When should FDG-PET be used in the modern management of lymphoma?

Positron Emission Tomography (PET) is a functional imaging technique that, combined with computerized tomography (PET-CT), is increasingly used in lymphoma. Most subtypes accumulate fluorodeoxyglucose (FDG) and the increased sensitivity of PET-CT, especially for extranodal disease, compared to CT, makes PET-CT an attractive staging tool. The availability of a staging PET-CT scan also improves the accuracy of subsequent response assessment. 'Interim' PET-CT can be used to assess early response and end-of-treatment PET-CT assesses remission. Clinical trials are currently seeking to establish whether the predictive value of PET-CT can be successfully used to guide individual treatment to reduce toxicity and/or to improve outcomes. Standardized methods for performing and reporting PET have been developed in the context of trials. The role of PET in transplantation selection is currently evolving, as it appears to be more accurate and prognostic than CT. The role of FDG PET-CT throughout the management course in patients with lymphoma is explored in this review, with areas discussed that may limit the use of PET-CT imaging which clinicians should be familiar with to inform practice.

PET-CT staging of DLBCL accurately identifies and provides new insight into the clinical significance of bone marrow involvement.

We investigated whether positron emission tomography combined with computed tomography (PET-CT) identifies clinically important bone marrow involvement by diffuse large B-cell lymphoma (DLBCL) with sufficient accuracy to replace routine staging bone marrow biopsy. All patients from a single centre diagnosed as DLBCL since 2005 had data extracted from staging PET-CT, marrow biopsy, and treatment records. Of 130 patients, 35 (27%) were judged to have marrow involvement; 33 were identified by PET-CT compared with 14 by marrow histology. PET identified all clinically important marrow lymphoma, while biopsy did not upstage any patient. Sensitivity and specificity were 94% and 100% for PET-CT and 40% and 100% for marrow biopsy. As a secondary aim, we compared the prognosis of marrow involvement, as detected by PET-CT or biopsy. Cases with marrow deposits identified by PET-CT but not biopsy had progression-free survival (PFS) and overall survival similar to stage IV disease without involved marrow. Positive biopsy conferred significantly inferior PFS (P = .003); these cases frequently had other markers of poor-risk disease. These data confirm that in experienced hands PET-CT has a high level of accuracy for identifying marrow disease in DLBCL, and provide new insight into the nature and clinical significance of marrow involvement.