18FDG PET in lymphoma

Abstract

18F-FDG PET/CT has become essential in the management of patients with Hodgkin’s and non-Hodgkin’s lymphoma. The utility of 18F-FDG PET/CT imaging is based upon increased anaerobic metabolism of neoplastic tissue. The degree of hypermetabolism is somewhat proportional to lymphoma grade. Based on the ability of 18F-FDG PET/CT to identify hypermetabolic tissue, it has greater sensitivity and specificity for the detection of tumors in general and lymphoma in particular compared to CT or MRI. 18FFDG PET/CT has made a significant impact in lymphoma management in the following instances: 1. Extent of disease in patients already diagnosed with lymphoma; 2. Identification of hypermetabolic disease in lymphadenopathy identified by other means; 3. Evaluation of response to therapy - with greater specificity than CT alone; 4. Early detection of recurrent disease; 5. Identification of transformation from low grade to high-grade lymphoma; 6. Prediction of response to therapy and prognosis. In many clinical trials, 18F-FDG PET/CT has replaced CT as the standard for assessment of residual disease. It has become a standard procedure at the time of initial diagnosis and following completion of therapy as well at 6-24 month intervals during the follow-up or upon the recurrence of symptoms suggestive of relapse. On an investigational basis, we have demonstrated that resolution of lymph node hypermetabolism, as early as following a single cycle of chemotherapy, is predictive of a prolonged disease-free interval whereas failure to respond after a single cycle indicates that even if there is resolution of disease after completion of a full course of treatment, relapse occurs earlier. If confirmed by additional studies, early 18F-FDG PET/CT evaluation of response may provide a basis to select patients for a change to more aggressive or alternate therapy. In fact, it may also identify a sub-population of patients who do not require an extended course of chemotherapy.