MR-guided high intensity focused ultrasound mediated hyperthermia for targeted drug delivery to treat pancreatic cancer
Navid Farr1, Yak-Nam Wang2, Samantha D’Andrea3, Frank Starr2, Ari Partanen4, Kayla Gravelle3, Donghoon Lee5, and Joo Ha Hwang1,3

1Department of Bioengineering, University of Washington, Seattle, WA, United States, 2Applied Physics Laboratory, University of Washington, Seattle, WA, United States, 3Department of Medicine, University of Washington, Seattle, WA, United States, 4Philips Healthcare, Andover, MA, United States, 5Department of Radiology, University of Washington, Seattle, WA, United States

Synopsis

Pancreatic cancer has one of the lowest survival rates because current therapies are ineffective. Dense stromal tissue and poor vascular perfusion limits drug penetration and uptake into the tumor. Growing evidence suggests that hyperthermia in combination with temperature sensitive liposomal drug delivery can lead to increased organ perfusion and drug extravasation resulting in high local drug concentration. We performed MR-guided heating methods that enable accurate and precise spatial and temporal control of heating. Enhanced drug delivery was achieved to treat pancreatic tumors using Magnetic Resonance-guided High Intensity Focused Ultrasound (MR-HIFU) in conjunction with a heat triggered drug delivery system.

Target audience

Researchers working on new therapies and drug developments for pancreatic cancer and groups working on preclinical studies with interest in noninvasive monitoring technique will benefit from this work.

Purpose

Pancreatic cancer is the fourth leading cause of cancer mortality rates in the United States. Current treatment options are of limited benefit with a five-year survival rate following diagnosis of less than 5% (1). Dense stroma and poor vascular perfusion limits drug penetration and uptake into the tumor tissue. Growing evidence suggests that hyperthermia can decrease drug resistance by enhancing cellular uptake (2). MR-guided heating methods enable accurate and precise spatial and temporal control of heating, and when coupled with temperature sensitive liposomes (TSLs), could result in tightly targeted drug delivery (3,4). The goal of the study was to evaluate enhanced drug delivery to treat pancreatic tumor in a clinically relevant transgenic mouse model using Magnetic Resonance-guided High Intensity Focused Ultrasound (MR-HIFU) in conjunction with a heat triggered drug delivery system.

Methods

Two different mouse models of pancreatic ductal adenocarcinoma were analyzed for these studies: a transgenic mouse model (KPC) and an induced orthotopic model. An animal positioning system with an integrated 4-channel small animal Magnetic Resonance Imaging (MRI) coil (Philips Medical Systems, Helsinki, Finland) was used with the MR-HIFU system (Sonalleve®, Philips Healthcare) to hold, image and treat the mice assigned to the experimental group. The mild hyperthermia heating algorithm resulted in a tight target temperature range (41 ± 0.5°C, target = 40 - 41°C) which was homogeneous within the ROI (Figure 1). Approximately 20 s were required to achieve the target temperature (Figure 2). Defined tumor tissue was treated by targeted sonications (1.2 MHz frequency, 7W acoustic power) in 5-10 minute increments with a total time of 30 minutes after injection of free doxorubicin (Dox) or TSLs loaded with Dox (ThermoDox®, Celcion Corporation). Temperature elevation during sonications was monitored by a gradient echo based echo planar imaging (EPI) sequence with an EPI factor of 5, a TE/TR value of 16/25 ms, a flip angle of 20 degree, and a dynamic scan time of 1.8 s. A small gel phantom placed beside the mouse was used to monitor the magnetic drift for temperature correction. Mice were flushed before sacrifice and tumor tissue was removed for evaluation. Tumor drug uptake was evaluated by fluorescence microscopy and high performance liquid chromatography (HPLC).

Results and Discussion

The median increase in tumor doxorubicin concentration in the treated region is 9-fold greater than the concentration in untreated regions of the tumor (up-to a maximum 16-fold increase). Figure 3 shows the concentration of drug in tissue measured by HPLC for HIFU treated and untreated tumors (Fig. 3A) as well as fluorescence microscopy images qualitatively demonstrating the difference in drug concentration in untreated (Fig. 3B) and treated (Fig. 3C) regions of the tumor in the same animal. Fluorescence evaluation of the tumor tissue revealed increased focal nuclear uptake of Dox in regions treated with MR-HIFU hyperthermia with systemically administered Dox loaded TSLs. Quantitative measurement of tissue drug concentrations using HPLC, indicated an increase in Dox uptake from TSL compared to free Dox and Dox loaded TSLs without hyperthermia application.

Conclusions

This method provides precise and non-invasive hyperthermia treatment in a small animal using a clinically available MR-HIFU system. The combination of hyperthermia with Dox loaded TSLs resulted in higher concentration of doxorubicin compared to free Dox and Dox loaded TSLs without hyperthermia. These results are encouraging as we move into survival studies. The clinical translation would offer a new non-invasive and local treatment option for this type of cancer.

Acknowledgements

This work was supported by NIH grants R01 CA154451 and R01 CA188654.

References

1. T. Ades, R. Alteri, C. Barnes, T. Betaut, S. Bogdan, D. Brooks, G. Bunin, Wi. Chambers, C. DeSantis, T. Gasles, S. Gapstur, K. Grober, A. Henning, J. Angela, R. Kirch, J. Kramer, A. Liber, and J. Lortet-Tieulent, “Cancer Facts and Figures 2014,” American Cancer Society, Inc, 2014.

2. B. Hildebrandt, “The cellular and molecular basis of hyperthermia,” Crit. Rev. Oncol. Hematol., vol. 43, no. 1, pp. 33–56, Jul. 2002.

3. A. Partanen, P. S. Yarmolenko, A. Viitala, S. Appanaboyina, D. Haemmerich, A. Ranjan, G. Jacobs, D. Woods, J. Enholm, B. J. Wood, and M. R. Dreher, “Mild hyperthermia with magnetic resonance-guided high-intensity focused ultrasound for applications in drug delivery.,” Int. J. Hyperthermia, vol. 28, no. 4, pp. 320–36, Jan. 2012.

4. N. Hijnen, S. Langereis, and H. Grüll, “Magnetic resonance guided high-intensity focused ultrasound for image-guided temperature-induced drug delivery.,” Adv. Drug Deliv. Rev., vol. 72, pp. 65–81, Jun. 2014.

Figures

Figure 1. Planning and temperature mapping for image-guided hyperthermia (Left). The KPC tumor was clearly identified on the planning images on the tail of the pancreas (Left). Real-time temperature monitoring using the proton resonance frequency shift (PRFS) method shown in color overlaid on the planning image (Right).

Figure 2. Representative example of temperature elevation during a sonication following a short heat up period, stable mild hyperthermia was achieved in the target region through binary feedback control. Algorithm was programmed to keep temperature between 41-42.5 °C within ROI (ROI 4 mm). Golden vertical bars represent the start and end of sonication.

Figure 3. (A) Doxorubicin concentration in the tumors of KPC mice. ThermoDox (TDox) group was treated with ThermoDox followed by hyperthermia. ThermoDox control (Tdox control) was administered ThermoDox but not exposed to HIFU. Free Dox group received the equivalent dose of free doxorubicin systemically (not in liposomal form). (B) Tumor in region that was not exposed to hyperthermia. (C) Tumor in region that was exposed to hyperthermia. (scale bar = 100 µm)



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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