Online adaptive dose restoration in intensity modulated proton therapy of lung cancer to account for inter-fractional density changes

•An online adaptive workflow based on automatic dose restoration was implemented.•Restoration aims at compensating density changes by reproducing the planned dose.•Our tool mitigates the impact of inter-fractional density changes in proton therapy.•The need of comprehensive offline adaptation is reduced by introducing restoration.•Dose restoration improves target coverage and robustness respect to no adaptation.