Breast cancer (BC) is the most frequent cancer affecting women and, with almost 2.3 million new cases per year, accounts for 11.5% of all new cancer diagnoses. Even though early breast cancer has a high 5-year survival probability (>90% in Europe and North America), metastatic breast cancer (mBC) is still an uncurable disease. The somatostatin subtype-2 receptor (SSTR2), an established tumor marker, represents an interesting new target for novel radiotherapy and diagnostics in mBC. Its expression is highest in tumors that are estrogen receptor-positive (ER+), progesterone receptor positive (PR+), and human epidermal growth factor receptor 2 negative (HER2-). Recent studies have demonstrated that SSTR2-antagonists have superior binding properties compared to prior agonist approaches, making them a promising ligand for theranostics that target tumors with varying SSTR2-expression. NU102 is an SSTR2-antagonist with favorable binding properties and is currently being developed for patients living with mBC. The 61Cu-based NU102 diagnostic component is highly specific and enables delayed imaging, which can detect even the smallest tumors at an early stage with reduced toxicity, as demonstrated in preclinical settings. Based on these imaging data, our 67Cu-based NU102 therapeutic has the potential to enable targeted treatment with improved safety and efficacy at reduced radiation burden.