Comparison of Tissue and Blood Concentrations of Oxaliplatin Administrated by Different Modalities of Intraperitoneal Chemotherapy.

BACKGROUND: Pressurized intraperitoneal aerosol chemotherapy (PIPAC) is a new technology for delivering intraperitoneal chemotherapy. It is generally assumed that with PIPAC, the ratio of peritoneal to systemic drug concentration is superior to liquid hyperthermic intraperitoneal chemotherapy (HIPEC). To date, no direct comparative data are available supporting such an assumption. MATERIALS AND METHODS: Twelve 65-day-old pigs were randomly separated into three groups of four pigs each, all of which received intraperitoneal chemotherapy using the following administration methods: PIPAC with oxaliplatin 92 mg in 150 ml dextrose 5% (Group 1); PIPAC with electrostatic aerosol precipitation (ePIPAC; Group 2); or laparoscopic HIPEC (L-HIPEC) with oxaliplatin 400 mg in 4 L dextrose 5% at 42 °C (Group 3). Serial blood and peritoneal tissue concentrations of oxaliplatin were determined by spectrometry. RESULTS: In all three groups, the maximum concentration of oxaliplatin in blood was detected 50-60 min after onset of the chemotherapy experiments, with no significant differences among the three groups (p = 0.7994). Blood oxaliplatin concentrations (0-30 min) were significantly higher in the L-HIPEC group compared with the ePIPAC group (p < 0.05). No difference was found for the overall systemic oxaliplatin absorption (area under the curve). Overall concentrations in the peritoneum were not different among the three groups (p = 0.4725), but were significantly higher in the visceral peritoneum in the PIPAC group (p = 0.0242). CONCLUSIONS: Blood and tissue concentrations were comparable between all groups; however, depending on the intraperitoneal area examined and the time points of drug delivery, the concentrations differed significantly between the three groups.

Cytotoxic effect of different treatment parameters in pressurized intraperitoneal aerosol chemotherapy (PIPAC) on the in vitro proliferation of human colonic cancer cells.

BACKGROUND: Pressurized intraperitoneal aerosol chemotherapy (PIPAC) has been recently reported as a new approach for intraperitoneal chemotherapy (IPC). By means of a patented micropump, the liquid chemotherapy is delivered into the peritoneal cavity as an aerosol which is supposed to achieve "gas-like" distribution. However, recent data report that the fraction of the submicron aerosol (gas-like) is less than 3 vol% of the total amount of aerosolized chemotherapy. Until today, possible modifications of treatment parameters during PIPAC with the aim of improving therapeutic outcomes have not been studied yet. This study aims to establish an in vitro PIPAC model to explore the cytotoxic effect of the submicron aerosol fraction and to investigate the impact of different application parameters on the cytotoxic effect of PIPAC on human colonic cancer cells. METHODS: An in vitro model using HCT8 colon adenocarcinoma wild-type cells (HCT8WT) and multi-chemotherapy refractory subline (HCT8RT) was established. Different experimental parameters such as pressure, drug dosage, time exposure, and system temperature were monitored in order to search for the conditions with a higher impact on cell toxicity. Cell proliferation was determined by means of colorimetric MTT assay 48 h following PIPAC exposures. RESULTS: Standard operational parameters applied for PIPAC therapy depicted a cytotoxic effect of the submicron aerosol fraction generated by the PIPAC micropump. We also observed that increasing pressure significantly enhanced tumor cell toxicity in both wild-type and chemotherapy-resistant cells. A maximum of cytotoxicity was observed at 15 mmHg. Pressure >15 mmHg did not show additional cytotoxic effect on cells. Increased oxaliplatin dosage resulted in progressively higher cell toxicity as expected. However, in resistant cells, a significant effect was only found at higher drug concentrations. Neither an extension of exposure time nor an increase in temperature of the aerosolized chemotherapy solution added an improvement in cytotoxicity. CONCLUSIONS: In this in vitro PIPAC model, the gas-like PIPAC aerosol fraction showed a cytotoxic effect which was enhanced by higher intra-abdominal pressure with a maximum at 15 mmHg. Similar findings were observed for drug dose escalation. A phase I dose escalation study is currently performed at our institution. However, increasing the intra-abdominal pressure might be a first and simple way to enhance the cytotoxic effect of PIPAC therapy which needs further clinical investigations.

Hyperthermic intracavitary nanoaerosol therapy (HINAT) as an improved approach for pressurised intraperitoneal aerosol chemotherapy (PIPAC): Technical description, experimental validation and first proof of concept.

Background: The delivery of aerosolised chemotherapeutic substances into pressurised capnoperitonea has been reported to be more effective than conventional liquid chemotherapy for the treatment of peritoneal carcinomatosis. However, recent reports reveal limitations of the currently available technology. Material and Methods: A novel approach for pressurised intraperitoneal aerosol chemotherapy (PIPAC), called hyperthermic intracavitary nanoaerosol therapy (HINAT), based on extracavitary generation of hyperthermic and unipolar charged aerosols, was developed. The aerosol size distribution, the spatial drug distribution and in-tissue depth penetration of HINAT were studied by laser diffraction spectrometry, differential electrical mobility analysis, time of flight spectrometry, scintigraphic peritoneography and fluorescence microscopy. All experiments were performed contemporaneous with conventional PIPAC for the purpose of comparison. Furthermore, a first proof of concept was simulated in anesthetised German Landrace pigs. Results: HINAT provides a nanometre-sized (63 nm) unipolar-charged hyperthermic (41 °C) drug aerosol for quasi uniform drug deposition over the whole peritoneum with significantly deeper drug penetration than that offered by conventional PIPAC.

Technical description of the microinjection pump (MIP®) and granulometric characterization of the aerosol applied for pressurized intraperitoneal aerosol chemotherapy (PIPAC).

BACKGROUND: Pressurized intraperitoneal aerosol chemotherapy (PIPAC) is gaining acceptance in clinical practice, but detailed information about the microinjection pump (MIP®), the generated aerosol and drug distribution is missing. ANALYTICAL METHODS: Ex vivo granulometric analyses by means of laser diffraction spectrometry were performed for MIP® aerosol characterization. Beside the standard operation conditions, the impact of the volumetric liquid flow rate on the aerosol characteristics was investigated with different liquids. Granulometric results as well as the local drug distribution were verified by ex vivo gravimetric analyses. On the basis of determined MIP® characteristics, the aerosol droplet size, which is necessary for a homogenous intra-abdominal drug distribution, was calculated. RESULTS: Granulometric analyses showed that the MIP® aerosol consists of a bimodal volume-weighted particle size distribution (PSD3) with a median droplet diameter of x 50,3 = 25 µm. Calculations reveal that the droplet size for a homogenous intra-abdominal drug distribution during PIPAC therapy should be below 1.2 µm. We show that >97.5 vol% of the aerosolized liquid is delivered as droplets with ≥3 µm in diameter, which are primarily deposited on the surface beneath the MIP® by gravitational settling and inertial impaction. These findings were confirmed by ex vivo gravimetric analyses, where more than 86.0 vol% of the aerosolized liquid was deposited within a circular area with a diameter of 15 cm. CONCLUSIONS: The granulometric aerosol properties, as well as the aerodynamic conditions achieved by standard MIP® operation, do not support the idea of widespread or homogenous drug distribution in the abdominal cavity.

Evaluating the Effect of Micropump© Position, Internal Pressure and Doxorubicin Dosage on Efficacy of Pressurized Intra-peritoneal Aerosol Chemotherapy (PIPAC) in an Ex Vivo Model.

BACKGROUND/AIM: Pressurized intraperitoneal aerosol chemotherapy (PIPAC) is a novel clinical approach to the treatment of peritoneal carcinomatosis. A well-established, not anatomic ex vivo PIPAC model was used to investigate the influence of changes in internal pressure, distance of the Micropump(©) (MIP) to the distributing surface and the drug concentration on the penetration depth of doxorubicin in the target tissue. MATERIALS AND METHODS: Doxorubicin was aerosolized in an ex vivo PIPAC model using a hermetic container system mimicking the abdominal cavity. Fresh post-mortem swine peritoneum was cut into proportional samples. Tissue specimens were spatially placed at 4 different spots within the box: P1, on the distributing surface of the box, directly opposite to MIP; P2, on the side wall of the box; P3, on the ceiling of the box; P4, on the distributing surface with a partial cover. Impact of changes in the following parameters were analyzed and compared with clinically established values (CEVs) at our center: pressure (CEV=12 mmHg), distance of the MIP from the distributing surface (CEV=8 cm) and doxorubicin concentration (CEV=3 mg/50 ml). In-tissue doxorubicin penetration depth was measured using fluorescence microscopy on frozen thin sections. RESULTS: Tissue positioning in the box had a significant impact on drug penetration after PIPAC with CEV. Under CEV conditions, the highest drug penetration depth was observed in the tissue placed on the distributing surface directly opposite to the MIP (P1: 351 µm, P2: 77 µm, P3: 66 µm, P4: 34 µm). A closer positioning of the MIP lead to a significantly higher mean depth penetration of doxorubicin in the P1 in contrast to other samples in which a reduced drug penetration was observed (1 cm vs. 8 cm distance from MIP to the distributing surface, P1 at 1 cm: 469 µm vs. P1 at 8 cm: 351 µm, p<0.0001; P2 at 1 cm: 25 µm vs. P2 at 8 cm: 77 µm, p<0.0001; P3 at 1 cm: 21 µm vs. P3 at 8 cm: 66 µm, p<0.001; P4 at 1 cm: 13 µm vs. P4 at 8 cm: 39 µm, p=0.021). Higher doxorubicin concentrations led to a highly significant increase of drug penetration in P1 (1 cm vs. 8 cm, p<0.0001), but only a little significant increase in other samples. An increase of internal pressure did not show a significant increase in penetration depth of doxorubicin. CONCLUSION: Our ex vivo data suggest that a higher pressure does not increase the penetration deepness of doxorubicin. Higher drug dosage and a closer positioning of the MIP toward the target lead to a higher penetration of doxorubicin within the samples. A more homogeneous penetration within all targets cannot be achieved by changing drug concentration, position of the nozzle or pressure increase.