The role of positron emission tomography (PET) in the management of lymphoma patients

Background: Treatment of both Hodgkin's disease (HD) and aggressive non-Hod gkin's lymphoma (NHL) with abdominal presentation at the time of diagnosis is often followed by detection of residual masses by computed tomography (C T). However, CT is usually unable to disciminate between residual tumor and fibrosis/necrosis. We investigated the ability of fluorine-18 fluorodeoxyg lucose positron emission tomography (PET) to differentiate between residual active tumor tissue and fibrosis. Patients and methods: Forty-four patients with HD or aggressive NHL present ing abdominal involvement (41% with bulky mass) were studied with CT and PE T at the end of chemotherapy +/- radiation therapy. Results: After treatment, seven patients had negative PET and CT, and none of them relapsed. The remaining 37 patients all had positive CT (abnormalit ies less than or equal to 10%). All of the 13 who also had positive PET rel apsed (100%). By contrast, there was only 1 (4%) relapse among the 24 patie nts who were positive at CT but negative at PET. The two-year actuarial rel apse-free survival rate was 95% for those with negative PET compared with 0 % for positive PET patients (P < 0.000000). Conclusions: In lymphoma patients with abdominal masses who present CT posi tivity at restaging, PET should be considered the noninvasive imaging modal ity of choice for differentiating early recurrences or residual disease fro m fibrosis.