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-EibrinkChristian Rübe, Geert O. Janssens

*Corresponding author for this work

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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 (GTVpre/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 (TVref) were established by three experienced radiation oncologists. The Dice Similarity Coefficient between the reference and participants (DSCref/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 CTVref was regarded as an unacceptable variation. Results: A total of 57/60 delineation sets were completed. The median DSCref/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 GTVpre, GTVpost, CTV-T and CTV-N, respectively. An unacceptable variation from the CTVref 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.

Original languageEnglish
Pages (from-to)39-47
Number of pages9
JournalClinical and translational radiation oncology
Volume28
DOIs
Publication statusPublished - May 2021

Keywords

  • Flank target volume
  • Highly-conformal radiotherapy
  • Inter-clinician variation
  • Pediatric renal tumors
  • Quality assurance
  • Wilms tumor

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