Prognostic value of 18F-FDG PET/CT metabolic tumor volume for complete pathologic response and clinical outcomes after neoadjuvant chemoradiation therapy for locally advanced esophageal cancer.

150 Background: The prognostic value of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) has not yet been defined in locally advanced esophageal cancer (LAEC). This study aims to elucidate the prognostic role of PET/CT for patients treated with neoadjuvant chemoradiation (CRT) followed by esophagectomy. Methods: We retrospectively evaluated patients with LAEC treated from 2006 to 2014 with neoadjuvant CRT followed by esophagectomy. 86 patients had pre-CRT and post CRT PET/CT scans performed at our institution. These scans were imported into an image analysis program. PET parameters maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), mean standardized uptake value (SUVmean), and peak standardized uptake value (SUVpeak) were recorded for both pre-CRT and post-CRT scans. MTV was defined using a previously described liver method. The correlation of these parameters with pathologic complete response (pCR) and clinical outcomes was analyzed using binomial logistic regression and cox regression. Results: Pre-CRT MTV < 33.6 (median value) was significantly predictive of pCR (p = 0.019, OR = 3.064). An ROC curve was produced to determine a binary cutoff of 35.8, yielding a higher specificity (62.3% vs. 59%) and the same sensitivity (72.7%), increasing the significance to p = 0.010, OR = 3.378. The ratio of postMTV/preMTV (MTVr) was calculated. MTVr > 0.2857 (median value) was significantly predictive of distant metastasis (DM) after esophagectomy (p = 0.018, OR = 3.680). An ROC curve was produced to determine a binary cutoff of 0.301, which increased specificity from 57.1% to 60.3%, and maintained the same sensitivity at 81.3%, increasing the significance to p = 0.014, OR = 3.815. SUVmax, mean and peak were not predictive. Conclusions: Pre CRT MTV was predictive of pCR and MTVr was predictive of DM. Our data suggests that MTV is superior to SUVmax, mean and peak in predicting for response to treatment in LAEC. Further study is needed to determine if Pre CRT MTV and change in MTV can help define which patients will most benefit from esophagectomy and/ or adjuvant chemotherapy.