This study evaluated the role of (18)F-FDG PET as an early predictor of histopathologic response to neoadjuvant chemoradiotherapy and overall survival in patients with adenocarcinoma of the esophagus undergoing multimodal therapy.
Methods: Thirty-seven patients with locally advanced adenocarcinoma of the esophagus underwent pretreatment and an intratreatment (18)F-FDG PET scan in the second week of a 6-wk regimen of neoadjuvant chemoradiotherapy. Histopathologic response and overall survival were correlated with percentage change in (18)F-FDG uptake (%Δmaximum standardized uptake value [%ΔSUVmax]).
Results: In 16 patients (43%), treatment induced a histopathologic response (<10% viable tumor cells), which was associated with a significant (P < 0.05) survival benefit. The optimal reduction in (18)F-FDG uptake, which separated histopathologic responders and nonresponders, was a -26.4% ΔSUVmax (receiver-operating-characteristic curve analysis). At this separation, sensitivity, specificity, positive predictive value, negative predictive value, and accuracy (area under the receiver operating characteristic curve) were 62.5%, 71.4%, 62.5%, 71.4%, and 67.4%, respectively, for intratreatment (18)F-FDG PET scans. Kaplan-Meier survival analysis of (18)F-FDG PET responders (>26.4% reduction in SUVmax), compared with (18)F-FDG PET nonresponders (<26.4% reduction in SUVmax), revealed no survival benefit for responders (P = 0.6812).
Conclusion: The %ΔSUVmax during the second week of induction chemoradiation did not correlate either with histopathologic response or with survival. Our results show that, in contrast to published reports on neoadjuvant chemotherapy, combined chemoradiotherapy in patients with adenocarcinoma of the esophagus lowers the predictive accuracy of early repeated (18)F-FDG PET in identifying histopathologic responders and those with chances for increased survival below clinically applicable levels.