PV QA 1 - Poster Viewing Q&A 1
Purpose/Objective(s):The best way to assess the response to chemoradiotherapy (CRT) in locally advanced esophageal carcinoma (LAEC) is not known. Interim 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT has been evaluated with promising results after completion of CRT in patients with LAEC. We used PET/CT to evaluate the metabolic response early during CRT and tried to correlate this response to overall survival. The hypothesis was SUVmax decrease during CRT was associated with better overall survival (OS).
Materials/Methods:Patients with biopsy-proven esophageal carcinoma underwent FDG PET/CT with evaluation of the standardized uptake value (SUV) before any treatment (SUV1) and during CRT after 20 Gy (SUV2). Metabolic response was defined as 1−(SUV2/SUV1). Surgery was discussed after 40 Gy. Results of interim PET were not considered for the therapeutic decision.
Results:One hundred sixteen patients (Male= 66.4%, Median age= 63; Adenocarcinoma (ADK)= 70%) met inclusion criteria. Forty-two patients (36.2%) were operated after neoadjuvant CRT. Median OS was 21.4 months with 1- and 3-year OS of 69 and 22% respectively. Median disease free survival (DFS) was 14 months with 1- and 3-year DFS of 53 and 16% respectively. Mean SUV at baseline was 13.6 (range 1–47) and 6.5 (0–20) at interim evaluation. There was a significant positive correlation between interim metabolic response and OS for the three predefined cut-offs values of SUVmax decrease. The 3-year OS of good responders, for a threshold SUVmax decrease of respectively 30%, 50% and 70%, were 31%, 40.8% and 45.3% as compared to 21%, 17% and 22% for poor metabolic responders (p=0.04, p=0.005 and p=0.01 respectively). The best cut-off value in terms of sensitivity and specificity was 50%. In multivariate analysis metabolic response using the 50% cut-off (p=0.001; IC95%(0.28–0.73)), surgery (p=0.007; IC95% (0.26–0.81)) and T stage (p=0.023; IC95% (1.09–3.49)) were significantly associated to OS. When separating the 116 patients in two groups, considering their primitive tumor histology, OS was significantly associated to metabolic response for both ADK (p=0.01) and Squamous Cell Carcinomas (p=0.03) using the 50% cut-off. We didn’t find any difference in OS whether both PET/CT were performed in the same or different institutions in case of metabolic response with a cut-off value of 50% (p=0.76 and p=0.6 respectively).In patients operated, using a Pearson chi square test, metabolic and histological complete responses were correlated using the 70% cut-off (p=0.048). When pooling patients with complete and major histological responses, these results were even more significant (p=0.023).
Conclusion:Metabolic response using SUVmax decrease at interim 18F-FDG PET/CT is associated with better survival and histological complete response, in patients treated by CRT for LAEC. This approach could help physician in assessing tumour response and prognosis particularly in patients treated by exclusive CRT.
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