Summary: Drug-tolerant residual disease (DTRD) after the initial maximal response to a systemic therapy can serve as a tumor reservoir for the development of acquired drug resistance and represents a major clinical challenge across various cancers and types of therapies. To unlock the next frontier in precision oncology, we propose a fundamental paradigm shift in the treatment of metastatic cancers with a sharpened focus towards defining, monitoring, and therapeutically targeting the DTRD state.