Impacts of 18F-FDG PET/CT Parameters on Differential Diagnosis and Outcome of Patients with Primary Invasive Mucinous and Lepidic Predominant Adenocarcinoma of the Lung.

Objectives: The purpose of this study was to investigate whether ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) parameters have a role in differentiating invasive mucinous lung adenocarcinoma (IMA) from lepidic predominant lung adenocarcinoma (LPA). Additionally, we compared the ¹⁸F-FDG-PET/CT features between survivors and non-survivors.

Methods: Tumors were divided into 2 groups according to CT appearance: Group 1: nodular-type tumor; group 2: mass- or pneumonic-type tumor. Unilateral and bilateral multifocal diseases were detected. Clinicopathological characteristics and PET/CT findings were compared between IMAs and LPAs, as well as between survivors and non-survivors.

Results: We included 43 patients with IMA and 14 with LPA. Tumor size (p=0.003), incidence of mass/pneumonic type (p=0.011), and bilateral lung involvement (p=0.049) were higher in IMAs than in LPAs. IMAs had more advanced T, M, and Tumor, Node, and Metastasis stages than in LPAs (p=0.048, p=0.049, and p=0.022, respectively). There was no statistically significant difference in maximum standardized uptake value (SUV_max) between the IMA and LPA (p=0.078). The SUV was significantly lower in the nodular group than in the mass/pneumonic-type group (p=0.0001). A total of 11 patients died, of whom SUV_max values were significantly higher in these patients (p=0.031). Male gender (p=0.0001), rate of stage III-IV (p=0.0001), T3-T4 (p=0.021), M1 stages (p=0.0001), multifocality (p=0.0001), and bilateral lung involvement (p=0.0001) were higher in non-survivor.

Conclusions: Although CT images were useful for the differential diagnosis of LPAs and IMAs, SUV_max was not helpful for differentiation of these 2 groups. However, both ¹⁸F-FDG uptake and CT findings may play an important role in predicting prognosis in these patients.