Brain Tumor Diagnosis
Tumors that originate in the brain are a relatively rare form of cancer. More commonly tumors start in other organs such as the lung or breast and then metastatic disease spreads to the brain. Brain tumors are most often discovered because of symptoms that the patient has developed - symptoms caused by the degeneration of function in the area of the brain that the tumor is forming.
Once discovered, differentiating between primary brain tumors and metastatic disease is a key diagnostic point, and is confirmed by biopsy. Pinpointing the exact location to biopsy is difficult and can carry some risks, and physicians increasingly rely on medical imaging to help. MR and CT scans of the brain are used to look at the brain when an abnormality is suspected. These give exquisite detail of the structure and anatomy of brain tumors, but by adding metabolic information from a PET/CT scan, the physician can make a more precise determination of the location and extent of disease.
Fortunately, not all brain tumors are cancerous. Benign tumors do not metastasize and, with very rare exceptions, are not life-threatening. Cancerous tumors are "graded" by their level of aggressiveness and by the type of cells from which they grew. By studying the results of the PET/CT scan, a physician can separate a tumor as being high-grade, low-grade or benign, based on the degree of uptake of the radiopharmaceutical. Elevated uptake in a brain tumor should be confirmed histologically, but is generally associated with a poorer prognosis compared with brain tumors with lower levels of FDG uptake.
Early determination of the grade of the tumor and how far it has spread helps the physician select the most appropriate treatment.
Source: Atlas of Clinical Positron Emission Tomography by Sallie F. Barrington, Michael N. Maisey and Richard R. Wahl. Oxford University Press, Inc. New York, NY. 2006.