Positron emission tomography (PET) appears superior to other forms of imaging for accurately determining the extent of cancer in patients with Hodgkin’s disease, according to a recent article published in the journal
Cancer. This is important as treatment decisions for Hodgkin’s disease are based on the observed extent of the cancer.
Hodgkin’s lymphoma is a cancer of the lymph system, which is part of the immune (infection fighting) system that includes blood vessels, bone marrow, lymph nodes and lymph vessels that are present throughout the body. It also includes organs such as the spleen, thymus and tonsils. This cancer is characterized by the presence of the uncontrollable growth and division of atypical white blood cells (immune cells) that crowd lymph tissue, suppressing the formation and function of other cells normally found in this tissue. Hodgkin’s disease usually begins in a single lymph node and is capable of spreading throughout the body. Before treatment can begin, the stage, or extent of the disease needs to be determined, as the extent of disease dictates treatment options.
Computerized tomography (CT scans), magnetic resonance imaging (MRI) and conventional x-rays are all standard imaging techniques for initial staging and monitoring of treatment in Hodgkin’s disease. However, these imaging techniques are not very accurate at distinguishing between dead tissue and active cancer cells in the body. PET scans, on the other hand, are emerging as a type of imaging technique that appears to be superior to conventional imaging in accurately identifying active cancer cells in a variety of cancers. PET scans are able to distinguish between dead tissue and active cancer cells by exploiting a biological characteristic of rapidly dividing cancer cells – the metabolism of sugar. A solution containing a type of sugar attached to a radioactive compound is injected into the vein of a patient undergoing a PET scan. Cancer cells tend to take up more sugar than normal cells, so the solution becomes concentrated in the cancer. The attached radioactive compound emits a form of radiation that can be detected by the PET scanner. The scanner then forms a picture that allows the physician to see the location of small amounts of cancer cells if they exist.
Researchers from Germany recently conducted a clinical trial evaluating the accuracy of PET scans in 81 patients with Hodgkin’s disease. Patients were either being initially staged or were being monitored following treatment. In this trial, patients underwent PET scans as well as conventional imaging scans. Results were verified through biopsy results and/or follow-up evaluation. In newly diagnosed patients, PET was 96% accurate for determining the stage of disease, compared to only 56% accuracy for other imaging modalities. PET led to a lower stage classification in 28% of patients and a higher stage classification in 12% of patients when compared to conventional imaging results. In patients being monitored following treatment, PET was accurate in 91% of patients, compared with 62% when conventional imaging was used.
These results are consistent with a previous trial indicating that PET scans produce more accurate results in determining the extent of cancer in patients with Hodgkin’s disease. Patients with Hodgkin’s disease may wish to speak with their physician about the risks and benefits of undergoing a PET scan to most accurately determine the extent of disease and receive the most appropriate treatment. (
Cancer, Vol 91, No 2, pp 302-310, 2001)