Inter-Breath-Hold Geometric and Dosimetric Variations in Organs at Risk during Pancreatic Stereotactic Body...

Area of Science:

• Radiation Oncology
• Medical Physics
• Oncology

Background:

• Pancreatic cancer has a low survival rate, making effective radiation therapy (RT) crucial.
• Deep Inspiration Breath Hold (DIBH) is used in RT to manage anatomical variations and reduce organ at risk (OAR) toxicities.
• The reproducibility and variability of DIBH in pancreatic cancer patients remain understudied.

Purpose of the Study:

• To systematically analyze anatomical reproducibility across multiple DIBH scans in pancreatic cancer patients undergoing RT.
• To evaluate the impact of anatomical variations on RT plan applicability and dosimetry.
• To highlight the necessity of adaptive RT strategies for pancreatic cancer treatment.

Main Methods:

• Systematic analysis of anatomical reproducibility using data from 20 pancreatic cancer patients.
• Four DIBH scans were acquired per patient, enabling the design of 80 stereotactic body radiation therapy (SBRT) plans.
• Comparison of OAR geometry, dose, and treatment delivery dosimetry across multiple DIBH scans.

Main Results:

• Significant variations in OAR geometry and dose were observed between same-subject DIBH scans.
• RT plans designed for one DIBH scan were not directly applicable to other scans from the same patient.
• Dosimetry during DIBH treatment delivery differed from that predicted by DIBH simulation CT scans.

Conclusions:

• Anatomical variations between DIBH scans necessitate adaptive RT approaches for pancreatic cancer.
• Adaptive RT techniques, such as those utilizing MR-Linacs, can account for inter-scan anatomical changes.
• Implementing ART can mitigate OAR toxicities caused by anatomical variations during pancreatic RT delivery.