Phase I will be designed as a longitudinal analysis, commencing at the time of diagnosis, tracking the progression of cachexia and associated dysmetabolic state, incorporating inflammatory profiles, energy metabolism (oxidative phosphorylation and glycolysis) and gut hormones, throughout treatment for OC and examining the impact of this decline on measures of physical functioning. Assessments will be completed at diagnosis (T0), cycle 2 chemotherapy (T1), cycle 3 chemotherapy (T2), pre-oesophagectomy (T3), post-oesophagectomy (T4), 4-weeks post-surgery (T5) and six months post-surgery (T6). All assessments will be completed during the same day as routine out-patient appointments thereby reducing the burden on participants. Furthermore, blood samples will be taken during routine clinical sampling and CT scans will be completed as part of routine medical care.