Most patients with colorectal liver metastases (LMs) receive systemic chemotherapy. This study aimed to determine the significance of a complete response on imaging of LMs after chemotherapy.

Between 1998 and 2004, 586 patients were treated for colorectal LMs in one institution. Of these, 38 with the following criteria were included in the study: fewer than 10 LMs before chemotherapy; disappearance of one or several LMs on computed tomography (CT) scan and ultrasound; surgery with intraoperative ultrasound within 4 weeks of imaging; no extrahepatic disease; follow-up at least 1 year after surgery.

Overall, 66 LMs disappeared after chemotherapy as seen on CT scan. Persistent macroscopic disease was observed at surgery at the site of 20 of 66 LMs, despite CT scan showing a complete response. The sites of 15 initial LMs that were not visible at surgery were resected. Pathologic examination of these sites of LMs, considered in complete response, showed viable cancer cells present in 12 of 15 cases. The sites of 31 initial LMs that were not visible at surgery were left in place during surgery; after 1 year of follow-up, 23 of 31 LMs considered in complete response had recurred in situ. Overall, persistent macroscopic or microscopic residual disease or early recurrence in situ were observed in 55 (83%) of 66 LMs having a complete response on imaging.

In most patients receiving chemotherapy for colorectal LMs, a complete response on CT scan does not mean cure.