A 18FDG PET/CT-based volume parameter is a predictor of overall survival in patients with local advanced gastric cancer

Preoperative assessment and prognostic prediction of gastric cancer patients with peritoneal metastasis using 18F-FDG PET/CT before conversion surgery

BACKGROUND

Conversion therapy followed by conversion surgery (CS) can improve the prognosis of gastric cancer (GC) patients with peritoneal metastasis (PM). However, patients benefit differently. There is no way to confirm the prognostic benefit non-invasively and early. This retrospective study assessed the value of 18F-FDG PET/CT after conversion therapy in preoperative assessment and prognostic prediction of GC patients with PM.

RESULTS

Fifty-one GC patients with PM were enrolled. 18F-FDG PET/CT after conversion therapy helped in preoperative assessment. Its diagnostic accuracy for residual peritoneal lesions was slightly better than contrast-enhanced CT (72.5% vs. 61.2%, P = 0.229), although the difference was not statistically significant. TBR of peritoneal lesions could help preoperative assessment, with TBR of peritoneal lesions to the mediastinal blood pool SUVmax (TBRAmaxp) as the best predictor (cutoff = 0.705, specificity 80%, sensitivity 80%, AUC 0.825, P < 0.001). Additionally, PET/CT could predict prognosis and assess surgical benefit. SUVmax of peritoneal lesions (SUVmaxp) was the best predictor of 24 months survival (cutoff = 1.466, AUC 0.870, P = 0.002, Specificity 77.8%, Sensitivity 83.3%) and metabolic parameters of peritoneal lesions could predict OS and the prognosis of patients who underwent CS.

CONCLUSION

18F-FDG PET/CT provides quantitative imaging indicators for preoperative evaluation and prognostic prediction in GC patients with PM.

PET/CT for Predicting Occult Lymph Node Metastasis in Gastric Cancer

A portion of gastric cancer patients with negative lymph node metastasis at an early stage eventually die from tumor recurrence or advanced metastasis. Occult lymph node metastasis (OLNM] is a potential risk factor for the recurrence and metastasis in these patients, and it is highly important for clinical prognosis. Positron emission tomography (PET)/computed tomography (CT) is used to assess lymph node metastasis in gastric cancer due to its advantages in anatomical and functional imaging and non-invasive nature. Among the major metabolic parameters of PET, the maximum standardized uptake value (SUVmax) is commonly used for examining lymph node status. However, SUVmax is susceptible to interference by a variety of factors. In recent years, the exploration of new PET metabolic parameters, new PET imaging agents and radiomics, has become an active research topic. This paper aims to explore the feasibility and predict the effectiveness of using PET/CT to detect OLNM. The current landscape and future trends of primary metabolic parameters and new imaging agents of PET are reviewed. For gastric cancer patients, the possibility to detect OLNM non-invasively will help guide surgeons to choose the appropriate lymph node dissection area, thereby reducing unnecessary dissections and providing more reasonable, personalized and comprehensive treatments.

18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography Metabolic Parameters Before and After Neoadjuvant Chemotherapy Can Predict the Postoperative Prognosis of Locally Advanced Gastric Cancer

Objective: To explore the value of 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) metabolic parameters before and after neoadjuvant chemotherapy in predicting histopathological response and prognosis of locally advanced gastric cancer. Materials and Methods: A total of 56 patients with locally advanced gastric cancer underwent 18F-FDG PET/CT before and after neoadjuvant chemotherapy. The maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the lesions were measured before and after neoadjuvant chemotherapy. The percentage changes in the maximum standardized uptake value (ΔSUVmax%), mean standardized uptake value (ΔSUVmean%), metabolic tumor volume (ΔMTV%), and total lesion glycolysis (ΔTLG%), which were derived from 18F-FDG PET/CT, were calculated, and the cutoff values were determined by receiver operating characteristic curve analysis. Differences in progression-free survival (PFS) and overall survival (OS) between groups dichotomized by these cutoffs were analyzed using the Kaplan-Meier method and Cox proportional hazards regression model. Results: The patients were divided into histopathological responders and nonresponders according to the following cutoff values: 58.8% SUVmax reduction, 45.8% SUVmean reduction, 36.9% MTV reduction, and 57.8% TLG reduction. The differences in PFS and OS between groups dichotomized by these cutoffs were significant (all p < 0.01). Multivariate analysis suggested that a ΔTLG% > 57.8% was an independent postoperative risk factor for PFS (hazard ratio [HR] 0.348, 95% confidence interval [CI] 0.131-0.926, p = 0.035) and OS (HR 0.107, 95% CI 0.023-0.498, p = 0.004). Conclusions: The metabolic parameters before and after neoadjuvant chemotherapy of 18F-FDG PET/CT accurately reflected the chemotherapy effect, and ΔTLG% was the only independent postoperative predictive factor of PFS and OS for locally advanced gastric cancer.