Dose-Volume Constraints Parameters for Lung Tissue in Thoracic Radiotherapy Following Immune Checkpoint Inhibitor...

Area of Science:

• Radiation Oncology
• Medical Physics
• Thoracic Oncology

Background:

• Immunotherapy preceding thoracic radiotherapy (ICI-TRT) is increasingly used for non-small-cell lung cancer (NSCLC).
• Symptomatic radiation pneumonitis (RP) is a significant concern in this patient population.
• Identifying risk factors and establishing safe dose constraints for RP is crucial for optimizing treatment outcomes.

Purpose of the Study:

• To identify risk factors associated with symptomatic radiation pneumonitis (RP, Grade ≥ 2) following immunotherapy preceding thoracic radiotherapy (ICI-TRT).
• To establish safe lung dose constraints for thoracic radiotherapy in patients treated with ICI-TRT.
• To compare derived dose thresholds with current guideline recommendations.

Main Methods:

• Retrospective analysis of 118 NSCLC patients who received ICI-TRT.
• Evaluation of clinical and lung dosimetric parameters, including mean lung dose (MLD) and lung volume receiving specific doses (V10, V20, V30, V40).
• Use of receiver operating characteristic (ROC) curves to determine optimal threshold values for dosimetric predictors of symptomatic RP.

Main Results:

• The incidence of symptomatic RP was 25.4%.
• Independent risk factors identified include tumor locations, immunotherapy-radiotherapy interval, MLD, V10, V20, V30, and V40.
• Optimal threshold values for MLD, V10, V20, V30, and V40 were found to be 9.7 Gy, 26.3%, 15.9%, 13.3%, and 8.6%, respectively, which are lower than current guidelines.

Conclusions:

• Recommended lung dose thresholds for MLD, V10, V20, V30, and V40 are lower than current guidelines.
• Radiotherapy planning should aim to maintain dosimetric parameters below these new thresholds to minimize symptomatic RP.
• Adherence to these lower thresholds may reduce the cumulative incidence of symptomatic RP to less than 12%.