PET Scans More Effective Than CT in Lymphomas

PET Scans More Effective Than CT in Lymphomas

According to a recent article published in the British Journal of Cancer, positron emission tomography (PET) scans are more effective at detecting residual cancer after therapy than computed tomography (CT) scans in patients with Hodgkin’s disease (HD) or non-Hodgkin’s lymphoma (NHL).

Hodgkin’s disease and NHL are both cancers that affect cells of the immune system. The cancerous cells grow and replicate in an uncontrolled manner, inhibiting normal cellular growth of other immune cells, as well as crowding areas of the lymph system, such as lymph nodes, spleen and/or circulating blood. Treatment for HD or NHL typically consists of different regimens of chemotherapy and/or radiation therapy. Following therapy, patients undergo screening measures including scans to determine if treatment has eradicated all visible cancer or if any residual cancer is remaining. Results from these scans affect further treatment decisions, so their accuracy is imperative in obtaining optimal long-term results.

PET scans are emerging as a standard type of screening to be used in certain cancers; however, clinical trials are still comparing PET scans to other standard scans, such as CT scans, magnetic resonance imaging (MRI) scans, and ultrasound to determine their true clinical effectiveness. PET scans involve a mixture of sugar attached to a radioisotope (a compound that continuously emits radiation for a specific period of time). This mixture is delivered into a vein of the patient prior to the scan. Cancer cells have a higher metabolic rate than normal cells, so they tend to “take up” the sugar/radioisotope mixture more readily than normal cells. The concentrated areas of radioactivity in cancerous areas are displayed on an image and read by a radiologist.

Recently, researchers from Italy conducted a clinical trial to directly compare the accuracy of PET scans to CT scans in the detection of residual cancer in patients with HD or NHL who had received prior treatment. This trial included 41 patients with HD and 34 patients with NHL who had been treated with initial therapy. Both PET and CT scans were performed and results were compared. Areas of suspicion were biopsied (a sample of tissue was removed and observed under a microscope) to determine definitive results. Of the 59 patients who did not have a suspicious area on a PET scan (negative results), not one experienced a cancer recurrence. Of these 59 patients, 30 had a suspicious area on a CT scan (positive results). In addition, 5 patients had positive PET scan results and negative CT scan results. Four of these 5 patients had a cancer recurrence according to biopsy results.

The researchers concluded that PET scans are significantly more accurate than CT scans at detecting residual cancer following initial therapy in patients with HD and NHL and should be utilized in the management of HD and NHL. Patients with HD or NHL may wish to speak with their physician about their individual risks and benefits of utilizing PET scans in the clinical management of their disease.

Reference: Zinzani PL, Fanti S, Battista G, et al. Predictive role of positron emission tomography (PET) in the outcome of lymphoma patients. British Journal of Cancer. 2004; 91: 850-854.

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