One of the reasons that cancer is a serious disease is its ability to spread to other parts of the body than the location of the primary tumor (i.e. where the first tumor formed). When cancer cells spread to distant lymph nodes, tissues or organs, it is called metastatic cancer, and the metastatic tumor is the same type of cancer as that of the primary tumor. Cancer can spread to any part of the body, but certain areas are more prone to metastases than others.
Although cancer can be hard to control when it has spread, some types of metastatic cancer can be cured or the growth and burden of the metastases reduced or eliminated, leading to improved life expectancy and relieved symptoms if detected at an early stage and handled appropriately. This is especially relevant for liver metastases.
The liver is the second most common organ for metastasis after the lymph nodes. Many solid cancers (i.e. cancers forming tumors) originating e.g. from the lungs, breasts, colon, stomach or pancreas metastasize to the liver, and very often the liver is the first and only site of metastatic disease. Up to 50-70 percent of patients with advanced breast or colorectal cancer develop liver metastases and the liver metastases seem to play a significant role in the cause of death of patients who die with breast or colorectal cancer.
If liver metastases from colorectal cancer are correctly detected and deemed eligible for surgical resection, the survival can be significantly improved, and sometimes full recovery is possible. The five-year overall survival rate for patients undergoing resection for colorectal liver metastases has been reported to be 46 percent compared to only 6 percent for patients who were not subjected to surgical treatment of their liver metastases. Surgical resection of liver metastases from non-colorectal primary tumors such as breast cancer have also been reported to lead to improved survival outcome, although the role of this treatment procedure is less clearly defined than is the case for colorectal liver metastases.
The first line of therapy for colorectal liver metastases is resection of the metastases. For patients considered un-resectable at a first assessment, systemic treatment with anti-cancer medicine can sometimes be used to reduce the metastatic burden, after which the patients may be eligible for resection. If resection is not considered feasible, the liver metastases may be destroyed by other local treatment techniques such as ablation or embolization. Factors affecting whether surgical metastatic resection or other locally directed treatment is feasible include number, size and location of metastases. Correct diagnosis is critical for management of patients with colorectal liver metastases, and imaging plays an essential role in both initial staging (i.e. determining the stage of the cancer), pre-operative planning, monitoring of treatment effect and surveillance for recurrence of disease.
DETECTION OF LIVER METASTASES USING MRI
MRI is an imaging method that uses non-ionizing radiation to create useful diagnostic images. MRI scans use radio waves and strong magnets, and unlike CT and PET-CT, MRI gives no radiation to the patient. An MRI scanner consists of a large, powerful magnet in which the patient lies. Signals are sent to the body by a radio wave antenna, which in turn receives signals back. The returning signal patterns are converted by a computer into very detailed images of parts of the body. To improve the visibility of the body structures, MRI contrast agents, also called MRI imaging drugs, can be administered to the patient prior to the MRI scanning procedure. The MRI imaging drug is a substance that can make abnormalities, such as metastases, appear clearer due to the special magnetic properties of the elements in the contrast agent and thereby increase the sensitivity and/or specificity of the image.
In patients that have, may have or have had a solid extrahepatic cancer disease (i.e. solid cancer originating out-side the liver), MRI liver imaging with an MRI imaging drug is used to detect and localize liver metastases. The imaging drug assists in diagnosis and staging and helps to guide treatment decisions and planning. MRI with contrast is believed to be a very sensitive and useful imaging method to assess and select patients eligible for metastatic resection or locally directed non-surgical treatment. MRI with contrast is also used to determine if a given treatment has been effective, and/or for surveillance of possible recurrence of disease.