Methods and compositions for treating, diagnosing and staging cancers, in particular overexpressing the Human Epidermal growth factor Receptor 2 protein (HER2+) given rise to in breast, gastric, gastroesophageal, ovarian, pancreatic cancer and brain tumors, which may be metastatic to the brain or other site. More specifically, the invention provides for Targeted Radionuclide Therapy (TRNT) with a compound of the invention having a peptide that targets the HER2+ cells, a second component for combining metals into complexes through a ring structure (DOTA), and a third radioisotope component, Lu-177 and Ga-68, in which embodiments further include a companion diagnostic, and in which embodiments further include anti-integrin precision medicines for cancers expressing αvβ3 and αvβ5 integrins, HER2+, vascular endothelial growth factor, vitronectin, fibronectin, tenascin, reelin, kindlin and talin. TRNT may be administered alone or in combination with standard-of-care; an immunooncologic and/or chemotherapeutic, adjuvantly or neoadjuvantly.