Role of 18F-PET-CT to Predict Pathological Response After Neoadjuvant Treatment of Rectal Cancer

Objectives: Neoadjuvant radiochemotherapy (nCRT) is universally considered to be a valid treatment to achieve downstaging, improve local disease control and obtain better resectability in locally advanced rectal cancer (LARC). The aim of this study is to correlate the change in tumor 18 F -FDG PET-CT standardized uptake value (SUV) before and after nCRT, in order to obtain an early prediction of pathologic response (pR) achieved in patients with LARC. Data description: We performed a retrospective analysis of patients with LARC diagnosis who underwent curative resection. All patients received nCRT and surgical treatment was carried after 8/12 th . All patients underwent a baseline 18 F -FDG PET-CT scan within the week prior to the initiation of the treatment (PET-CT SUV1) and a second scan (PET-C T SUV2) within six weeks of the completion of nCRT. Furthermore, we evaluated the prognostic value of 18 F -FDG PET-CT in terms of disease free survival (DFS) and overall survival (OS) in patients with LARC.A total of 133 patients with LARC were included in the study. Patients were divided in two groups according to the TRG (tumor regression grade): 107 (80%) as Responders group (TRG0-TRG1) and 26 (25%) as the No-Responders group (TRG2-TRG3). We obtained a significant difference in Δ%SUV between the two different groups responders vs no responders (p<0.012).The results of this analysis have shown that 18F-FDG PET-CT may be an indicator in order to evaluate the pR to nCRT in patients with LARC. The decrease in 18F-FDG PET-CT uptake in the primary tumor may offer primary information in order to early identify those patients more likely to obtain a pCR to nCRT and predict those unlikely to regress significantly.