D38 - Prediction of tumor response after neoadjuvant chemoradiotherapy in rectal cancer using 18fluorine-2-deoxy-d-glucose positron emission tomography-computed tomography: a prospective study

Abstract

Background: treatment of locally advanced rectal cancer (RC) includes pre-operative radiation therapy with chemotherapy (CRT) followed by radical surgery. The aim of this study was evaluate the role of 18fluorine-2-deoxy-D-glucose POSITRON EMISSION THOMOGRAPHY/COMPUTED TOMOGRAFY ( (18/F-FDG PET/CT) in the prediction of pathologic complete response (pCR) after CRT for rectal cancer. Material and methods: thirty-six patients (pts) ( 21 males and 15 females, age 33-84) with cT2-4 N0-2 rectal adenocarcinoma were included. This patients underwent integrated 18/F-FDG PET/CT, followed by neoadjuvant chemo-radiotherapy, PET/CT and surgery. The PET/CT results were compared with histopathological data ( Mandar's Tumor Regression Grade: TRG1 vs TRG5 as well as ypT0 N0 vs ypT1-4 N0-2. The patients were stratified according to the percentage decrease of standardized uptake values (SUV) of PET/TC: < 50% decrease, > 50% decrease and no metabolic activity. Results: All of 36 patients with PET/TC imaging before and after adjuvant chemoradiation was available. In 38 % of pts the post -CRT SUV was negative: 6 pts with pCR and TRG 1; 1 pt refused surgery; 1 pt developed liver metastasis. In 28 % of pts the post -CRT SUV decrease was > 50%: 2 pts with pCR and TRG 1, 1 pt developed lung metastasis. In 34 % of pts the post -CRT SUV decrease was < 50%: 2 pts with pCR and TRG 1, 2 pt developed lung metastasis, 1 pt developed liver metastasis and 1 pt developed brain metastasis. Conclusions: In rectal cancer PET/CT is a promising imaging marker to predict pRC to neoadjuvant theraphy.