Functional lung avoidance in radiotherapy using optimisation of biologically effective dose with non-coplanar beam...

Area of Science:

• Radiation Oncology
• Medical Physics
• Pulmonary Medicine

Background:

• Minimizing radiation dose to functioning lung is crucial in non-small cell lung cancer (NSCLC) radiotherapy to reduce lung morbidity.
• External beam radiotherapy planning requires careful consideration of dose distribution within the lung parenchyma.

Purpose of the Study:

• To develop and evaluate a method for avoiding beam delivery through functional lung in NSCLC patients.
• To quantify the potential benefits of functional lung avoidance in reducing radiation-induced lung injury.

Main Methods:

• Retrospective analysis of 12 NSCLC patients treated with single photon emission computed tomography (SPECT) functional lung avoidance.
• Treatment planning involved weighting lung dose by functional image intensity and optimizing non-coplanar intensity-modulated beams.
• A logistic model was used to predict the reduction in pneumonitis risk.

Main Results:

• The volume of lung irradiated to a 5 Gy functionally weighted dose was significantly reduced (11.8% vs 20.9%, p=0.002).
• Mean functionally weighted lung dose was also reduced (4.1 Gy vs 4.5 Gy, p=0.002).
• Predicted pneumonitis risk decreased by an average of 4.3% (p=0.002).

Conclusions:

• Optimizing non-coplanar beam orientations effectively reduces dose/volume lung parameters by over 10% in NSCLC patients.
• This functional lung avoidance strategy consistently improves outcomes regardless of lung perfusion patterns.
• The developed method shows promise for improving radiation-associated lung injury outcomes.