The early detection of liver metastases

Early detection of liver metastases improves outcome in patients treated by chemotherapy, and is also associated with better survival in patients treated surgically. Large liver metastases (greater than about 1–2 cm in size) should be detectable by optimum quality CT or MRI techniques with a high level of accuracy. Microscopic metastases (smaller than 1–2 mm in size) are rarely detected by anatomic imaging methods, but are also rarely discovered at surgery or pathology. Alterations in perfusion caused by angiogenesis in microscopic lesions can sometimes be detected using radionuclide or doppler perfusion techniques. Currently, attention is focused on the early and correct diagnosis of lesions in the size range 2 mm to 2 cm. In this size range, superparamagnetic iron oxide (SPIO) enhanced MRI is probably superior (60% sensitivity) to dual phase CT (45% sensitivity) when compared with surgery and intraoperative ultrasound. Recent developments in CT and MRI promise some further improvement. The value of ultrasonic contrast agents has been shown in efficacy studies, but they are yet to be assessed against state of the art CT and MRI.