Esophagus sparing with IMRT in lung tumor irradiation: an EUD-based optimization technique

Area of Science:

• Radiation Oncology
• Medical Physics
• Clinical Oncology

Background:

• Lung tumors often overlap with the esophagus, posing a challenge for radiation dose escalation.
• Optimizing radiation therapy requires balancing tumor coverage with organ-at-risk sparing.

Purpose of the Study:

• To evaluate generalized equivalent uniform dose (gEUD) for optimizing dose escalation in lung tumors overlapping the planning target volume (PTV).
• To assess the benefit of escalating dose in the PTV portion not overlapping the esophagus.

Main Methods:

• Intensity modulated radiation therapy (IMRT) plans were optimized using various cost functions, including mean dose (MD) and gEUD.
• gEUD was applied to the whole PTV and to the PTV excluding the esophagus.
• Plans were evaluated for PTV coverage (absence of cold spots) and overall gEUD.

Main Results:

• Mean dose (MD) optimized plans resulted in cold spots in approximately 5% of the PTV.
• gEUD optimization for the whole PTV increased doses while respecting normal tissue constraints.
• Simultaneous gEUD optimization for the whole PTV and the PTV minus the esophagus yielded the best results, avoiding cold spots under aggressive tumor assumptions.

Conclusions:

• gEUD-based IMRT optimization increases PTV dose in lung tumors overlapping the esophagus.
• This method maintains minimum dose coverage while allowing for dose escalation.
• Simultaneous optimization of the whole PTV and the PTV minus the esophagus is a promising strategy.