Robust dose planning objectives for mesorectal radiotherapy of early stage rectal cancer - a multicentre dose planning study

Ane Appelt, Ellen Kerkhof, Lars Nyvang, Ernst Harderwijk, Natalie L. Abbott, Mark Teo, Femke P. Peters, Camilla J. S. Kronborg, Karen-Lise Garm Spindler, David Sebag-Montefiore, Corrie A. M. Marijnen, STAR-TREC Collaborative Group

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Abstract

Background and purpose: Organ preservation strategies are increasingly being explored for early rectal cancer. This requires revision of target volumes according to disease stage, as well as new guidelines for treatment planning. We conducted an international, multicentre dose planning study to develop robust planning objectives for modern radiotherapy of a novel mesorectal-only target volume, as implemented in the STAR-TReC trial (NCT02945566).
Materials and methods: The published literature was used to establish relevant dose levels for organ at risk (OAR) plan optimisation. Ten representative patients with early rectal cancer were identified. Treatment scans had mesorectal target volumes as well as bowel cavity, bladder and femoral heads outlined, and were circulated amongst the three participating institutions. Each institution produced plans for short course (SCRT, 5 × 5 Gy) and long course (LCRT, 25 × 2 Gy) treatment, using volumetric modulated arc therapy on different dose planning systems. Optimisation objectives for OARs were established by determining dose metric objectives achievable for ≥90% of plans.
Results: Sixty plans, all fulfilling target coverage criteria, were produced. The planning results and literature review suggested optimisation objectives for SCRT: V10Gy < 180 cm3, V18Gy < 110 cm3, V23Gy < 85 cm3 for bowel cavity; V21Gy < 15% and V25Gy < 5% for bladder; and V12.5Gy < 11% for femoral heads. Corresponding objectives for LCRT: V20Gy < 180 cm3, V30Gy < 130 cm3, V45Gy < 90 cm3 for bowel cavity; V35Gy < 22% and V50Gy < 7% for bladder; and V25Gy < 15% for femoral heads. Constraints were validated across all three institutions.
Conclusion: We utilized a multicentre planning study approach to develop robust planning objectives for mesorectal radiotherapy for early rectal cancer.
Original languageEnglish
Pages (from-to)14-21
JournalTechnical Innovations & Patient Support in Radiation Oncology
Volume11
DOIs
Publication statusPublished - Sep 2019

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