One-year post-operative evaluation of stomach cancer using FDG PET/CT in patients with low suspicion of recurrence

1497 Objectives The purpose of this study was to see the clinical need of 1-year post-operative FDG-PET/CT in stomach cancer patients. Methods From June 2011 to June 2012, we retrospectively collected 95 consecutive stomach cancer patients who had curative surgical resection (Early gastric cancer (EGC) (n=46), Advanced gastric cancer (AGC) (n=49)). Patients were referred to 1-year post-operative FDG PET/CT without suspicion of recurrence (mean interval between operation and PET/CT: 12.7±0.8 months). FDG-PET/CT along with concurrent tumor markers (CA 72-4, CA 19-9 and CEA), abdomen CT and endoscopy were altogether used for reference of standard. Detection rates of local recurrence or metastasis of FDG-PET/CT were investigated. Results There was no local tumor recurrence in patients enrolled. Hypermetabolic activities on anastomosis site were in 67 cases (70.5%) which were all false positive. As for metastasis, 6 out of 95 cases proved to have metastasis. Twelve patients of AGC had abnormal hypermetabolic lesion suggesting metastases and half were proved as true-positive. Of these, 4 out of 6 cases had elevated serum CA 72-4 (253, 9.5, 5.9. 4.2 vs. 3.5, 3.0 U/mL). CA 72-4 levels of false positive case were 2.7, 2.9, 3.2, 3.3, 3.6 and 6.4 U/mL. None of the EGC patients showed increased FDG uptake suggesting metastasis. In addition, FDG-PET detected 3 cases of metachronous cancer in colon, lung and kidney, incidentally. Conclusions FDG PET/CT detected all recurrences in gastric cancer patients even with low suspicion of recurrence. Serum CA 72-4 level might be helpful in differentiating true lesions from false positives in FDG PET with low suspicion of recurrence of gastric cancer. However, routine one-year post-operative FDG-PET/CT in these setting is questionable, considering the low incidence of local recurrence or metastasis, especially in early gastric cancer.