Achieving secondary resectability remains a major challenge in patients with initially unresectable colorectal liver metastases (CRLM).

We report a 46-year-old patient with rectal adenocarcinoma and three large synchronous unresectable liver metastases who achieved a durable response following an intensive multimodal strategy. FOLFOX plus panitumumab induced partial regression, while selective internal radiation therapy (SIRT) led to extensive tumor necrosis, enabling curative-intent extended left hepatectomy combined with microwave ablation. The patient remains in remission without systemic therapy more than six months after treatment completion.

This case highlights the role of SIRT in conversion strategies for large oligometastatic CRLM.