ESTRO technical guideline: intensity modulated radiotherapy and image guided radiotherapy for rectal cancer

INTRODUCTION: Intensity Modulated Radiotherapy (IMRT) and Image Guided Radiotherapy (IGRT) have become an integral part of standard care for rectal cancer, but evidence-based detailed guidance is lacking to support its clinical implementation and use. This European SocieTy for Radiotherapy and Oncology (ESTRO) technical guideline aimed to assess the available evidence and provide recommendations for their use in rectal cancer treatment.

MATERIALS AND METHODS: The ESTRO Lower Gastrointestinal (GI) Cancer guidelines subcommittee formed a writing panel to address key questions (KQs) on the application of IMRT and IGRT in rectal cancer management. The panel conducted a literature review and where evidence was insufficient, expert consensus was used.

RESULTS: The writing panel (2 RTTs, 2 medical physics experts, 3 radiation oncologists) identified 14 KQs. Recommendations were based on low to moderate evidence and/or expert consensus. Supine positioning is preferred for patient comfort and stability. Comfortable full bladder should be used. For OAR delineation and dose optimization, mandatory (Bladder, Bowel Cavity, Femoral Heads) and optional OAR were defined. Auto-delineation is supported for OAR and can be considered for target volumes. Dose metrics for minimizing gastrointestinal and genitourinary toxicity were identified. Auto-planning tools and MR-only workflows are feasible, both require proper QA. Uncertainties from setup and target volume shape variations must be accounted for with appropriately defined margins. Daily volumetric image guidance is recommended for treatment verification.

CONCLUSION: This ESTRO technical guideline for the use of IMRT and IGRT for rectal cancer was developed to support development and implementation into clinics.