Evaluating the Toxicity Reduction With Computed Tomographic Ventilation Functional Avoidance Radiation Therapy.

Area of Science:

• Radiation Oncology
• Medical Imaging
• Pulmonary Medicine

Background:

• Computed tomographic (CT) ventilation imaging is an emerging technique utilizing 4-dimensional (4D) CT data to assess lung ventilation.
• Previous research has indicated dose reductions to functional lung tissue, but the direct translation to decreased pulmonary toxicity has not been established.

Purpose of the Study:

• To estimate the reduction in pulmonary toxicity probability using CT ventilation-based functional avoidance planning.
• To quantify the dosimetric improvements and their impact on normal tissue complication probability (NTCP) models for pneumonitis.

Main Methods:

• Utilized 4D CT imaging from 70 lung cancer patients to generate CT ventilation maps.
• Developed NTCP models for grade 2+ and 3+ pneumonitis using maximum likelihood methods based on dose to functional lung.
• Generated functional avoidance plans for 30 patients, aiming to reduce dose to functional lung while adhering to RTOG 0617 constraints, and applied NTCP models to assess toxicity reduction.

Main Results:

• Functional avoidance planning achieved absolute NTCP reductions for grade 2+ pneumonitis of 6.3% (fV20 Gy), 7.8% (fV30 Gy), and 4.8% (mean dose).
• Absolute NTCP reductions for grade 3+ pneumonitis were 3.6% (fV20 Gy), 4.8% (fV30 Gy), and 2.4% (mean dose).
• Individual patients experienced maximum absolute reductions of 52.3% for grade 2+ and 16.4% for grade 3+ pneumonitis.

Conclusions:

• CT ventilation-based functional avoidance planning can significantly reduce the probability of radiation-induced pneumonitis.
• The study provides crucial data on the potential toxicity benefits of integrating CT ventilation into thoracic radiation therapy planning.
• Achieved average reductions of 7.1% for grade 2+ and 4.7% for grade 3+ pneumonitis, with substantial individual patient benefits.