Early Metabolic Change after Induction Chemotherapy Predicts Histologic Response and Prognosis in Patients with Esophageal Cancer: Secondary Analysis of a Randomized Trial

Background Early metabolic response after preoperative induction chemotherapy (IC) appears to predict histologic response and prognosis in esophageal cancer (EC), but the usefulness of this approach needs further development. Objective We evaluated metabolic response after one cycle of IC using positron emission tomography (PET) to correlate PET response and outcomes. Patients and Methods We retrospectively analyzed PET data from a randomized phase 2 trial (NCT00525915) of chemoradiation and surgery with or without IC for the treatment of EC. PET was performed at baseline, after one cycle of IC, and 5–7 weeks after chemoradiation. The relationship between PET response (≥35% reduction in standardized uptake value [SUV]) after IC and treatment response was analyzed. Results In 63 patients who received IC, the mean initial SUV max prior to treatment was 11.9 ± 8.04 and mean SUV max after one cycle of IC was 6.47 ± 4.45. The mean SUV reduction after IC was 39.3%. Eleven of 37 PET responders achieved a pathologic complete response (pCR), but only two of 22 PET non-responders did (univariate logistic regression; odds ratio: 4.25, 95% confidence interval: 0.83–21.77; p = 0.08). PET responders to IC had significantly longer overall survival (OS) than PET nonresponders (log-rank p = 0.009). PET response after chemoradiation was not correlated with OS (log-rank p = 0.15). Conclusion Early PET response after IC is prognostic, but subsequent PET changes (for example, after chemoradiation) are not prognostic. Early PET response might have the potential of predicting pCR.