneal tissue, including the formation of small ruptures in both peritoneal and subperitoneal tissues. However, according to our findings, these disruptions are limited to a microscopical level. Further studies are required to evaluate whether HIUS application can benefit current therapeutic regimens on peritoneal metastases and possibly enhance the efficacy of intraperitoneal chemotherapy.

Intrathoracic aerosol chemotherapy via spray-catheter

Pressurized intrathoracic aerosol chemotherapy (PITAC) has been introduced to the clinical setting as a novel treatment option for pleural metastasis (PM). For decades the therapeutic application of aerosols was limited to intrabronchial delivery. However, present studies suggest performing PITAC on patients with PM and malignant pleural effusion. Using an established ex vivo swine model, the present study aimed to introduce a facilitated intrathoracic chemoaerosol application via spray-catheter. Using an ex-vivo model of 3 postmortem swine, the feasibility of intrathoracic aerosol chemotherapy (ITC) with doxorubicin using a spray-catheter was evaluated in a normal pressure environment. Following thoracotomy, the spray-catheter was inserted via trocar. Tissue samples were retrieved and further analyzed by fluorescence microscopy to detect doxorubicin contact. Our data demonstrated that the application of ITC was technically feasible and did not exhibit any significant obstacles. By making a minimally invasive thoracotomy incision it was possible to create an adequate pneumothorax without the need of a double-lumen tube or intubation. ITC did not require the creation of a pressurized environment. Tissue samples revealed doxorubicin contact within the pleura. In conclusion, ITC is a fast and feasible procedure that could possibly be administered via bedside application, therefore eliminating the need of an operating room and surgical staff. However, further studies are required to evaluate the safety of patients and physicians regarding this novel applicational modality. Nevertheless, the present study demonstrated that ITC may potentially be applied at bedside, an option that is particularly important for patients who do not qualify for PITAC procedures.

Creating nanocrystallized chemotherapy: the differences in pressurized aerosol chemotherapy (PAC) via intracavitary (IAG) and extracavitary aerosol generation (EAG) regarding particle generation, morphology and structure

Background: Nanocrystallization is a promising field for the development of new drugs. This study aims to present the use of nanocrystallization via intraperitoneal nanoaerosol therapy (INAT) for the treatment of peritoneal metastases.

Methods: A continuous aerosol generation device was used to aerosolize a highly concentrated doxorubicin solution within a dry CO₂ environment. The produced nanoaerosol was directed into an ex vivo abdominal model and collision of aerosol particles with placed samples was subject to further analysis via scanning-electron microscopy (SEM). SEM detected structural changes of particles caused by migration to different locations.

Results: It was possible to visualize the contact of doxorubicin aerosol particles with the surface. Larger particles as well as particles closer to the aerosol generation chamber collided with the glass sample creating liquid drops, while smaller particles with more distance to the aerosol chamber collided as highly concentrated nanocrystals. The amount of nanocrystal particles outweighed the amount of fluid aerosol particles by far.

Conclusions: Under optimal conditions, the formation of nanocrystals via aerosol creation device is possible. While a wide range of possible applications of nanocrystals is conceivable, surface coating with drug particles is especially interesting as it may serve as an alternative to conventional liquid intraperitoneal chemotherapy. Further studies are required to investigate nanocrystallization of chemotherapeutic solutions as well as its physical and pharmacological properties and side effects.

Overcoming Drug Resistance by Taking Advantage of Physical Principles: Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC)

Theoretical considerations as well as comprehensive preclinical and clinical data suggest that optimizing physical parameters of intraperitoneal drug delivery might help to circumvent initial or acquired resistance of peritoneal metastasis (PM) to chemotherapy. Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC) is a novel minimally invasive drug delivery system systematically addressing the current limitations of intraperitoneal chemotherapy. The rationale behind PIPAC is: (1) optimizing homogeneity of drug distribution by applying an aerosol rather than a liquid solution; (2) applying increased intraperitoneal hydrostatic pressure to counteract elevated intratumoral interstitial fluid pressure; (3) limiting blood outflow during drug application; (4) steering environmental parameters (temperature, pH, electrostatic charge etc.) in the peritoneal cavity for best tissue target effect. In addition, PIPAC allows repeated application and objective assessment of tumor response by comparing biopsies between chemotherapy cycles. Although incompletely understood, the reasons that allow PIPAC to overcome established chemoresistance are probably linked to local dose intensification. All pharmacological data published so far show a superior therapeutic ratio (tissue concentration/dose applied) of PIPAC vs. systemic administration, of PIPAC vs. intraperitoneal liquid chemotherapy, of PIPAC vs. Hyperthermic Intraperitoneal Chemotherapy (HIPEC) or PIPAC vs. laparoscopic HIPEC. In the initial introduction phase, PIPAC has been used in patients who were quite ill and had already failed multiple treatment regimes, but it may not be limited to that group of patients in the future. Rapid diffusion of PIPAC in clinical practice worldwide supports its potential to become a game changer in the treatment of chemoresistant isolated PM of various origins.

Increased Tissue Penetration of Doxorubicin in Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC) after High-Intensity Ultrasound (HIUS)

BACKGROUND

High-intensity ultrasound (HIUS) has been studied for the past two decades as a new therapeutic option for solid tumor direct treatment and a method for better chemotherapy delivery and perfusion. This treatment approach has not been tested to our knowledge in peritoneal metastatic therapy, where limited tissue penetration of intraperitoneal chemotherapy has been a main problem. Both liquid instillations and pressurized aerosols are affected by this limitation. This study was performed to evaluate whether HIUS improves chemotherapy penetration rates.

METHODS

High-intensity ultrasound (HIUS) was applied for 0, 5, 30, 60, 120, and 300 seconds on the peritoneal tissue samples from fresh postmortem swine. Samples were then treated with doxorubicin via pressurized intraperitoneal aerosol chemotherapy (PIPAC) under 12 mmHg and 37°C temperature. Tissue penetration of doxorubicin was measured using fluorescence microscopy on frozen thin sections.

RESULTS

Macroscopic structural changes, identified by swelling of the superficial layer of the peritoneal surface, were observed after 120 seconds of HIUS. Maximum doxorubicin penetration was significantly higher in peritoneum treated with HIUS for 300 seconds, with a depth of 962.88 ± 161.4 μm (p < 0.05). Samples without HIUS had a penetration depth of 252.25 ± 60.41. Tissue penetration was significantly increased with longer HIUS duration, with up to 3.8-fold increased penetration after 300 sec of HIUS treatment.

CONCLUSION

Our data indicate that HIUS may be used as a method to prepare the peritoneal tissue for intraperitoneal chemotherapy. Higher tissue penetration rates can be achieved without increasing chemotherapy concentrations and preventing structural damage to tissue using short time intervals. More studies need to be performed to analyze the effect of HIUS in combination with intraperitoneal chemotherapy.

Release of doxorubicin from its liposomal coating via high intensity ultrasound

The present ex vivo study was performed to analyze the impact of high intensity ultrasound (HIUS) on penetration depth and particle stability of liposomal doxorubicin (LD) on the peritoneal surface. Fresh post mortem swine peritoneum was cut into proportional sections and subjected to a previously established ex vivo model of pressurized intraperitoneal aerosol chemotherapy (PIPAC). Samples were treated with 50 ml NaCl (0.9%) containing 3 mg LD via PIPAC or lavage. In both groups, half of the samples received additional HIUS treatment. Samples treated via PIPAC were covered with a 30-mm-thick abdominal muscle wall tissue, fatty tissue and skin, followed by transcutaneous HIUS. Samples administered with LD via lavage received close-range contact HIUS. Doxorubicin tissue penetration was measured using fluorescence microscopy on frozen sections. Liposomal integrity on peritoneal surfaces was measured via electron microscopy (EM). Mean penetration rates of doxorubicin were significantly higher with HIUS in combination with PIPAC or lavage compared with PIPAC alone (P<0.001) or lavage alone (P<0.00001). LD was not detected on the peritoneal surface via EM analysis in either group following HIUS. The present data suggested that HIUS may be a feasible application that can facilitate the release of doxorubicin from its liposomal envelope. HIUS was effective in both close-range, in contact with the samples, and through the abdominal wall. The present approach may be used in the future for both endoscopic and open lavage of the peritoneal cavity with LD in intraperitoneal chemotherapeutic applications such as hyperthermic intraperitoneal chemotherapy or PIPAC.

A real-time ex vivo model (eIBUB) for optimizing intraperitoneal drug delivery as an alternative to living animal models

BACKGROUND

Optimization of intraperitoneal drug delivery systems requires functional models. We proposed the Inverted Bovine Urinary Bladder Model (IBUB), but IBUB does not allow repeated measurements over time and there is a significant biological variability between organs.

METHODS

A further development of IBUB is presented, based on the physical principle of communicating vessels. Fresh bovine bladders were inverted so that the peritoneum lines up the inner surface. The IBUB and a second vessel were then interconnected under the same CO2 pressure and placed on two scales. The therapeutic solution (Doxorubicin 2.7 mg and Cisplatin 13.5 mg) was delivered via an aerosolizer. All experiments were in triplicate and blinded to the origin of samples, measurements in a GLP-certified laboratory.

RESULTS

The enhanced IBUB (eIBUB) model allows measurements of tissue drug concentration, depth of tissue penetration and spatial distribution. The homogeneous morphology of the peritoneum enables standardized, multiple tissue sampling. eIBUB minimizes biological variability between different bladders and eliminates the bias caused by the liquid collecting at the bottom of the model. Concentration of doxorubicin in the eIBUB (mean ± STDV: 18.5 ± 22.6 ng/mg) were comparable to clinical peritoneal biopsies (19.2 ± 38.6 ng/mg), as was depth of drug penetration (eIBUB: mean (min-max) 433 (381-486) µm, clinical ~ 500 µm).

CONCLUSIONS

The eIBUB model is a simple and powerful ex vivo model for optimizing intraperitoneal drug delivery and represents an attractive alternative to animal models. Results obtained are similar to those obtained in the human patient.