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

François Lucia; Vincent Bourbonne; Dorothy Gujral; Gurvan Dissaux; Omar Miranda; Maelle Mauguen; Olivier Pradier; Ronan Abgral; Ulrike Schick

doi:10.1016/j.ctro.2020.05.004

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

Clin Transl Radiat Oncol. 2020 May 11:23:50-59. doi: 10.1016/j.ctro.2020.05.004. eCollection 2020 Jul.

Authors

François Lucia¹, Vincent Bourbonne¹, Dorothy Gujral^{2

3}, Gurvan Dissaux¹, Omar Miranda¹, Maelle Mauguen¹, Olivier Pradier¹, Ronan Abgral⁴, Ulrike Schick¹

Affiliations

¹ Radiation Oncology Department, University Hospital, Brest, France.
² Clinical Oncology Department, Imperial College Healthcare NHS Trust, Charing Cross Hospital, Hammersmith, London, UK.
³ Department of Cancer and Surgery, Imperial College London, London, UK.
⁴ Nuclear Medicine Department, University Hospital, Brest, France.

Abstract

Introduction: Areas of high uptake on pre-treatment ¹⁸F-fluorodeoxyglucose (¹⁸F-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.

Keywords: Brachytherapy; Hotspot; Image-guided; PET/TDM; cervical cancer.