'SOURCE - LUNG' Stereotactic Ablative Radiation Therapy Of UltRaCEntral LUNG Tumours (SOURCE Lung)

This study tests a specialized type of radiation therapy called stereotactic ablative radiotherapy (SABR) — a highly precise, high-dose radiation delivered in a few sessions — for tumors located in a challenging central area of the lung near major airways and blood vessels. It aims to find the safest effective dose for these difficult-to-treat tumors. **You may be eligible if...** - You are 18 or older - You have a confirmed primary lung cancer (non-small cell) or a single cancer spread (metastasis) to the lung that needs local treatment - Your tumor is located in the central lung area and meets specific radiation planning criteria - You cannot have surgery, or you declined surgery - You are in generally good health (ECOG performance status 0-2) with a life expectancy over 6 months **You may NOT be eligible if...** - Your tumor is directly touching your esophagus - You have evidence of spread to lymph nodes or other organs (for primary lung cancer) - You have conditions that make you more sensitive to radiation (e.g., certain hereditary syndromes or pulmonary fibrosis) - You received chemotherapy or targeted therapy within 3 months before planned radiotherapy - You previously had radiation to the chest or middle chest area - You cannot lie still for a 4D CT scan Talk to your doctor to see if this trial is right for you.