Mesothelioma Diagnosis and Staging Through PET Imaging

Mesothelioma Diagnosis

Mesothelioma Diagnosis: Positron Emission Tomography (PET), the New Imaging Technology

Positron Emission Tomography scanning (PET) provides more information than x–rays or CT and MRI scans, detecting biological changes and extremely small cancerous tumors. Able to indicate whether a tumor is benign or malignant, PET scanning also shows the extent to which cancer has spread. It may be used to determine whether surgery is necessary or if treatment therapies are working.

How Does PET Work?

PET scanning uses a camera that produces powerful images of the body’s biological functions. Compounds such as sugars (glucose, for example) are labeled with a signal–emitting tracer and then are injected into the patient. A scanner that looks much like that used to obtain a CT image records the signals these tracers emit as they travel through the body and collect in various organs that are targeted for examination. A computer reassembles the signal into images that reflect the levels of uptake of the sugars.

Because cancers metabolize sugars at a higher rate than normal tissues or organs, the PET scan shows where there is abnormal activity and can pinpoint the areas of active disease. It differentiates scar tissue from tumor. It also can accurately image and measure the metabolic function of cancer to track the effects of radiation or chemotherapy, supplying doctors with information that can help avoid unnecessary surgery.

PET Use for Mesothelioma Diagnosis and Staging

PET has helped lung cancer patients avoid chest surgery by finding tumors that an operation would not remove (see PET Scans Detect Lung Cancer Spread, American Cancer Society). Medicare has approved its use in the diagnosis and staging of melanoma, lymphoma, and cancers of the lung, esophagus, colon, rectum, mouth and throat.

Recent studies indicate that PET holds great promise for diagnosing mesothelioma and determining mesothelioma staging, or the extent to which tumors have spread. At the University of Pennsylvania Medical Center, researchers evaluated 28 patients for mesothelioma using the sugar tracer fluoro–2–deoxy–D–glucose (FDG) and PET (Chest. 1998 Sep; 114(3): 713–22). In a comparison of PET imaging with thoracoscopy or surgical biopsies, PET successfully indicated the presence of disease in 24 patients, and of benign conditions in the other four. The uptake of FDG was significantly higher in diseased cells, and PET analysis also showed tumors in the lymph nodes of 9 patients. The lymph nodes appeared normal in CT scans.

Another study at Brigham and Women’s Hospital and Harvard Medical School in Boston traced 15 patients, 11 of whom had mesothelioma and four who were disease–free (J Nucl Med. 2002 Sep; 43(9): 1144–9). PET results were compared with laboratory analysis of biopsied fluids and tissues. PET detected all 11 primary tumors, and confirmed the absence of disease in the other four patients. Out of 28 disease–positive lesions, PET accurately detected 27.

These studies indicate that although CT scans are a standard test for mesothelioma patients, PET also has a role in mesothelioma diagnosis. Whether or not you should have a PET scan is a decision that should be discussed with your doctor. He or she will make a judgment based on your particular case and your other test results.