Types of deviation and review criteria in pretreatment central quality control of tumor bed boost in medulloblastoma\u2014an analysis of the German Radiotherapy Quality Control Panel in the SIOP PNET5 MB trial

Stefan Dietzsch,Albrecht Glück,Nicolas U Gerber,Beate Timmermann,Martin Benesch,Martin Mynarek,M Pazos ,Damien Charles Weber ,Denise Obrecht,Ralf Kitzing,Christiane Matuschek,Julia Remmele,V Lewitzki ,Semi Harrabi ,Tina Schlender,Kristin Gurtner,Clemens Seidel,Silke Frick,Rudolf Schwarz,Karolina Jabłońska ,Annett Braesigk,Stefan Rutkowski,Karin Dieckmann,Dirk Geismar,Rolf‐Dieter Kortmann

doi:10.1007/s00066-021-01822-0

Abstract

PurposeIn Germany, Austria, and Switzerland, pretreatment radiotherapy quality control (RT-QC) for tumor bed boost (TB) in non-metastatic medulloblastoma (MB) was not mandatory but was recommended for patients enrolled in the SIOP PNET5 MB trial between 2014 and 2018. This individual case review (ICR) analysis aimed to evaluate types of deviations in the initial plan proposals and develop uniform review criteria for TB boost.Patients and methodsA total of 78 patients were registered in this trial, of whom a subgroup of 65 patients were available for evaluation of the TB treatment plans. Dose uniformity was evaluated according to the definitions of the protocol. Additional RT-QC criteria for standardized review of target contours were elaborated and data evaluated accordingly.ResultsOf 65 initial TB plan proposals, 27 (41.5%) revealed deviations of target volume delineation. Deviations according to the dose uniformity criteria were present in 14 (21.5%) TB plans. In 25 (38.5%) cases a modification of the RT plan was recommended. Rejection of the TB plans was rather related to unacceptable target volume delineation than to insufficient dose uniformity.ConclusionIn this analysis of pretreatment RT-QC, protocol deviations were present in a high proportion of initial TB plan proposals. These findings emphasize the importance of pretreatment RT-QC in clinical trials for MB. Based on these data, a proposal for RT-QC criteria for tumor bed boost in non-metastatic MB was developed.

Highlights

Postoperative craniospinal irradiation (CSI) with boost delivery is a cornerstone of treatment of medulloblastomas (MB) [1]
In this analysis of pretreatment radiotherapy quality control (RT-QC), protocol deviations were present in a high proportion of initial tumor bed (TB) plan proposals
The International Society of Pediatric Oncology Peripheral Primitive Neuroectodermal Tumor 5 MB trial (SIOP PNET5 MB, ClinicalTrials.gov identifier: NCT02066220) included a TB boost with a reduced clinical target volume (CTV) margin of 1.0 cm compared to previously published trials [6, 11, 12]

Summary

Introduction

Postoperative craniospinal irradiation (CSI) with boost delivery is a cornerstone of treatment of medulloblastomas (MB) [1]. In standard-risk patients, the boost volume has changed from the posterior fossa (PF) to the tumor bed (TB) [2]. For PF boost, retrospective reports showed that inadequate treatment volumes were applied in a substantial proportion of patients [3,4,5]. A retrospective analysis of the French Medulloblastome-Société Française d’Oncologie Pédiatrique 1998 (M-SFOP 98) trial revealed adequate target volume and dose distribution of tumor bed boost [6]. The International Society of Pediatric Oncology Peripheral Primitive Neuroectodermal Tumor 5 MB trial (SIOP PNET5 MB, ClinicalTrials.gov identifier: NCT02066220) included a TB boost with a reduced clinical target volume (CTV) margin of 1.0 cm compared to previously published trials [6, 11, 12]. Protocol-compliant application of the TB boost was required to draw conclusions on the CTV margin out of the relapse patterns inside the posterior fossa. The pattern of relapse will be a subject of the final analysis of the protocol

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Results

Discussion

Conclusion