Image Guided Radiation Therapy (IGRT)

Sophisticated imaging techniques allow radiologists to administer higher doses of radiation to a tumor without increasing the risk of toxicity for the patient. Image-guided radiation ensures better coverage of the tumor and less collateral irradiation of surrounding healthy tissue.

Radiation therapy is an established cancer treatment modality, and mesothelioma specialists often integrate external beam radiation into aggressive treatment plans. However, safely administering radiation to mesothelioma patients is a challenge for radiologists.

The vast majority of mesothelioma tumors form close to extremely sensitive vital organs such as the lungs, heart, liver, intestines and kidneys. This positioning also means mesothelioma tumors may move whenever the patient breathes or their abdominal organs shift because of digestion.

Image-Guided Radiation Therapy Facts

  • Mesothelioma is challenging for radiologists to safely target for treatment.

  • Devices combining imaging and therapy increase the accuracy of radiation therapy.

  • 4-D imaging accounts for the motion of the tumor site as the patient breathes.

  • Image-guided radiation therapy is available only at specialized treatment centers.

Radiologists must make a trade-off between treatment effectiveness and safety. A higher dose of radiation will kill more cancer cells, but it could also cause severe complications if it hits healthy cells by mistake.

Modern technologies such as intensity-modulated radiation therapy and proton therapy can target areas in the body much more selectively, but these therapy techniques are still only as good as the imaging scans that guide them. This is where the emerging techniques of image-guided radiation therapy (IGRT) come in.

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Combining Imaging and Therapy Devices

IGRT involves performing imaging scans immediately before or during every radiation therapy session. This way, the radiologist can adjust the treatment if the tumor site’s position has changed or the patient has lost or gained weight.

In 2000, Siemens unveiled a computed tomography (CT) scanner that could be installed alongside a linear accelerator in the same room, making it possible to take an imaging scan and administer radiation without moving the patient.

Two years later, Accuray introduced the TomoTherapy System, a single machine that can perform CT scans and administer intensity-modulated radiation therapy.

More recently in 2015, doctors hailed the development of the first combination linear accelerator and magnetic resonance imaging (MRI) machine.

Although these types of combination devices have become more common in the past decade, in many cases cancer patients still receive imaging scans and radiation therapy on different days and in different facilities.

Research has shown this is not ideal. Lung cancer presents many of the same targeting problems as pleural mesothelioma, and a 2016 study of 91 patients with lung cancer revealed daily imaging scans during radiation therapy was associated with a longer median survival time than weekly imaging scans.

4-D Imaging of Moving Tumors

Even when a doctor performs an imaging scan before a radiation treatment, the static scan might not account for the motion of the tumor site and the vital organs in the body. Specialists developed four-dimensional imaging to address this problem.

In 4-D imaging, the fourth dimension is time, which allows doctors to track the cyclical path of the tumor site’s position in the body as the patient breathes. You could think of this as a 3-D video of the inside of the chest that plays on a loop, showing doctors how organs move when the patient inhales and exhales.

A radiologist could use 4-D imaging to ensure the most intense radiation stays confined to the tumor site. Alternatively, they could synchronize the aim of the radiation machine to the motion of the target in the body.

Image-Guided Radiation Therapy for Mesothelioma

Cancer treatment teams face two main obstacles to using IGRT: The high cost of the technology and the high level of experience required to use it.

As with all types of cancer treatment, the best hope for mesothelioma patients is to go to one of the top cancer centers in the country that specialize in asbestos-related illnesses.

Another drawback is IGRT causes each therapy session to take longer — perhaps 90 minutes rather than 30. However, many experts expect the average IGRT session duration to shorten as radiation therapy technology continues to improve.

Remember, only an experienced mesothelioma specialist can determine whether any type of radiation therapy is an appropriate treatment modality. Mesothelioma is a rare and complex form of cancer, and every case requires an individualized treatment plan.

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Karen Selby

Karen Selby joined Asbestos.com in 2009. She is a registered nurse with a background in oncology and thoracic surgery and was the director of a tissue bank before becoming a Patient Advocate at The Mesothelioma Center. Karen has assisted surgeons with thoracic surgeries such as lung resections, lung transplants, pneumonectomies, pleurectomies and wedge resections. She is also a member of the Academy of Oncology Nurse & Patient Navigators.

Sources
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  7. Teoh, M. et al. (2011, November). Volumetric modulated arc therapy: a review of current literature and clinical use in practice. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3473700/
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