The Value Of ¹⁸F-FDG PET/CT In Diagnosis And Treatment Of Gastric Cancer

PART ONE : A Prospective Evaluation of the Utility of ¹⁸F-FD G PET/CT in Staging of Gastric Cance rObjective To evaluate the value of pretreatment ¹⁸F-FDG PET/CT in staging of gastric cancer.Methods From January 2011 to June 2015, gastric cancer patients（21 males, 9 females; median age 63.5 years） proved by pathology were retrospectively studied. Median follow- up was 15.7 moths（rang 13-40months）. All patients were evaluated with ¹⁸F-FDG PET/CT before treatment. ¹⁸F-FDG PET/CT images were evaluated by two experienced observers blinded to the clinical data and histopathology results. For semi-quantitative analysis, the maximum standardized uptake value（SUV） was measured. FDG uptake was defined to be positive qualitatively when the SUVmax of a focal FDG uptake was higher than 2.5. Final confirmation of the primary tumour metastasis was established by follow-up C T scans in 6 months after treatment.Results According to pathological results, 13 patients were adenocarcinoma, whose degree of differentiation were not determined, 7 patients were classified as poorly differentiated, 3 patients were classified as moderately-poorly differentiated, 3 patients were classified as moderately differentiated, 3 patients were certified as signer ring cell, 1 patient was certified as endocrine carcinoma.（1）.Among these 30 patients, postive FDG uptake of primary tumors was observed in 29 patients（96.7%）. ¹⁸F-FDG PET/CT confirmed primary tumors in 4 patients.（2）.In 16 patients（53.3%）, local lymph nodes metastasis were confirmed:16 patients（100%） were identified by PET/CT and 9 patients（56.3%） were identified by CT. 8 patients were upstaged by PET/CT in N stage.（3）. distant metastasis were confirmed in 17 patients（56.7%）. There was one false-positive on PET/CT（FDG uptake in ascending colon and adrenal gland） and one false-negative on PET/CT（a omentum metastasis had no FDG uptake）. There were two lesions detected by PET/CT but not with CT（a pleural metastasis and a bone metastasis）, 4 patients were upstaged by PET/CT in M stage.Conclusions ¹⁸F-FDG PET/C T images of gastric cancer can detect primary tumors and identify metastasis accurately. ¹⁸F-FDG PET/CT is highly recommended for staing in gastric cancer patients before treatment.PART TWO: The Value of ¹⁸F-FD G PET/CT in Evaluating Che motherapeutic Response with Gastric CancerObjective To assess the value of ¹⁸F-FDG PET/CT in evaluating response to chemotherapy in patients with gastric cancer.Methods From January 2011 to June 2014, gastric cancer patients（17 males, 4 females; median age 59 years） proved by pathology were retrospectively studied. Median follow-up was 26.62 months（rang 2-50months）. All patients were evaluated with ¹⁸F-FDG PET/CT in the median course of chemotherapy. ¹⁸F-FDG PET/CT images were evaluated by two experienced observers blinded to the clinical data and histopathology results. For semi-quantitative analysis, the maximum standardized uptake value（SUV） was measured.Response to treatment was defined as 35% decrease in SUV or lesions disapperaed or no FDG uptake sites. Stable disease was defined as no changes in PET/CT compared to CT before chemotherapy. Progression was defined as new lesions in PET/CT compared to pretreatment C T.Results According to pathological results, 4 patients were adenocarcinoma, whose degree of differentiation was not determined. 9 patients were classified as poorly differentiated, 1 patients were classified as moderately-poorly differentiated, 4 patients were classified as moderately differentiated, 2 patients were certified as signer ring cell, 1 patient was certif ied as endocrine carcinoma. Among 21 patients with gastric cancer, postive FDG uptake of primary tumors was observed in 11 patients, local lymph nodes FDG uptake were observed in 9 patients, postive FDG uptake of organ metastasis was observed in 10 patients. 4 patients responsed to chemotherapy, 6 patients kept stable and 11 patients were progressed. Patients who responsed to chemotheraty or kept stable were treated with previous chemotherapy regimen. chemotherapy regimen were changed in 10 of the 11 progression disease patients.Conclusions¹⁸F-FDG PET/CT images of gastric cancer during chemotherapy can effectively evaluate response to chemotherapy, which may be useful to the clinical decision.PART THREE: The Role of ¹⁸F-FDG PET/CT in the Evaluation of Gastric Cancer RecurrenceObjective To investigate the diagnostic performance of postoperative ¹⁸F-FDG PET/CT as a surveillance modality for gastric cancer.Methods From January 2011 to June 2014, 49 gastric cancer patients（37 males, 12 females; median age 58 years） proved by pathology were retrospectively studied. Median follow-up was 37.7months（rang 13-61months）. All patients were evaluated with ¹⁸F-FDG PET/CT after treatment. ¹⁸F-FDG PET/C T images were evaluated by two experienced observers blinded to the clinical data and histopathology results. For semi-quantitative analysis, the maximum standardized uptake value（SUV） was measured. FDG uptake was defined to be positive qualitatively when the SUVmax of a focal FDG uptake was higher than 2.5. Final confirmation was determined by clinical follow-up using conventional CT scan with/without subsquent histopathologic diagnosis. The Kaplan-Meier method was used to determine factors associated with poor overall survival. P<0.05 was considered statistically significant.Results According to pathological results, 2 patients were adenocarcinoma, whose degree of differentiation was not determined, 22 patients were classified as poorly differentiated, 6 patients were classified as moderately-poorly differentiated, 13 patients were classified as moderately differentiated,1 patient was classified as well- moderately differentiated, 1patient was classified as well differentiated, 2 patients were certified as signer ring cell and 1 patient was certified as undifferentiated. Among 49 patients with gastric cancer, 30 patients developed recurrence, postive FDG uptake of primary tumors was observed in 14 patients, local lymph nodes FDG uptake were observed in 22 patients, postive FDG uptake of organ metastasis was observed in 20 patients. Regardless of the recurrence sites, the sensitivity, specificity, accuracy, positive predictive value and negative predictive value of PET/CT were 100%, 78.9%, 88.2%, 91.8% and 100%, respectively. FDG-PET-postive tumours were associated with an inferior overall survival（p=0.001）.Conclusions Our study showed ¹⁸F-FDG PET/CT was a accurate postoperative surveillance modality for detecting recurrence in gastric cancer.