Prevalence and Significance of FDG-avid Mediastinal Lymph Nodes in Patients with Colorectal Cancer in a Tuberculosis-endemic Area

Abstract

Objective: To find prevalence and causes of fluorodeoxyglucose (FDG)-avid mediastinal lymph nodes in patients with colorectal cancer in a tuberculosis-endemic area.Material and Methods: For this study we enrolled patients with colorectal cancer who underwent Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT). Then, PET/CT images were reviewed by a nuclear medicine physician to find mediastinal lymph nodes with FDG uptake beyond the lung background defined as FDG-avid node. The degree of FDG uptake was graded and measured, and associated factors for presence of FDG-avid nodes were evaluated. The causes of FDG-avid nodes were also determined.Results: A total of 109 patients (64 males; mean age 61.2 years) were studied. Seventy-five patients had FDG-avid mediastinal nodes; accounting for a prevalence of 68.8% (95% CI: 59.2-77.3%). Most of the patients had multiple and bilateral nodes; with the zones of hilar and interlobar being the most common location. Age ≥50 years was the only associated factor for FDG-avid nodes (OR of 3.16, p-value=0.035). Only one out of the 32 patients (with fulfilled followup criteria) had a metastatic node.Conclusion: The prevalence of FDG-avid mediastinal nodes in colorectal cancer patients in a tuberculosis-endemic area was significantly high. Most of the lesions were benign in nature; thus, interpretation of these findings should be considered carefully to avoid false-positive results.