Esophageal motion during radiotherapy: quantification and margin implications.

Area of Science:

• Radiation Oncology
• Medical Imaging
• Gastrointestinal Oncology

Background:

• Accurate radiation targeting is crucial for esophageal cancer treatment.
• Understanding organ motion is essential for effective radiotherapy planning.

Purpose of the Study:

• To quantify interfraction and intrafraction esophageal motion in right-left (RL) and anterior-posterior (AP) directions.
• To establish appropriate margins for internal target volume (ITV) in esophageal cancer radiotherapy.

Main Methods:

• Computed tomography (CT) simulation and CT-on-rails imaging were used in eight esophageal cancer patients.
• Interfraction and intrafraction displacements were measured using bone registries fused to the carina.
• Esophageal motion was analyzed in RL and AP directions, above and below the carina.

Main Results:

• The incidence of interfraction motion >= 5 mm was 24%, and intrafraction motion >= 5 mm was 13%.
• Average absolute motion was 4.2 mm or less in both RL and AP directions.
• Maximum motion occurred in the RL direction above the carina.

Conclusions:

• A 12 mm left, 8 mm right, 10 mm posterior, and 9 mm anterior margin is proposed for ITV.
• These findings can guide margin selection for intensity-modulated radiation therapy (IMRT) to account for organ motion and setup errors.