Post-Treatment/Pre-operative PET Response Is Not an Independent Predictor of Outcomes for Patients With Gastric and GEJ Adenocarcinoma.

Abstract

To determine whether changes in positron emission tomography (PET) avidity correlated with histologic response and were independently associated with outcome. The implications of metabolic response to neoadjuvant therapy as measured by repeat PET imaging remain ill-defined for patients with gastric and gastroesophageal junction (GEJ) cancers. We identified patients with gastric and GEJ adenocarcinoma who were evaluated with PET imaging before and following neoadjuvant treatment, and subsequently underwent curative resections. Spearman rank correlation and Cox proportional hazards regression were used to evaluate standardized uptake value (SUV) and histologic response, pathologic parameters, and disease-specific survival (DSS). From 2002 to 2013, 192 patients met our inclusion criteria. The median SUVmax response was 57.3% (range: -110% to 100%) for patients with GEJ cancers, with a corresponding median pathologic treatment response of 80% (range: 0% to 100%). The median SUVmax response was 32.5% (-230% to 100%) for patients with gastric cancers, with a corresponding median pathologic treatment response of 35% (range: 0% to 100%). The Spearman correlation between SUVmax response and histologic response was significant for patients with GEJ (rho = 0.19, P = 0.04) and gastric (rho = 0.44, P < 0.0001) cancers. For patients with GEJ (P <0.0001 to 0.046) and gastric cancers (P = 0.0003 to 0.016), histopathologic response and tumor staging predicted DSS. SUVmax response failed to demonstrate a relationship with DSS when entered into multivariable models containing conventional pathologic variables. Following completion of neoadjuvant therapy for gastric and GEJ adenocarcinoma, histopathologic staging remains the best predictor of outcome. Repeat post-treatment/preoperative PET imaging for the purpose of prognostication is of limited value.