A reduced liver ¹⁸F-FDG uptake may be related to hypoalbuminemia in patients with malnutrition

Objective: ¹⁸F-FDG PET/CT is a hybrid imaging method widely used as a useful, noninvasive imaging modality for evaluating various neoplastic diseases. When assessing the tumor uptake, the liver and the mediastinal blood pool are often used as a reference region. In daily clinical practice, the ¹⁸F-FDG uptake in the liver sometimes appears to decrease on PET images of patients with malnutrition. The purpose of this study was to investigate whether or not the liver ¹⁸F-FDG uptake is decreased in patients with malnutrition. Methods: We retrospectively analyzed 246 patients who underwent ¹⁸F-FDG PET/CT from January 2018 to June 2018 and whose blood serum albumin was measured within 1 month of PET/CT. We compared the liver uptake and mediastinal blood uptake of patients with low serum albumin level (< 4.0 g/dl) and hypoalbuminemia (< 3.5 g/dl) with those with a normal serum albumin level (≥ 4.0 g/dl). Correlations between the liver and mediastinal blood uptake and the serum albumin level were also calculated. Results: The maximum standardized uptake value (SUV_max) and mean standardized uptake value (SUV_mean) of the liver in 117 patients with low serum albumin were 3.1 ± 0.5 and 2.3 ± 0.3, respectively, while they were 2.9 ± 0.4, 2.0 ± 0.3 in 29 patients with hypoalbuminemia; these values were all significantly lower than the respective ones (3.4 ± 0.5, 2.5 ± 0.4) in 129 patients with normal serum albumin (all p < 0.001). The SUV_mean of the mediastinal blood uptake in patients with hypoalbuminemia and normal serum albumin were 1.6 ± 0.2 and 1.7 ± 0.3, respectively (p = 0.053). The serum albumin level demonstrated a significantly positive, moderate correlation with the liver SUV_mean, showing a regression line of y = 0.31x + 1.1 (r = 0.41, p < 0.001). Conclusion: The liver ¹⁸F-FDG uptake tended to decrease in patients with hypoalbuminemia. In the patients with malnutrition, the mediastinal blood pool may be a more stable reference than the liver for evaluating the tumor activity because hypoalbuminemia is considered to less strongly influence the mediastinal blood pool than that in the liver.