Abstract
1194
Objectives: dentify Sarcoi-like reaction in cancer patients receiving Chemotherapy and Immunotherapy: get out of the weeds of SUVmax Yang Lu, Homer A. Macapinlac Department of Nuclear Medicine, Division of Diagnostic Imaging, The University of Texas MD Anderson Cancer Center. Background: FDG is not a cancer-specific agent and can accumulate in benign processes such as infection or granulomatous inflammation producing false positive results. Accurate interpreting FDG PET/CT is important to determine cancer prognosis and choose appropriate treatment. FDG can accumulate in benign processes such as infection or granulomatous inflammation producing false positive results. Relatively symmetric FDG-avid bilateral hilar and mediastinal lymph nodes in a “lambda”, “Christmas Tree” or “butterfly” distribution pattern, which we defined as “sarcoid-like” distribution pattern, are not uncommonly observed on FDG PET/CT but with different interpretation among different physicians, especially for the lymph nodes demonstrating high SUV (SUV >2.5). This case presentation is to illustrate that FDG distribution pattern is more important than SUVmax in interpretation of PET/CT; and thoracic lymph nodes in a “sarcoid-like” distribution pattern on PET/CT are benign regardless of the SUVmax value. Methods: In addition to biopsy-proven sarcoidosis cases who have no history of cancer, we selected typical PET/CT studies performed in cancer patients with minimal 12 months clinical and imaging follow-up, and/or definitive pathology results shown sarcoidosis. Cancer patients with “sarcoid-like” chest lymph nodes distribution pattern on series FDG PET/CT were compared with non-cancer, sarcoidosis only patients’ FDG PET/CT.
Results: There is similar distribution pattern of FDG avid thoracic lymphadenopathy between noncancer sarcoidosis patients and cancer patients who had chemotherapy and/or immunotherapy induced sarcoid-like reaction. Sarocoidosis and/or sarcoid-like reaction can involve multiorgans including lymph nodes, lung, cutatenous nodules, liver, spleen, and heart. The SUVmax of these lymph nodes varies from 2.4 to 17.7 in our cases. Sarcoid-like reaction in cancer patients persists up to 2+ years even in off-therapy observation course. Although FDG avidity of sarcoid-like reaction varies in series PET/CT in the same patient, the distribution pattern and sizes of thoracic lymphadenopathy are grossly stable.
Conclusions: To avoid pitfall in PET/CT interpretation, it is important to recognize the sarcoid-like pattern of FDG uptake, which regardless of SUV value is favored to represent a benign rather than a malignant process.