Purpose: The purpose of this study was to evaluate the reliability of positron emission tomography (PET) in patients with follicular lymphoma (FL) after induction treatment.
Patients and methods: In all, 45 previously untreated patients with FL were studied with PET and computed tomography (CT) scans after chemotherapy induction treatment (fludarabine-containing regimens and CHOP [cyclophosphamide/doxorubicin/vincristine/prednisone] chemotherapy). Histopathologic analysis was performed when considered necessary.
Results: After treatment, 4 of 5 patients (80%) who had CT-negative/PET-positive findings experienced relapse/progression, compared with only 1 of 22 patients (4.5%) in the CT-negative/PET-negative subset. Among the 18 patients with CT-positive findings, all 6 patients (100%) who had PET-positive findings experienced relapse or progression, compared with 1 of 12 patients (8.3%) who had PET-negative findings. The 2-year progression-free survival rates were 20% and 90% in the CT-negative/PET-positive and CT-positive/PET-negative subsets, respectively (P = 0.0031). During the follow-up, 2 patients, who presented a PET positivity with a negative CT scan, underwent a lymph node biopsy, which confirmed the presence of FL infiltration.
Conclusion: In patients with FL, persisting PET positivity is predictive of early disease progression, because it is still highly likely that patients with PET-negative findings will ultimately progress, but this has not yet been manifested during the period of observation.