Despite improved staging and operative techniques, the rate of incomplete resection (R1) of NSCLC has remained significant over the last decades. Patients with R1 resection have significantly worse survival compared to those with complete resection (R0).

This is a phase I study that investigates the feasibility and safety of delivering Stereotactic Body Radiotherapy (SBRT) to patients with locally invasive NSCLC (cT3-4, N0-1) who are at risk for incomplete resection.

Twenty patients with NSCLC will be treated with SBRT followed by surgery and appropriate adjuvant therapy. Patients will be divided into groups, of 5 patients each, treated with escalating doses (35, 40, 45 and 50 Gy) in 10 daily fractions.

The primary outcome is the feasibility i.e. the ability to complete safely SBRT and surgery (within 6 weeks). Secondary outcomes include acute and late adverse events, R0/R1/R2 rates and secondary surrogates of feasibility.

If successful, this study will lead to further evaluation of pre-operative SBRT in NSCLC.

Inclusion Criteria:

• Patients will be included if they are aged 18 years or older,
• with biopsy proven NSCLC,
• clinically staged T3-T4 marginally resectable i.e. deemed at risk to achieve \