Prognostic Value of FDG-PET/CT Parameters in Patients with Locally Advanced Rectal Cancer Treated with Neoadjuvant Approach
Fatma SERT1,Aylin ORAL2,Recep SAVAŞ3,Deniz YALMAN1,Serdar ÖZKÖK1
1Department of Radiation Oncology, Ege University, Faculty of Medicine, İzmir-Turkey
2Department of Nuclear Medicine, Ege University, Faculty of Medicine, İzmir-Turkey
3Department of Radiology, Ege University, Faculty of Medicine, İzmir-Turkey
DOI : 10.5505/tjo.2019.2164 OBJECTIVE
To determine the prognostic and/or predictive role of 18F-FDG PET/CT parameters, such as SUVmax, SUVmean, Metabolic Tumor Volume (MTV) and Total Lesion Glycolysis (TLG=MTVxSUVmean), for the patients with locally advanced rectal cancer (LARC) treated with neoadjuvant radiotherapy±chemotherapy.

Between January 2005 and December 2016, a total of 106 patients with clinical T3-4 and/or N+ rectal cancer without distant metastasis were included in this study. Correlation between metabolic and volumetric parameters and tumor characteristics was evaluated. Prognostic factors for overall survival (OS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS) were analyzed.

The median follow-up duration for all patients was 39.0 months (range, 6?103 months). Pathologic complete response (pCR) was defined as the absence of viable cancer cells in the resected specimen (ypT0N0). pCR was achieved in 17% of all cases (18/106). There was a weak correlation between SUVmax of primary tumor and MTV ([r]=0.238; p<0.001). However, SUVmax of primary tumor and TLG were significantly correlated (r=0.538; p<0.001). Neither SUVmax nor SUVmean was affected by patient and tumor characteristics. Posttreatment extensive stage of disease (p=0.013), absence of concomitant CT (p=0.012), MTV ≥14.65 cm3 (p=0.008), and TLG ?117.00 (p=0.023) were unfavorable prognostic factors for OS on multivariate analysis.

Although FDG-PET is not a standard imaging modality for the treatment of rectal cancers, a negative effect of high MTV and TLG on OS was shown in our study. We should consider more intense treatment approaches for tumors with high MTV and TLG values. Keywords : FDG-PET/CT; locally advanced rectal cancer; prognostic factors; radiochemotherapy