Locoregional control in high-risk neuroblastoma using highly-conformal image-guided radiotherapy, with reduced margins and a boost dose for residual lesions.

Introduction: Radiotherapy protocols for high-risk neuroblastoma (HR-NBL) vary across international studies. The purpose of this study was to evaluate the locoregional control in a national HR-NBL cohort treated with highly-conformal image-guided radiotherapy (IGRT), using reduced margins, and a boost dose for residual lesions.
Materials and Methods: Patients treated with radiotherapy as part of first-line HR-NBL treatment between 2015 and 2022 were eligible. To obtain clinical, internal, and planning target volumes, +0.5 cm, 4DCT-based, and + 0.3/0.5 cm margins, respectively, were added to the edited gross tumour volumes. Prescription dose was 21.6/1.8 Gy, followed by 14.4/1.8 Gy for any residual lesions measuring ≥ 1 cm ³ at the time of radiotherapy planning. Intensity-modulated arc therapy was combined with daily cone beam CT-based online patient position verification. Locoregional failure (LRF) rates were compared for the presence of residual lesions < 1 cm ³ vs. ≥ 1 cm ³ (with/without locoregional activity on nuclear- and MRI[diffusion-weighted imaging]-scans) pre-radiotherapy, age at diagnosis, MYCN-status, [ ¹³¹ I]mIBG therapy, response to induction chemotherapy, interval to radiotherapy onset, and metastatic site irradiation.
Results: Among the 77 included patients, 34 had residual lesions (median volume: 10.0 cm ³ , IQR 4.8-29.9) with activity visible on 17 nuclear- and 10 MRI-scans. Five-year LRF rate was 7.8 % (95 % confidence interval 1.8-13.8), and not significantly different between those with residual lesions < 1 cm ³ vs. ≥ 1 cm ³ (6.4 % vs. 14.3 %, respectively, p = 0.27), or any of the other variables. All 6 LRFs (2 isolated, 4 combined) occurred < 1.5 years post-radiotherapy.
Conclusion: In HR-NBL, IGRT with reduced margins and a boost dose for residual lesions ≥ 1 cm ³ demonstrated excellent locoregional control, comparable to modern literature.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Atia Samim, Annemieke S. Littooij, Max Peters, Bart de Keizer, Alida F.W. van der Steeg, Raquel Dávila Fajardo, Kathelijne C.J.M. Kraal, Miranda P. Dierselhuis, Natasha K.A. van Eijkelenburg, Martine van Grotel, Roel Polak, Cornelis P. van de Ven, Marc H.W.A. Wijnen, Enrica Seravalli, Mirjam E. Willemsen-Bosman, Max M. van Noesel, Godelieve A.M. Tytgat, Geert O. Janssens: No conflict of interest].
(Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)