Utility of [18f]FDG Positron Emission Tomography for Predicting Histopathologic Response in Esophageal Carcinoma Following Chemoradiation

Abstract

For patients with esophageal cancer undergoing neoadjuvant chemoradiation (CRT) and surgery, complete histopathologic response (pCR) is associated with favorable overall survival (OS). The aim of this study was to evaluate the correlation between FDG-PET response to neoadjuvant CRT and pCR and OS. We evaluated patients with non-metastatic esophageal cancer treated with neoadjuvant CRT and resection from January 2007 through June 2012 at the Mayo Clinic. All patients underwent FDG-PET imaging prior to and after neoadjuvant CRT. Maximum standardized uptake values (SUVmax) and standardized uptake ratio (SUR) were measured pre- and post-CRT. SUR values were normalized to liver (SUR-L) and mediastinal blood pool (SUR-BP). FDG-PET complete response defined as metabolic activity normalization to hepatic and blood pool activity. Correlation between FDG-PET parameters and pCR was examined using logistic regression analyses. OS was estimated using the Kaplan-Meier method. A total of 193 patients (35 females, 158 males) with a median age of 62 years (range, 34-88) were followed for a median of 3.6 years after initiation of CRT. Most tumors were adenocarcinoma (85%) and staged as T3 (75%). Complete FDG-PET response and pCR occurred in 27% and 34% of patients, respectively. Histology, chemotherapy type, tumor stage and radiation dose were not significantly associated with FDG-PET response. Rates of pCR in patients with and without FDG-PET complete response were 42% and 31%, respectively (P = 0.17). The PPV and NPV of FDG-PET complete response in predicting pCR were 41.5% and 69.1%, respectively. No predictive correlation was found between change in SUVmax (ΔSUVmax) (P = 0.25, HR [95% CI] = 1.02 [0.99-1.06]), ΔSUR-BP (P = 0.20, HR [95% CI] = 1.05[0.97-1.12], or ΔSUR-L (P = 0.15, HR [95% CI] = 1.07[0.98-1.17]) and pCR. No threshold value of change in SUVmax correlated with pCR. 5-yr OS was 46% [CI: 28-65%] for patients with a complete FDG-PET response, compared to 44% [CI: 34-54] in patients without complete response (P = 0.78, HR = 0.93, 95% CI: 0.56-1.49). 5-yr OS in patients who achieved a pCR was 49% [CI 34-64%], compared to 43% [CI 33-53%] in those with residual tumor (P = 0.04, HR = 0.62, 95% CI: 0.38-0.97). For patients with esophageal cancer who received neoadjuvant CRT, pre- and post- treatment FDG-PET parameters did not correlate with pCR or OS. For patients with esophageal cancer undergoing neoadjuvant chemoradiation (CRT) and surgery, complete histopathologic response (pCR) is associated with favorable overall survival (OS).