Simple template-based optimization for pediatric total lymphoid irradiation (TLI) radiotherapy treatments

Area of Science:

• Radiation Oncology
• Pediatric Hematology/Oncology
• Medical Physics

Background:

• Total lymphoid irradiation (TLI) is a critical component in managing pediatric allogeneic hematopoietic stem cell transplantation (HSCT).
• Current TLI treatment planning can be complex and time-consuming.
• Optimizing dose delivery while minimizing toxicity is paramount in pediatric HSCT.

Purpose of the Study:

• To develop and evaluate a simplified treatment planning template for TLI using Volumetric Modulated Arc Therapy (VMAT).
• To assess the dosimetric quality of VMAT-based TLI plans compared to 3D-Conventional Radiotherapy (3D-CRT).
• To determine the feasibility of using a VMAT template for routine clinical application in pediatric HSCT.

Main Methods:

• A VMAT planning template was designed incorporating specific cost functions for the planning target volume (PTV) and organs at risk (OARs).
• Fifteen pediatric patients undergoing HSCT were planned using the VMAT template (8 Gy in 4 fractions).
• Dosimetric parameters including conformity index (CI), homogeneity index (HI), conformation number (CN), gradient index (GI), integral dose, and OAR doses were evaluated and compared to 3D-CRT plans.

Main Results:

• The VMAT template achieved excellent PTV coverage (V100% > 95%) with good dose conformation (mean CI = 1.33) and homogeneity (mean HI = 0.13).
• VMAT plans demonstrated superior conformation and comparable homogeneity to 3D-CRT.
• VMAT significantly reduced doses to most OARs compared to 3D-CRT, with minor exceptions like the right kidney.

Conclusions:

• The proposed VMAT template effectively simplifies TLI treatment planning for pediatric HSCT.
• This VMAT approach provides high-quality plans with improved OAR sparing compared to 3D-CRT.
• The template allows for minor modifications to further reduce doses to critical organs such as the heart and kidneys.