Functional lung avoidance proton radiation therapy planning using anatomy-wise computed tomography-derived lung ventilation imaging

This study aimed to assess the dosimetric benefits of functional avoidance proton therapy planning using anatomy-wise computed tomography (CT)-derived lung ventilation imaging (VIaw), which helps spare both high-functioning lung volume (HFV) and recoverable low-functioning lung volume (rLFV) for the first time in proton therapy. In a cohort of 18 lung cancer patients, VIaw was generated from planning CT scans. For each patient, we created anatomical and functional-guided intensity-modulated radiation therapy (aIMRT, fIMRT) and proton therapy (aIMPT, fIMPT) plans. For a subset of eight patients with tracheal obstruction by the tumor, we generated two extra rLFV-sparing plans (rfIMRT, rfIMPT) that specifically incorporated constraints to spare both HFV and rLFV. For the 18 patients, functional IMPT (fIMPT) demonstrated superior HFV sparing, achieving statistically significant reductions in all HFV dose parameters compared to fIMRT (V5: 34.9%±18.1%; V20: 20.6%±17.0%; V30: 9.6%±17.4%; mean dose: 25.3%±10.5%; all p < 0.05) and additional significant sparing compared to aIMPT. For the eight patients with tracheal obstruction by the tumor, rfIMPT significantly reduced rLFV dose compared to fIMPT (V20: 11.4%±6.2%; V30: 16.4%±5.9%; mean dose: 13.0%±4.7%; all p < 0.05) and showed advantages over rfIMRT, particularly in V5 reduction (4.5%±5.4%, p < 0.05). IMPT plans consistently outperformed IMRT in OAR sparing, reducing contralateral lung mean dose to approximately one-fourth of IMRT levels. Other dosimetric parameters for rfIMPT and fIMPT were comparable and within acceptable limits. Incorporating VIaw into functional proton planning effectively enhanced dose sparing of HFV and rLFV while maintaining excellent OAR protection. This approach demonstrates the potential of proton therapy to simultaneously preserve functional lung regions and facilitate recovery of compromised areas. Not applicable.