Impact of suboptimal dosimetric coverage of pretherapeutic 18F-FDG PET/CT hotspots on outcome in patients with locally advanced cervical cancer treated with chemoradiotherapy followed by brachytherapy

Abstract

Introduction: Areas of high uptake on pre-treatment 18 F-fluorodeoxyglucose (18 F-FDG) positron emission tomography/computed tomography (PET/CT), denoted as ''hotspots", have been identified as preferential sites of local relapse in locally advanced cervical cancer (LACC). The purpose of this study was to analyze the dosimetric coverage of these hotspots with high dose-rate brachytherapy (BT). Methods: For each patient, a rigid registration of the CT from the pre-treatment PET/CT with the radiotherapy planning CT was performed using 3D Slicer TM , followed by a manual volume correction by translation and deformation if necessary. The fuzzy locally adaptive Bayesian (FLAB) algorithm was applied to PET images to simultaneously define an overall tumour volume and the high-uptake sub-volume V1. The inclusion of V1 in the high-risk clinical target volume (CTV HR) and its dosimetric coverage were evaluated using 3D Slicer TM. The average of the 3-4 BT sessions was reported. Results: Forty-two patients with recurrence after chemoradiotherapy (CRT) for LACC were matched to 42 patients without recurrence. Mean ± standard deviation follow-up was 26 ± 11 months. In the recurrence group, V1 was not included in the CTV HR and not covered by the 85 Gy isodose in 17/42 patients (41%) (1/20 with pelvic recurrence and 16/22 with distant recurrence) and not by the 80 Gy isodose in 7/42 patients (17%) (all with distant recurrence). In the non-recurrence group, V1 was not included in CTV HR and not covered by the 85 Gy isodose in 3 patients only (7%). The hotspots coverage by the 85 Gy isodose was significantly better in patients who did not recur, but only when compared to patients with distant relapse (p < 0.0001). Conclusion: Suboptimal dosimetric coverage of high FDG uptakes on pretherapeutic PET could be associated with an increased risk of recurrence.

High-Dose-Rate Three-Dimensional Image-Guided Adaptive Brachytherapy (3D IGABT) for Locally Advanced Cervical Cancer (LACC): A Narrative Review on Imaging Modality and Clinical Evidence

“…Furthermore, a great number of studies have also concentrated on the predictive value of PET, and found that pretreatment values or relative changes in PET parameters [69], such as SUVmax and metabolic tumor volume (MTV), were associated with treatment responses and long-term outcomes [70]. Lucia et al found that the high-uptake volume on baseline PET/CT was correlated with the site of recurrence, and suboptimal dosage coverage of the area could be associated with a higher risk of recurrence [71,72]. The investigation of the dose-effect relationship within these PET-based biological target volumes remains a crucial area of research.…”