Recent improvement of surgical care and surgical technique, and increased experience of liver transplantation contributed to aggressive hepatic resection for colorectal liver metastasis (CRLM) including massive hepatic resection after portal vein embolization, associating liver partition and portal vein ligation for staged hepatectomy (ALPPS), and two-stage hepatectomy. For initially unresectable extensive metastasis, some portion of patients with Stage IV could be converted to resectable disease after chemotherapy. However, there are still several unsolved issues regarding diagnosis and treatment of liver metastasis from colorectal cancer.

1. Chemotherapy-associated hepatopathy (CAH) and disappearing liver metastasis (DLM) after chemotherapy
Despite the documented benefits of neoadjuvant chemotherapy in patients with CLM, there are a number of detrimental side-effects that require consideration. In particular, there are a number of chemotherapy related complications which may impair the hepaticparenchyma, thus influencing outcome following resection, including steatosis, chemotherapy-associated steatohepatitis (CASH) and sinusoidal obstruction syndrome (SOS). Another area of concern are those patients with small tumors where the disease may respond in such a way that it is not amenable to detection by conventional imaging techniques such as computed tomography (CT) scanning or intra-operative ultrasound. This may in turn leads to early recurrence after resection where in fact the disease was missed at the original operation. Recently, the problem of ‘missing’ or ‘disappearing’ CRLM has been reported by several institutions. In general, DLM refers to the complete response or disappearance of a liver metastasis on cross-sectional imaging after administration of preoperative chemotherapy. DLM occurs in 5–25 per cent of patients who undergo preoperative systemic therapy, and varies depending on the quality and type of cross-sectional imaging. Management can be challenging because there are conflicting data regarding the natural history of DLM left in situ. In addition, DLM can be difficult to find, making intraoperative decision-making problematic.

2. Diagnosis of liver lesion
Historically, computed tomography (CT) has played an important role in the selection of patients for hepatic resection. The high resolution of multi-detector row CT has increased the sensitivity of detecting CRLM to 70–90 %. The initial staging CT scans sometimes reveal small, equivocal hepatic lesions of < 1 cm in diameter. The incidence of these lesions was reported to range from 12.7 to 25.5 %, and their clinical significance is often unknown at the time of diagnosis. Therefore, additional magnetic resonance imaging (MRI) is often recommended to help differentiate equivocal lesions before surgery. While CT has advantages of widespread availability and shorter scan time with relatively lower costs compared to MRI, it is recognized to have a lower per-patient sensitivity than MRI (64.7 vs. 75.8 %) for detection of CRLM. Moreover, CT is often limited for characterizing small (< 1 cm) lesions which may be overcome by the higher tissue contrast of MRI especially in differentiating cysts from solid lesions. While there is literature reporting the usefulness of either CT or MRI for diagnosing CRLM, there is little known regarding the added value of MRI on CT.


References
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