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A simplified CT-based definition of the lymph node levels in the node negative neck
O B Wijers1, P C Levendag, T Tan
1Department of Radiation Oncology, University Hospital Rotterdam/Daniel den Hoed Cancer Center, The Netherlands.
Summary
A simplified protocol for 3D conformal radiotherapy (CRT) elective neck irradiation (ENI) effectively controls disease while preserving salivary glands. This method reduces contouring time, making conformal ENI more practical for clinical use.
Area of Science:
- Radiation Oncology
- Medical Imaging
- Head and Neck Cancer Treatment
Background:
- Three dimensional (3D) conformal radiotherapy (CRT) for elective neck irradiation (ENI) aims to improve local disease control.
- Minimizing xerostomia by excluding major salivary glands from treatment portals is a key objective in ENI.
- Standardization of CT-based target volumes for the clinically negative neck is essential for 3DCRT implementation.
Purpose of the Study:
- To modify an existing CT-based protocol for neck target volume delineation into a more practical and simplified version.
- To enable rapid contouring and facilitate the routine clinical implementation of conformal ENI.
- To assess the feasibility of a simplified protocol for achieving conformal ENI while sparing major salivary glands.
Main Methods:
- Re-evaluation of an 'original' CT-based definition for elective neck node regions (2-5) using 15 planning CT scans.
- Simplification of contouring guidelines by reducing anatomical landmarks and utilizing CT slice interpolation.
- Evaluation of target coverage and salivary gland sparing using both 'original' and 'simplified' protocols via DVH analysis in a supraglottic laryngeal carcinoma case.
Main Results:
- The 'original' and 'simplified' 3D elective neck target delineation protocols showed good agreement and reproducibility in BEV projections.
- Dose-volume histogram (DVH) analysis revealed no significant differences in target coverage or parotid gland sparing between the two protocols.
- The simplified protocol demonstrated comparable target coverage and salivary gland sparing to the original protocol.
Conclusions:
- The simplified protocol for 3D elective neck target delineation provides comparable target coverage and effective sparing of major salivary glands.
- Integration with an interpolation program significantly reduces contouring time, enhancing the practicality of the simplified protocol.
- The simplified protocol makes elective neck irradiation with major salivary gland sparing an achievable goal in routine clinical practice.