Our group has shown in a modeling study that increasing the radiation dose to pre-specified normal tissue dose constrains could lead to increased TCP with the same NTCP. In a subsequent phase I trial, the investigators showed the safety of this approach. Here, the investigators want to investigate its efficacy in a prospective study in patients with stage I-III NSCLC, who are selected for radical radiotherapy

Eligible patients (see below) will receive radiotherapy to the primary tumor and the initially involved mediastinal lymph nodes to the following MLD (Mean Lung Dose):

• MLD=19 Gy when Fev1 and DLCO > 50% of the predicted value
• MLD=15 Gy when Fev1 and/or DLCO 40-49% of the predicted value
• MLD=10 Gy when Fev1 and/or DLCO <40% of the predicted value

Other dose-constrains: spinal cord max: 54 Gy, brachial plexus (Dmax):66 Gy Minimum tumor dose:79.2 Gy.

Radiotherapy will be delivered in twice-daily fractions of 1.8 Gy with 8 to 10 h as interfraction-interval, 5 days per week.

The radiation doses will be specified according to ICRU 50. Lung density corrections will be applied, as well as all standard QA procedures. Technical requirements are the same as in standard practice at MAASTRO clinic.

Inclusion Criteria:

• Histological or cytological proven NSCLC
• UICC stage I-III
• Performance status 0-2
• FeV 1 and DLCO at least 30% of the age-predicted value

Exclusion Criteria:

• Not NSCLC or mixed NSCLC and other histologies (e.g. small cell carcinoma)
• UICC stage IV
• Performance status 3 or more
• FeV 1 and DLCO < 30% of the age-predicted value

• Histological or cytological proven NSCLC
• UICC stage I-III
• Performance status 0-2
• FeV 1 and DLCO at least 30% of the age-predicted value