Increased evidence for the prognostic value of late-treatment FDG-PET uptake in non-tumor affected oesophagus in irradiated patients with oesophageal carcinomas

Purpose: 18F-fluorodeoxyglucose (FDG) uptake within irradiated non-tumor affected oesophagus (NTO) at re-staging positron emission tomography (PET) is a potential surrogate to measure radiation induced inflammation (RIF). RIF itself was shown to be of high prognostic relevance in patients undergoing preoperative radiochemotherapy (RCT) for locally advanced oesophageal cancer. We assessed the prognostic relevance of NTO uptake in an independent cohort of patients treated with definitive RCT.

Methods: Seventy-two patients with oesophageal squamous cell carcinomas treated with curative intent definitive RCT were retrospectively evaluated. All patients underwent pre-treatment and re-staging FDG-PET after 40-50 Gray radiation dose. Standardized uptake values (SUVmax/SUVmean), metabolic tumor volume (MTV) and relative changes between pre-treatment and re-staging PET (∆SUVmax/∆SUVmean) were determined within tumor and NTO. Univariate Cox regression with respect to overall survival (OS), local control (LC), distant metastases (DM) and treatment failure (TF) was performed. Independence of parameters was tested in multivariate Cox regression.

Results: ∆SUVmax NTO and MTV were prognostic factors for all investigated clinical endpoints (OS, LC, DM, TF). Inclusion of clinical and PET tumor parameters in multivariate analysis showed ∆SUVmax NTO as an independent prognostic factor. Furthermore, multivariate analysis of ∆SUVmax NTO with previously published cutoffs from the preoperatively treated patients revealed ∆SUVmax NTO as independent prognostic factor for OS (HR=1.88, p=0.038), TF (HR=2.11, p=0.048) and DM (HR=3.02, p=0.047).

Conclusions: NTO-related tracer uptake during course of treatment in patients suffering from esophageal carcinoma was proven to be of high prognostic relevance. Thus, metabolically activity of NTO measured by ∆SUVmax NTO is a potential candidate for future treatment individualization (i.e. organ preservation).