PET Could Predict Response to Neoadjuvant Therapy and Long‐Term Survival of Patients with Esophageal Cancer

Abstract

Dear Editor, We have read with the great interest the article by Brown et al. [1] entitled ‘‘Accuracy of PET-CT in predicting survival in patients with esophageal cancer’’: They concluded that ‘‘This study does not support the use of SUVmax on pretreatment PET scans as a prognostic tool for patients with esophageal cancer, especially in those who have received neoadjuvant therapy.’’ However, we have several concerns about their conclusion. Many articles have already reported on the use of positron emission tomography (PET) in pretreatment evaluation of esophageal cancer, as was mentioned in the Brown et al. report [1]. Metabolic activity of carcinoma could be evaluated by measuring tumor glucose metabolism with the glucose analog [18F]fluorodeoxyglucose (FDG) [2]. There is accumulating evidence that supports the fact that the pathologic response after neoadjuvant therapy is the major determinant of long-term survival of patients with esophageal cancer. Patients treated with neoadjuvant therapy who achieve pathologic complete response (pCR) have a significantly higher rate of complete resection, fewer recurrences, and improved 5-year overall survival and disease-free survival [3]. However, in the Brown et al. report there was a lack of analysis on the pCR subgroup and no discussion about the relationship between the pretreatment standard uptake value (SUV) and the pathologic response. Furthermore, PET could predict the pathologic response by comparing the SUVs from before and after neoadjuvant therapy, not just the pretreatment SUV. Ott et al. [2] classified patients as metabolic responders when tumor metabolic activity had decreased by more than 35 % 2 weeks after the end of neoadjuvant therapy. Metabolic responders showed a high pathologic response rate (44 %), with a 3-year survival rate of 70 %, compared to metabolic nonresponders with a pathologic response rate of 5 % (P = 0.001) and a 3-year survival rate of 35 % (P = 0.01). Brucher et al. [4] analyzed pathologic responses after neoadjuvant therapy. In pathologic responders, the SUV decreased by 72 ± 11 %, while in pathologic nonresponders it decreased by only 42 ± 22 % (P \ 0.05), between pretreatment and 3 weeks after the end of neoadjuvant therapy. Nonresponders to PET scanning had a significantly worse survival rate after resection than responders. The data from Flamen et al. [5] further found that the agreement between the assessment of the change in tumor activity by PET preand post-neoadjuvant therapy and pathologic evaluation could achieve 78 %. Therefore, we believe that PET scanning could predict the response to neoadjuvant therapy and the long-term survival of the patients with esophageal cancer. It is feasible to predict the pathologic response of neoadjuvant therapy by assessing the SUV reduction ratio before and after treatment and thereby predict long-term survival. The SUV reduction ratio and the pathologic response, which have been ignored by authors, are two crucial factors