False-Positive 18F-FDG PET/CT Imaging: Dramatic "Flare Response" After Rituximab Administration

Area of Science:

• Oncology
• Nuclear Medicine
• Immunotherapy

Background:

• Non-Hodgkin lymphoma (NHL) treatment often involves chemotherapy combined with rituximab.
• Positron Emission Tomography/Computed Tomography (PET/CT) with fluorodeoxyglucose (F-FDG) is a key imaging modality for staging and response assessment in lymphoma.
• Rituximab, a monoclonal antibody, targets CD20-expressing B-cells, crucial in NHL therapy.

Observation:

• A 45-year-old woman with NHL experienced disease progression on F-FDG PET/CT after R-ESHAP therapy.
• Lymph node biopsy revealed reactive changes, not lymphoma, despite positive PET/CT findings.
• This suggested a potential discrepancy between imaging and histological results.

Findings:

• The patient's F-FDG PET/CT scan indicated disease progression.
• Histopathological examination of lymph node biopsies showed only reactive changes, ruling out lymphoma.
• This discrepancy highlights a potential false-positive imaging result.

Implications:

• Rituximab therapy can induce inflammatory responses that mimic lymphoma progression on F-FDG PET/CT.
• Awareness of this potential for false-positive imaging is critical for accurate patient management.
• Confirmation of unexpected findings via biopsy is essential to prevent misdiagnosis and inappropriate treatment intensification.