Spectrum of gastric malignancy on 18F-FDG PET/CT: a pictorial essay

Prognostic value and clinical correlations of 18-fluorodeoxyglucose metabolism quantifiers in gastric cancer

AIM: To investigate the correlations of pre-treatment positron emission tomography-computer tomography (PET-CT) metabolic quantifiers with clinical data of unstratified gastric cancer (GC) patients.

METHODS: Forty PET-CT scans utilising 18-fluorodeoxyglucose in patients who received no prior treatment were analysed. Analysis involved measurements of maximum and mean standardised uptake volumes (SUV), coefficient of variation (COV), metabolic tumour volumes and total lesion glycolysis of different thresholds above which the tumor volumes were identified. The threshold values were: SUV absolute value of 2.5, 30% of SUVmax, 40% of SUVmax, and liver uptake-based (marked _2.5, ₃₀, ₄₀ and _liv, respectively). Clinical variables such as age, sex, clinical stage, performance index, weight loss, tumor histological type and grade, and CEA and CA19.9 levels were included in survival analysis. Patients received various treatment modalities appropriate to their disease stage and the outcome was defined by time to metastasis (TTM) and overall survival (OS). Clinical and metabolic parameters were evaluated by analysis of variance, receiver operating characteristics, univariate Kaplan-Meier, and multivariate Cox models. P < 0.05 was considered statistically significant.

RESULTS: Significant differences were observed between initially disseminated and non-disseminated patients in mean SUV (6.05 vs 4.13, P = 0.008), TLG_2.5 (802 cm³vs 226 cm³; P = 0.031), and TLG₃₀ (436 cm³vs 247 cm³, P = 0.018). Higher COV was associated with poor tumour differentiation (0.47 for G3 vs 0.28 for G1 and G2; P = 0.03). MTV_2.5 was positively correlated to patient weight loss (< 5%, 5%-10% and > 10%: 40.4 cm³vs 123.6 cm³vs 181.8 cm³, respectively, P = 0.003). In multivariate Cox analysis, TLG₃₀ was prognostic for OS (HR = 1.001, 95%CI: 1.0009-1.0017; P = 0.047) for the whole group of patients. In the same model yet only including patients without initial disease dissemination TLG₃₀ (HR = 1.009, 95%CI: 1.003-1.014; P = 0.004) and MTV_2.5 (HR = 1.02, 95%CI: 1.002-1.036; P = 0.025) were prognostic for OS; for TTM TLG₃₀ was the only significant prognostic variable (HR = 1.006, 95%CI: 1.001-1.012; P = 0.02).

CONCLUSION: PET-CT in GC may represent a valuable diagnostic and prognostic tool that requires further evaluation in highly standardised environments such as randomised clinical trials.

Less may be as good as more: feasible and effective method to differentiate gastric uptake solely on planar gallium scan in the era of SPECT/CT

We presented a patient with abnormal focal accumulation of 67Ga in the left upper abdomen. After drinking water, we successfully identified the abnormal radioactivity that was from the stomach. Subsequent endoscopic examination did not reveal gastric pathological condition. Gastric accumulation of 67Ga may relate to pathological conditions or physiological uptake, confounding interpretation of 67Ga scintigraphy. Simple water ingestion method can rapidly identify gastric 67Ga uptake, and the shape of distended stomach can also help to differentiate pathological conditions from physiological uptake, which is especially helpful for a busy nuclear medicine department and for places where the SPECT/CT systems are not available.