The Importance of Quasi-4D Path-Integrated Dose Accumulation for More Accurate Risk Estimation in Stereotactic Liver...

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Intrafraction organ motion significantly impacts radiation dose accuracy.
• Conventional 3D dose calculations may not adequately account for organ deformation during treatment.
• Accurate dose estimation is crucial for predicting normal tissue complication probabilities (NTCP) and stochastic risks.

Purpose of the Study:

• To demonstrate a quasi-4-dimensional (quasi-4D) method for improved risk estimation in radiotherapy.
• To compare dose calculations and risk predictions between conventional 3D and quasi-4D methods for liver stereotactic body radiotherapy (SBRT).
• To evaluate the impact of dose calculation method on NTCP and stochastic risks for radiation-induced carcinogenesis and cardiac complications.

Main Methods:

• Conventional 3D and quasi-4D dose calculations were performed using dose warping for dose accumulation.
• The study included patients with liver metastases undergoing SBRT (42 Gy in 6 fractions).
• NTCP and stochastic risks were evaluated for healthy peripheral structures, including cardiac organs and large bowel.

Main Results:

• Conventional 3D dose computation led to significant dose under- or overestimation for organs at risk (e.g., kidneys, large bowel, duodenum).
• Cardiac complication risks were underestimated by >20% with the 3D approach.
• Discrepancies in excess relative risk (ERR) ranged up to ~30%, with significant differences in radiocarcinogenesis risk prediction between 3D and 4D methods.

Conclusions:

• Quasi-4D dose calculation provides more accurate dose estimates compared to conventional 3D methods for liver SBRT.
• The 3D approach can lead to substantial inaccuracies in dose delivery and risk assessment.
• Improved dose estimation using quasi-4D methods is vital for understanding dose-response relationships in hypofractionated radiotherapy and optimizing patient outcomes.