Theranostics integrates molecular imaging with targeted radiopharmaceutical therapy to guide patient selection, treatment personalization, and response assessment using the same or closely related biologic target. The rapid clinical adoption of Lu-177 DOTATATE for neuroendocrine tumors and Lu-177 PSMA-617 for metastatic castration-resistant prostate cancer has shifted theranostics from a niche capability to a capacity-limited service line. Sustainable programs require more than drug procurement: they depend on fit-for-purpose facilities, trained multidisciplinary teams, compliant radiation safety and pharmaceutical quality systems, reliable isotope supply, and reimbursement models that support safe delivery.