Use of Baseline 18F-FDG PET/CT to Identify Initial Sub-Volumes with Local Failure after Concomitant Chemoradiotherapy in Locally Advanced Cervical Cancer

Abstract

Locally advanced cervical cancer (CC) treated by chemoradiotherapy (CRT) have a significant local recurrence rate. The purpose of this study was to compare the initial high-uptake sub-volume (V1) on baseline18F-FDG PET/CT scans with the metabolic relapse (V2) sites after CRT in locally advanced CC. 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) performed before treatment and at relapse in 21 patients diagnosed with LACC and treated with CRT were retrospectively reviewed. CT images at the time of recurrence were registered to baseline CT using the 3D Slicer TM Expert Automated Registration module. The corresponding PET images were then registered using the same shift parameters. The fuzzy locally adaptive Bayesian (FLAB) algorithm was applied using 3 classes (one for background and the other two for tumor) in PET1 to simultaneously define an overall tumor volume and V1. In PET2, FLAB was applied using the standard 2-class version (one for background, one for tumor) in order to define V2. Four indices were used to determine the overlap of V1 and V2 (DICE, overlap fraction, X (X= V1∩V2)/V1) and Y(Y= V1∩V2)/V2)). The mean follow-up ±SD was 26±11 months. The overlap between V1 and V2 were good with an overlap fraction ranging from 0.62-0.81 (0.72±0.05), 0.73-1.00(0.91±0.24), 0.51-1.00 (0.79±0.29), 0.50-1.00 (0.75±0.13), for DICE, overlap fraction, X and Y, respectively. In our study, the overlap between the initial high-uptake sub-volume and the recurrent metabolic tumor sub-volume showed a good concordance. Despite these results need to be investigated in a larger cohort using a more standardized patient repositioning protocol for sequential PET imaging, there are encouraging for potential RT dose escalation in the future.