[18F]-fluorodeoxyglucose-positron emission tomography for the assessment of histopathologic response and prognosis after completion of neoadjuvant chemotherapy in gastric cancer.

BACKGROUND AND OBJECTIVES: Neoadjuvant chemotherapy is applied to improve the prognosis of patients with advanced gastric cancer. However, only a major histopathological response will provide a benefit. Recent studies suggest that [(18)F]-fluorodeoxyglucose-positron-emission-tomography (FDG-PET) correlates with response and survival in patients with gastroesophageal adenocarcinomas undergoing neoadjuvant chemotherapy. We evaluated the potential of FDG-PET for the assessment of response and prognosis in the multimodality treatment of gastric cancer.

METHODS: Study patients were recruited from a prospective observation trial. Forty two patients with advanced gastric cancer received neoadjuvant chemotherapy and subsequently 40 patients underwent standardized gastrectomy (2 patients with tumor progression had therapy limited to palliative chemotherapy without surgery). Histomorphologic regression was defined as major response when resected specimens contained <10% vital tumor cells. FDG-PET was performed before and 2 weeks after the end of neoadjuvant chemotherapy with assessment of the intratumoral FDG-uptake [pre-treatment standardized uptake value (SUV1); post-treatment SUV (SUV2); percentage change (SUVDelta%)].

RESULTS: Histomorphological tumor regression was confirmed as a prognostic factor (P = 0.039). No significant correlations between SUV1, SUV2, or SUVDelta% and response or prognosis were found.

CONCLUSION: FDG-PET seems not to be an imaging system that effectively characterizes major/minor response and survival in patients with gastric cancer following multimodality treatment.