Gadolinium Recruiting Phase 2 Trials for Lung Cancer / Stereotactic Radiation / Gastrointestinal Tract Cancer / Nanoparticles / Brain Cancer / Melanoma / Whole Brain Radiation / SRS / SRT / Colorectal Cancer / Brain Neoplasm / HER2/Neu-positive Breast Cancer / Cystic / Brain Metastases / Breast Cancer / AGuIX Treatment