Current State and Future Directions of Pleural Mesothelioma Imaging
Source: Armato III SG, et al., Current state and future directions of pleural mesothelioma imaging, Lung Cancer (2007), doi:10.1016/j.lungcan.2007.09.027
Imaging is one of the most important aspects of cancer diagnostics. It allows the physician team to look at—and respond to—a number of different aspects of a person’s disease, including tumor extent, invasion of distant body spaces, treatment response, as well as a host of other issues. There are a number of different technologies in use and each one has its own particular strengths and weaknesses that will impact the manner in which it is used and the efficacy of the results it will return. Along with these individual modalities, the form of cancer that is being imaged will also affect the results that are obtained. Certain forms of cancer are simply easier to image than others. Mesothelioma, especially pleural mesothelioma, remains one of the more difficult cancers to image as it is primarily a diffuse disorder that affects tissue that surrounds large areas of the body.
Research is on-going regarding the most efficient use of the various imaging modalities for mesothelioma. A report has recently been released that assesses the strengths and weaknesses of current techniques and notes some future directions that may positively impact the imaging of mesothelioma.
The two most common imaging techniques used for mesothelioma imaging are computed tomography (CT) scans and positron emission tomography (PET) scans. Magnetic Response Imaging (MRI) is also used but CT and PET, as well as variations common to both, are the major techniques that will be covered here.
Computed Tomography (CT) Scans
CT is the primary imaging technology used in the diagnosis and staging of mesothelioma. It can be used to scan the entire pleural surfaces and is effective at identifying areas of benign vs. malignant tissue, at charting overall tumor morphology and can be effective at identifying local tissue invasion. It is not, however, effective at identifying the malignant status of the lymph nodes, so other techniques need to be used to investigate nodal status.
Position Emission Tomography (PET) Scans
PET functions by tracking how the body uses glucose. Tumors consumer sugar at a different rate than the rest of the body does, so PET scans are used to identify areas where sugars are over-consumed. FDG (fluorodeoxyglucose) is the molecule most often used in PET scans to measure tumor activity. PET scans are effective at identifying distant areas of tumor growth, but they suffer from poor spatial resolution so they are not effective at determining invasion into local surfaces. They do, however, show promise in the measurement of overall tumor response.
Integrated PET/CT has proven to be a real advance on the individual modalities. Precise registration of the two scans allows a deeper look at the underlying anatomic and functional structures at work. PET/CT is especially good at detecting the extent of disease involvement and in detecting distant metastases. It can also be used to identify lymph node status in the mediastinum, which is an area of connective tissue in the central chest that contains the heart, esophagus, trachea, and thymus. As such, PET/CT is useful as a preoperative technique to evaluate mesothelioma patients who may be candidates for curative surgery, such as extrapleural pneumonectomy.
Molecular bioprobes are a relatively new area of research, but they hold great promise for imaging mesothelioma, as well as other cancers. The idea behind these bioprobes is they attach an antibody to mesothelioma cells that allows for more precise imaging of the actual biochemical and physiological changes that are taking place in the body. While standard imaging modalities are only able to measure the actual structural changes that emerge from the underlying biology, molecular bioprobes should allow doctors to see what is happening on a deeper level.
Mesothelioma remains one of the most difficult of all cancers to manage. Its complex biology makes imaging especially difficult. There is not a single imaging method that can be used without compromise, so doctors and other scientists are actively engaged in research to create more efficient imaging modalities. The paper that was covered in this news post was an attempt to quantify the current status of imaging techniques used in the diagnosis and staging of pleural mesothelioma. While much more research needs to be done, there is hope that new methods will allow more effective treatment of patients with this difficult disease.