The Diagnostic Performance of FDG PET/CT for Recurrent Gastric Cancer Is Significantly Affected by Primary Tumor FDG Uptake Level

Abstract

Introduction: The outcome of advanced gastric cancer remains poor, and early detection of recurrence is important. FDG PET/CT is known to be useful in detection of recurrent gastric cancer, but the specific indication for surveillance with PET/CT in gastric cancer following curative resection remains unclarified to date. In this study, we evaluated the relation between FDG uptake of primary tumor and the patterns of recurrent disease in advanced gastric cancer. And we investigated whether FDG-avid primary tumors are associated with improved performance of surveillance PET/CT for detecting recurrent gastric cancer. Methods: Subjects were 372 patients (mean age 57.3 ± 11.5 y, male 254) with advanced gastric cancer who underwent curative surgery. All subjects had FDG PET/CT for initial staging and for recurrence surveillance after surgery. Primary tumors were classified as FDG-avid if they displayed focal uptake with SUVmax ≥ 4, or were otherwise classified as non-FDG-avid. Follow up FDG PET/CT were evaluated for recurrence. The presence of recurrence was determined by medical records with > 11 mo of follow-up. Results: Of the 372 subjects, 240 had FDG-avid primary tumors (64.5%; 59.7 y, male 175), whereas 132 had non-FDG-avid primary tumors (35.5%; 52.9 y, male 79). During follow-up, 72 patients (19.6%) were diagnosed to have recurrence. Among 63 cases with eligible follow-up PET/CT, 42 (3 at anastomosis site only) had FDG-avid primary tumors and 21 (2 at anastomosis site only) had non-FDG-avid tumors. For all recurrences, PET/CT sensitivity was 34/42 (81.0%) for the FDG-avid group and 11/21 (52.4%) for the non-FDG-avid group (P = 0.018). For recurrences outside the anastomosis site, PET/CT sensitivity was 41/58 (70.7%) for all subjects, 32/39 (82.1%) for the FDG-avid group, and 9/19 (47.4%) for the non-FDG-avid group (P = 0.006). PET/CT specificity for recurrence was 97.3%, 97.1%, and 97.5% for respective groups (P = n.s.). Conclusion: The result of our study showed that the detection sensitivity of recurrent gastric cancer by FDG PET/CT was superior in patients with FDG avid primary tumors than patients with FDG non-avid tumors. Hence, follow-up FDG PET/CT appears to have greater value for recurrence surveillance in patients with high tumor FDG uptake on initial PET/CT.