Prospective study on the FDG–PET/CT predictive and prognostic values in patients treated with neoadjuvant chemoradiation therapy and radical surgery for locally advanced rectal cancer

2-[fluorine-18]fluoro-2-deoxy-D-glucose–positron emission tomography/computed tomography (FDG–PET/CT) was carried out before and after neoadjuvant chemoradiotherapy (NCRT) followed by radical surgery for locally advanced rectal cancer (LARC). The aim of this study was to define its predictive and prognostic values. Patients with cT3-T4 N-/+ carcinoma of medium/low rectum received daily 5-fluorouracil–based chemotherapy infusion and radiation therapy on 6-week period followed by surgery 7–8 weeks later. Tumour metabolic activity, expressed as maximum standardised uptake value (SUV-1 = at baseline and SUV-2 = pre-surgery), was calculated in the most active tumour site. Predictive and prognostic values of SUV-1, SUV-2 and Δ-SUV (percentage change of SUV-1 - SUV-2) were analysed towards pathological response (pR) in the surgical specimen and disease recurrence, respectively. Eighty consecutive patients entered the study. SUV-1, SUV-2 and Δ-SUV appeared singly correlated with pR, but not one of them resulted an independent predictive factor at multivariate analysis. After a median follow-up of 44 months, 13 patients (16.2%) presented local and/or distant recurrence. SUV-2 ≤5 was associated with lower incidence of disease recurrence and resulted prognostic factor at multivariate analysis. Dual-time FDG–PET/CT in patients with LARC treated with NCRT and radical surgery supplies limited predictive information. However, an optimal metabolic response appears associated with a favourable patient outcome.