Small Bowel Dose Tolerance for Stereotactic Body Radiation Therapy

Area of Science:

• Radiation Oncology
• Gastrointestinal Oncology
• Medical Physics

Background:

• Published small bowel dose tolerance limits for stereotactic body radiation therapy (SBRT) lack consistency.
• Existing literature presents diverse and often conflicting data on SBRT dose limits for the small intestine.

Purpose of the Study:

• To organize and unify existing small bowel dose tolerance limits for SBRT.
• To develop a dose-volume histogram (DVH) Risk Map for small bowel SBRT.
• To assess the safety spectrum of gastrointestinal tract doses in SBRT using clinical data.

Main Methods:

• Organized published SBRT dose tolerance limits and integrated data from MD Anderson at Cooper.
• Constructed a DVH Risk Map to delineate low-risk and high-risk SBRT dose tolerance limits for the small bowel.
• Utilized probit dose-response models with clinical data from two institutions to estimate complication risks.

Main Results:

• Established a unified framework for small bowel SBRT dose tolerance limits, creating a DVH Risk Map.
• Identified 21Gy to 5cc in 3 fractions as a reasonably safe SBRT dose with a 6.5% estimated risk of grade 3+ complications.
• Demonstrated that 16.2Gy to 5cc in 3 fractions yields a lower estimated risk of 2.5%.
• All analyzed high-risk limits showed ≤8.2% risk, and low-risk limits had ≤4% risk.

Conclusions:

• The developed DVH Risk Map provides a unified understanding of small bowel dose tolerance in SBRT.
• Results support current clinical SBRT practices for the small bowel.
• The findings suggest potential for dose escalation in SBRT while maintaining acceptable toxicity profiles.