FDG PET/CT in the diagnosis of rituximab-induced lung disease

Learning Objectives Rituximab induced lung disease is rare but serious side effect with a mortality rate of 30%. A nuclear medicine phyician hould be familiar with PET/Ct pattern and clinical context of this complication.

A 23-year-old man with stage IV ES diffuse large B cell lymphoma (DLBCL) presented for the sixth cycle of chemotherapy, rituximab, cyclophosphamide, doxorubicin, and prednisone (R-CHOP). He was complaining of recent onset shortness of breath, fever and dry cough. A chest X-ray (Fig. A) revealed bilateral infiltrates. The patient was started on broad spectrum antibiotic and antifungal therapy. The patient did not respond to therapy well. A computerized tomography (CT) demonstrated multifocal bilateral patchy airspace opacity with no evidence of pulmonary embolism (Fig. B). Subsequently, the patient had PET/CT scan (Fig. C) that showed intensely hypermetabolic (SUV max 11.9) bilateral patchy lung opacity. The patient underwent bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsies. BAL revealed no evidence of viral cytopathy, acid -fast bacilli or fungal yeasts. Biopsy revealed mild interstitial acute and chronic inflammation as well as reactive alveolar epithelial changes. Subsequently, the patient was started on steroid therapy and responded well (Fig. D). The possible role of FDG uptake in the diagnosis of rituximab induced lung disease has been reported before (1, 2). FDG uptake was reported to precede CT changes as well (2, 3). In this case, the PET/CT demonstrated diffuse lung inflammation in DLBCL patient treated with R-CHOP regimen presenting with respiratory symptoms.