In the radiotherapeutic treatment of lung cancer, the dose that can be safely applied to the tumour is limited by the risk of radiation induced lung damage. This damage is characterized by parenchymal damage and vascular damage. In rats, we have found that radiation-induced vascular damage results in increased pulmonary artery pressure. Interestingly, the consequent loss of pulmonary function could be fully explained by this increase in pulmonary artery pressure. We hypothesize that also in patients a radiation induced increase in pulmonary artery pressure can be observed after radiotherapy, which may contribute to the development of radiation pneumonitis.

The objective is to test the hypothesis that radiotherapy for lung cancer induces an increase in pulmonary artery pressure.

Inclusion Criteria:

• Age ≥ 18 years
• WHO PS 0-2
• Histological or cytological confirmation of non-small cell lung cancer or an 18F-FDG-positive, growing mass on CT-thorax suggestive of NSCLC.
• Stage IIIA or IIIB
• Patients with extensive mediastinal lymph node involvement (such as N3), or large primary tumour size
• Adequate pulmonary function estimated by flow volume curves
• Life expectancy of at least 6 months
• Absence of any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol; those conditions should be discussed with the patient before registration in the trial.
• Planned for 25 x 2.4 Gy, with concomitant chemotherapy
• Before patient registration, written informed consent will be obtained.

Exclusion Criteria:

• Presence of contra-indications for undergoing MRI

Patient with stage III NSCLC