Elimination of PTV Margins Based on Online Adaptive Stereotactic Radiotherapy for Early-stage Non-small Cell Lung Cancer or Pulmonary Oligometastases

This trial is testing an advanced radiation therapy technique that adapts the treatment plan in real time to account for tumor movement — such as breathing — in people with early-stage non-small cell lung cancer or a small number of lung metastases. The goal is to deliver highly precise radiation (called stereotactic body radiotherapy, or SBRT) directly to the tumor while reducing the safety margin around it, potentially causing less damage to surrounding healthy lung tissue. **You may be eligible if...** - You are 18 or older with early-stage non-small cell lung cancer (T1-2, N0, M0) that cannot be surgically removed, or up to 3 lung metastases (each under 5 cm) - Your cancer has been confirmed by biopsy or PET-CT scan - You are reasonably functional (ECOG 0–2) and your blood counts and organ function meet minimum levels **You may NOT be eligible if...** - You have more than 3 lung metastases or tumors larger than 5 cm - Your lung function is severely impaired - You have active infections or serious organ problems Talk to your doctor to see if this trial is right for you.