PET/CT is the most useful test for determining the stage of cancer. It is more accurate than any other test in finding local or metastatic tumors. Although PET can't detect microscopic cells, it can detect clusters of tumor cells that metastasized, or spread, to other tissues or organs.
When comparing the abilities of CT and PET/CT to detect metastatic lymph nodes, the sensitivity, specificity, and accuracy of PET/CT were 71%–89%, 89%–96%, and 81%–93%, respectively. However, nodal staging requires accurate and reliable interpretation of the information provided by PET/CT.
If it looks as though there are still swollen (enlarged) lymph nodes after treatment, a PET-CT scan can help show if this is due to scar tissue or there are still active lymphoma cells.
PET scanning can help identify bone metastases at an early stage of growth before host reactions to the osteoblasts occur. FDG-PET scanning depicts early malignant bone-marrow infiltration because of the early increased glucose metabolism in neoplastic cells.
MRI (magnetic resonance imaging) uses radio waves and magnets to take pictures inside of your body. MRI can detect spinal cord damage or identify brain metastasis. PET scan (positron emission tomography) works to identify abnormalities anywhere in the body.
When observed under a microscope and tested in other ways, metastatic cancer cells have features like that of the primary cancer and not like the cells in the place where the metastatic cancer is found. This is how doctors can tell that it is cancer that has spread from another part of the body.
Not all cancers show up on a PET scan. PET scan results are often used with other imaging and lab test results. Other tests are often needed to find out whether an area that collected a lot of radioactive material is non-cancerous (benign) or cancerous (malignant).
A PET/CT scan can be more sensitive than other imaging tests and may find cancer sooner than other tests do. Not all tumors take up the radiotracer, but PET/CT is highly accurate in differentiating from the benign and malignant tumors it finds, particularly in some cancers such as lung and musculoskeletal tumors.
To metastasize, cancer cells break off from the primary tumor and travel through the blood or lymph to other organs. If someone is found to have cancer in their lymph nodes, it's usually a bad sign that the cancer has or will soon spread to other parts of the body. Most cancer deaths are caused by metastatic cancer.
Lymph nodes deep in the body cannot be felt or seen. So doctors may use scans or other imaging tests to look for enlarged nodes that are deep in the body. Often, enlarged lymph nodes near a cancer are assumed to contain cancer. The only way to know whether there is cancer in a lymph node is to do a biopsy.
More often, a cancer may appear in the lymph nodes as a metastasis, spreading from somewhere else in the body. Some cancer cells break off from a tumor and metastasize in another location. Those cancer cells may travel through the bloodstream and reach other organs, or go through the lymph system and reach lymph nodes.
PET scanning can give false results if chemical balances within the body are not normal. Specifically, test results of diabetic patients or patients who have eaten within a few hours prior to the examination can be adversely affected because of altered blood sugar or blood insulin levels.
PET scans are more accurate than biopsy for cancer diagnosis. They can detect very small tumors that would not be detectable on a biopsy.
When the scan lights up brightly, it means there is metabolic activity. Most aggressive cancers light up brightly, but the caveat is inflammation in the body also lights up because inflammatory cells are also metabolically active. That's why we need to verify the scan results with a needle biopsy.
PET scans may play a role in determining whether a mass is cancerous. However, PET scans are more accurate in detecting larger and more aggressive tumors than they are in locating tumors that are smaller than 8 mm a pinky nail (or half of a thumb nail) and/or less aggressive cancers.
Therefore, PET is not specific for neoplastic states. If a lesion is identified by a PET scan, it may need to undergo a biopsy to determine benign nature versus malignancy.
In general, PET scans may be used to evaluate organs and/or tissues for the presence of disease or other conditions. PET may also be used to evaluate the function of organs, such as the heart or brain. The most common use of PET is in the detection of cancer and the evaluation of cancer treatment.
After the Scan
It wears off with time and is not directly harmful to others. Drinking a lot of water may help the radioactive material leave your body quicker. If you had a sedative to relax during the procedure, you should have someone drive you home and stay overnight with you.
It's possible to have cancer even if the PET scan is negative. That's because cancer cells may not be emitting enough of the radioactive substance for the PET scan to detect them. In addition, other conditions can cause false positive PET results.
A PET scan shows how organs and tissues are working. This is different than MRI and CT scans. These tests show the structure of, and blood flow to and from organs. Machines that combine the PET and CT images, called a PET/CT, are commonly used.
Most malignant tumors that metastasize do so within five years after the primary tumor has been detected, so this raises the question of how one can explain “dormancy” among tumor cells for decades.
Which Type of Cancer Spreads the Fastest? The fastest-moving cancers are pancreatic, brain, esophageal, liver, and skin. Pancreatic cancer is one of the most dangerous types of cancer because it's fast-moving and there's no method of early detection.
Pain is the most common symptom of bone metastases. It tends be a constant, aching pain that may be worse during activity and can cause sleeping difficulties.