Inter-clinician delineation variation for a new highly-conformal flank target volume in children with renal tumors: A SIOP-Renal Tumor Study Group international multicenter exercise

Joeri Mul; Patrick Melchior; Enrica Seravalli; Daniel Saunders; Stephanie Bolle; Alison L Cameron; Kristin Gurtner; Semi Harrabi; Yasmin Lassen-Ramshad; Naomi Lavan; Henriette Magelssen; Henry Mandeville; Tom Boterberg; Petra S Kroon; Alexis N T J Kotte; Bianca A W Hoeben; Peter S N van Rossum; Martine van Grotel; Norbert Graf; Marry M van den Heuvel-Eibrink; Christian Rübe; Geert O Janssens

doi:10.1016/j.ctro.2021.03.001

Inter-clinician delineation variation for a new highly-conformal flank target volume in children with renal tumors: A SIOP-Renal Tumor Study Group international multicenter exercise

Clin Transl Radiat Oncol. 2021 Mar 11:28:39-47. doi: 10.1016/j.ctro.2021.03.001. eCollection 2021 May.

Authors

Joeri Mul^{1

2}, Patrick Melchior³, Enrica Seravalli², Daniel Saunders⁴, Stephanie Bolle⁵, Alison L Cameron⁶, Kristin Gurtner⁷, Semi Harrabi⁸, Yasmin Lassen-Ramshad⁹, Naomi Lavan¹⁰, Henriette Magelssen¹¹, Henry Mandeville¹², Tom Boterberg¹³, Petra S Kroon², Alexis N T J Kotte², Bianca A W Hoeben^{1

2}, Peter S N van Rossum², Martine van Grotel¹, Norbert Graf¹⁴, Marry M van den Heuvel-Eibrink¹, Christian Rübe³, Geert O Janssens^{1

2}

Affiliations

¹ Princess Máxima Center for Pediatric Oncology, Utrecht, the Netherlands.
² Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, the Netherlands.
³ Dept. of Radiation Oncology, Saarland University Hospital, Homburg, Germany.
⁴ Dept. of Clinical Oncology, The Christie Hospital, Manchester, United Kingdom.
⁵ Dept. of Radiation Oncology, Gustave Roussy, Villejuif, France.
⁶ Bristol Cancer Institute, University Hospitals, Bristol, United Kingdom.
⁷ Dept. of Radiation Oncology, University Hospital Carl Gustav Carus, Dresden, Germany.
⁸ Dept. of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany.
⁹ Dept. of Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark.
¹⁰ St. Luke's Radiation Oncology Network, Dublin, Ireland.
¹¹ Dept. of Oncology, Oslo University Hospital, Oslo, Norway.
¹² Dept. of Clinical Oncology, The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom.
¹³ Dept. of Radiation Oncology, Ghent University Hospital, Ghent, Belgium.
¹⁴ Dept. of Pediatric Oncology, Saarland University Hospital, Homburg, Germany.

Abstract

Background and purpose: Recently, the SIOP-RTSG developed a highly-conformal flank target volume definition for children with renal tumors. The aims of this study were to evaluate the inter-clinician delineation variation of this new target volume definition in an international multicenter setting and to explore the necessity of quality assurance.

Materials and methods: Six pediatric renal cancer cases were transferred to ten radiation oncologists from seven European countries ('participants'). These participants delineated the pre- and postoperative Gross Tumor Volume (GTV_pre/post), and Clinical Target Volume (CTV) during two test phases (case 1-2 and 3-4), followed by guideline refinement and a quality assurance phase (case 5-6). Reference target volumes (TV_ref) were established by three experienced radiation oncologists. The Dice Similarity Coefficient between the reference and participants (DSC_ref/part) was calculated per case. Delineations of case 5-6 were graded by four independent reviewers as 'per protocol' (0-4 mm), 'minor deviation' (5-9 mm) or 'major deviation' (≥10 mm) from the delineation guideline using 18 standardized criteria. Also, a major deviation resulting in underestimation of the CTV_ref was regarded as an unacceptable variation.

Results: A total of 57/60 delineation sets were completed. The median DSC_ref/part for the CTV was 0.55 without improvement after sequential cases (case 3-4 vs. case 5-6: p = 0.15). For case 5-6, a major deviation was found for 5/18, 12/17, 18/18 and 4/9 collected delineations of the GTV_pre, GTV_post, CTV-T and CTV-N, respectively. An unacceptable variation from the CTV_ref was found for 7/9 participants for case 5 and 6/9 participants for case 6.

Conclusion: This international multicenter delineation exercise demonstrates that the new consensus for highly-conformal postoperative flank target volume delineation leads to geometrical variation among participants. Moreover, standardized review showed an unacceptable delineation variation in the majority of the participants. These findings strongly suggest the need for additional training and centralized pre-treatment review when this target volume delineation approach is implemented on a larger scale.

Keywords: AA, abdominal aorta; AP/PA, Anterior-Posterior/Posterior-Anterior; CT, Computed Tomography; CTV-N, Clinical Target Volume of the lymph node area; CTV-T, Clinical Target Volume of the primary Tumor; DICOM, Digital Imaging and Communications in Medicine; DSC, Dice Similarity Coefficient; Flank target volume; GTVpre/post, pre- and postoperative Gross Tumor Volume respectively; HR, High-Risk; Highly-conformal radiotherapy; IGRT, Image-Guided Radiotherapy; IMRT, Intensity-Modulated Radiotherapy; IR, Intermediate-Risk; IVC, inferior vena cava; Inter-clinician variation; MRI, Magnetic Resonance Imaging; OAR, organs at risk; Pediatric renal tumors; Quality assurance; RT, radiotherapy; RTOG, Radiation Oncology Group; RTSG, Renal Tumor Study Group; SIOP, International Society for Pediatric Oncology; TVintersect, intersect target volume; TVref, reference target volumes; WT, Wilms’ tumor; Wilms tumor; n.a., not applicable; part, participant; ref, reference.