SU-E-T-246: Preliminary Normal Tissue Complication Probability (NTCP) Analysis for Radiation Pneumonitis (RP) after...

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Stereotactic Body Radiation Therapy (SBRT) is increasingly used for large and central lung tumors.
• Determining dose tolerance limits for radiation-induced pneumonitis (RP) is crucial for safe SBRT delivery.

Purpose of the Study:

• To analyze Normal Tissue Complication Probability (NTCP) using the Lyman model to establish dose tolerance limits for RP in hypofractionated SBRT.
• To identify dosimetric predictors of RP in patients treated with SBRT for large lung tumors.

Main Methods:

• Volumetric Modulated Arc Therapy (RapidArc) data from 18 patients with lung tumors >80cc were analyzed.
• Toxicity was scored using Common Toxicity Criteria AE4.0, with a median follow-up of 12.8 months.
• Lyman model NTCP analysis was performed on various dose-volume histogram (DVH) parameters, including total lung V5Gy and contralateral lung V5Gy.

Main Results:

• Radiation-induced pneumonitis (RP) occurred in 5 patients (3 Grade 2, 2 Grade 3).
• Total lung V5Gy and contralateral lung V5Gy were identified as the strongest predictors of RP (p < 0.0001).
• A 10% risk of Grade 2-3 RP corresponded to a total lung V5Gy of 28.4% and a contralateral lung V5Gy of 21.6%.

Conclusions:

• Total lung V5Gy and contralateral lung V5Gy are key predictors of RP following RapidArc SBRT for large lung tumors.
• These findings provide initial dose tolerance limits but require validation in larger cohorts with longer follow-up.
• The study utilized DVH analysis software developed by Dr. Grimm.