Stereotactic radiosurgery for gynecologic cancer

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Stereotactic body radiotherapy (SBRT) involves precise, high-dose radiation delivery in 1-3 treatments for tumors refractory to conventional therapies.
• SBRT necessitates advanced techniques for patient immobilization and respiratory motion management to minimize risks.

Purpose of the Study:

• To highlight the critical aspects of SBRT, including immobilization, motion control, and treatment planning.
• To discuss the associated risks of normal tissue injury and geographic miss and strategies to address them.

Main Methods:

• Rigid patient immobilization using custom casts, bean bags, or body-fix molds with abdominal compression.
• Intrafraction motion control via breath-hold techniques, active breathing coordination, or image-guided tracking of fiducials.
• Advanced imaging, including respiration-correlated CT and (18)F-FDG PET/CT, for precise target localization and margin definition.

Main Results:

• Submillimeter accuracy in radiation delivery is achievable through motion tracking, reducing planning target volumes.
• SBRT dose distributions exhibit high target coverage but decreased dose uniformity, impacting tumor control and normal tissue tolerance.
• A 0.5 cm clinical target volume expansion to the planning target volume improves target control without increasing normal tissue injury.

Conclusions:

• Effective SBRT requires meticulous immobilization and high-precision delivery to manage risks.
• Optimizing target margins and incorporating advanced imaging like PET/CT can further reduce geographic miss and improve outcomes.
• Ongoing research aims to identify new imaging biomarkers for enhanced SBRT planning, particularly for gynecologic cancers.