Cytoreductive Surgical Treatment of Pleural Mesothelioma in a Porcine Model Using Magnetic-Resonance-Guided Focused Ultrasound Surgery (MRgFUS) and Radiofrequency Ablation (RFA)

Our plain-English summary of Cytoreductive Surgical Treatment of Pleural Mesothelioma in a Porcine Model Using Magnetic-Resonance-Guided Focused Ultrasound Surgery (MRgFUS) and Radiofrequency Ablation (RFA), by M. Costa, C. Fernandes, M. Eames, et al (Tomography, 2022).

The study

• Authors: M. Costa, C. Fernandes, M. Eames, A. Hananel, J.P. Mugler, J. Huaromo, J.B. Yang, J. Mata
• Journal: Tomography
• Published: 2022;8(5):2232-2242
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A combination of surgery and chemotherapy is the most effective treatment available for Malignant Pleural Mesothelioma (MPM). However, both cause significant collateral damage and cannot eliminate residual microscopic disease. This investigation aimed to compare and determine the feasibility of utilizing Radiofrequency Ablation (RFA) and Magnetic-Resonance-guided Focused Ultrasound Surgery (MRgFUS) as alternative treatments for MPM. A large animal tumor model was developed in 13 Yorkshire female pigs using the MSTO211H cell line. Two pigs were initially used to determine the cyclosporine dose required for immunosuppression and tumor development. Subsequently, 11 other pigs underwent tumor development. Of these 11, 2 died during cell inoculation. Small tumor masses and adhesions were present in the other 9, indicating mesothelioma development. Five pigs then received RFA treatment, and 4 pigs received MRgFUS treatment. Tumor model development and effect of the two treatments were examined using MRI and by necropsy. RFA and MRgFUS both successfully ablated approximately the same sized area in the same treatment time. This study demonstrates that RFA and MRgFUS are feasible for tumor debulking, and while MRgFUS requires more pretreatment planning compared to RFA, MRgFUS is a completely noninvasive procedure.

In plain English

This was an animal experiment, not a study of asbestos exposure. It tested two heat treatments on a pig model of pleural mesothelioma: needle-based radiofrequency ablation (RFA) and incision-free magnetic-resonance-guided focused ultrasound surgery (MRgFUS). The researchers immunosuppressed 13 female Yorkshire pigs with cyclosporine and injected human mesothelioma cells (MSTO211) into the right chest. Two pigs died right after the injection. In pigs followed afterwards, MRI showed pleural effusion (fluid around the lungs) and thickening of the pleura, diaphragm and heart lining. The authors reported that 81% of the pigs examined at necropsy developed adhesions. Large tumor masses were not seen, so the authors changed the RFA objective from treating tumor masses to breaking the adhesions. Five pigs received RFA and four received MRgFUS. The authors reported RFA ablations of more than 2 cm in about 30 minutes. MRgFUS lesion sizes varied, and at necropsy they sometimes differed from the MRI picture. The authors concluded that both techniques were feasible and gave similar-sized ablations. They noted that without microscopic tissue analysis a pure mesothelioma model could not be confirmed, and that a larger study is needed.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Pilot animal experiment (porcine tumor model) comparing two ablation treatments
• Who was studied: 13 female Yorkshire pigs (about 11 kg) at the University of Virginia. Two were control pigs used to set the cyclosporine dose. The other 11 were treatment pigs: 2 died after inoculation, 5 received RFA and 4 received MRgFUS.
• Exposure: No asbestos exposure. Pigs were immunosuppressed with oral cyclosporine (10 mg/kg/day in the 2 control pigs, 20 mg/kg/day in the treatment pigs) and injected with the human mesothelioma cell line MSTO211 in the right lower chest. They were then treated with percutaneous RFA or MRgFUS.
• Main results:
  • Pigs #5 and #11 died immediately after the cell injection procedure
  • Pleural effusion, the most prominent MRI sign of the model, was seen at several time points in the pigs followed by MRI after inoculation (the article says 'all pigs')
  • Pleural, diaphragm and pericardium thickness increased in all animals followed. The authors considered it unlikely that the pericardium change was caused purely by the disease model.
  • At necropsy, 81% of the pigs had developed adhesions; the article gives no denominator. Pigs #1 and #4 showed no adhesions.
  • Large tumor masses were not seen in the lung pleura, so the objective of the RFA treatment was changed from treating tumor masses to breaking adhesions
  • RFA (5 pigs): the authors reported ablations of more than 2 cm in about 30 minutes. In pig #4 the ablations measured 1.9 cm (left) and 2 cm (right) in diameter.
  • MRgFUS (4 pigs): total treatment time, including MRI, was about 15 minutes
  • MRgFUS lesion sizes on MRI and at necropsy did not always match. In pig #8 the necropsy lesion was much larger than it appeared on MRI (MRI 1.5 by 1.3 cm). In pig #10 MRI showed about 1.4 by 1.4 cm, but necropsy showed a small ablation under 1 cm. In pig #12 MRI showed 2.4 by 1.6 cm and necropsy showed a 3 by 1.5 cm elongated lesion.
• The authors' conclusion: The authors concluded that both MRgFUS and RFA were feasible for ablating the pleura and gave ablation areas of roughly similar size. They noted that MRgFUS needs no incisions but requires more pretreatment planning.
• Limitations the authors state:
  • The thickened pericardium and diaphragm were not examined microscopically, so the authors could not definitively conclude that a pure mesothelioma model was created
  • A cyclosporine supply interruption meant animals could not be immunosuppressed for longer than 12 weeks, and some were stopped earlier
  • Pericardial fluid may have been measured together with the pericardium, giving higher thickness values
  • The RFA probe was not MRI compatible and was guided by fluoroscopy, so targeting was not always precise
  • No necropsy was performed on the two pigs that died after inoculation
  • A study with more animals is needed to obtain statistical significance

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Cytoreductive Surgery, Pleural Mesothelioma, Ultrasound, Chemotherapy, Mesothelioma, Autopsy.

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