Utility of Positron Emission Tomography (PET) Scanning in Managing Patients with Hodgkin Lymphoma

Use of positron emission tomography (PET) or PET/ computed tomography (CT) in Hodgkin lymphoma (HL) continues to expand worldwide. PET is currently widely utilized for response assessment after completion of therapy and, to a lesser extent, for pretreatment staging and assessment of response during therapy (therapy monitoring). In pretreatment staging, PET cannot replace CT or bone marrow biopsy (BMB); however, it can provide complementary information to both CT and BMB, potentially resulting in a modification of disease stage (usually upstaging) in about 15–20% of patients with impact on management in about 5–15%. PET for response assessment at the conclusion of treatment is substantially more accurate than CT because of its ability to distinguish between viable tumor and necrosis or fibrosis in posttherapy residual mass (es) that are present in about two-thirds of patients with HL without any other clinical or biochemical evidence of disease. PET, therefore, provides more accurate response classifications compared with CT-based assessment. The role of PET for therapy monitoring is still evolving but may prove to be the most exciting with potentially high impact on patient management and outcome. PET evaluation during therapy appears to be at least as accurate for predicting patient outcome as evaluation after completion of therapy and its use is clearly justified if the purpose is to provide an early and yet accurate assessment of response with the clear intent of tailoring therapy according to the information provided by the scan. The role of PET scanning for post-therapy surveillance without clinical, biochemical or radiographic evidence of disease remains controversial, primarily because of the potential for a disproportionate fraction of false-positive findings, potentially resulting in increasing cost without proven benefit from earlier PET detection of disease compared to standard surveillance methods. Large prospective studies are therefore needed to determine whether routine surveillance by PET is both cost-effective and whether it results in meaningful changes in patient management and/or outcome.