NTCP models based on CT-guided online adaptive SBRT for abdominal lymph node oligometastases

Area of Science:

• Radiation Oncology
• Medical Physics
• Clinical Oncology

Background:

• Stereotactic body radiotherapy (SBRT) is used for oligometastases.
• Online adaptive radiotherapy (ART) allows for real-time treatment adjustments.
• Predicting toxicity is crucial for optimizing SBRT in abdominal and pelvic lymph node (A-P LN) treatments.

Purpose of the Study:

• To analyze the correlation between radiation dose and toxicity in CT-guided online adaptive SBRT for A-P LN oligometastases.
• To develop a Normal Tissue Complication Probability (NTCP) model for predicting acute gastrointestinal (GI) toxicity.
• To identify dose-volume histogram (DVH) parameters associated with GI toxicity.

Main Methods:

• Prospective analysis of patients undergoing SBRT for A-P LN oligometastases.
• Utilized 45 Gy in five fractions with three pre-treatment plans.
• Employed a decision tree for plan selection and extracted DVH parameters (Dmax, D0.2 cc, D0.5 cc, D1cc, D2cc, D5cc, D10cc) for NTCP modeling via logistic regression.

Main Results:

• 55 treatments in 52 patients were analyzed.
• No grade ≥3 acute or late GI toxicity observed; 36.4% experienced grade ≤2 acute GI toxicity.
• Significantly higher median doses to gastrointestinal organs (GIO) were found in patients with toxicity. The NTCP model predicted a 50% chance of grade ≤2 GI toxicity at D0.5 cc of 57 Gy EQD2.

Conclusions:

• Significant correlations were identified between GI dose parameters (D0.2 cc, D0.5 cc, D1cc, D2cc, D5cc) and acute grade ≤2 GI toxicity.
• The developed NTCP models can help reduce toxicity rates by guiding dose reduction strategies.
• This study provides valuable insights for optimizing SBRT planning to minimize GI toxicity in A-P LN treatments.