Colorectal cancer is cancer that originates in either the colon or the rectum. Although the colon and the rectum are distinct, the cancers are considered related, and often cancer that originates in the colon spreads to the rectum or vice versa.
Both colon cancer and rectal cancer generally begin with a specific polyp, called an adenoma, that begins to grow in the lining of the colon or rectum. Approximately 95 percent of colorectal cancers begin with this adenoma. The cancers typically develop slowly, spreading first to the center of the colon or rectum.
Colon cancer is said to be metastatic when it spreads beyond the colon and rectum into other organs or body parts. According to Memorial Sloan-Kettering Cancer Center, up to half of those patients diagnosed with colorectal cancer will experience metastases to the liver at some point during their disease.
Surgery
Surgery is the most common treatment for metastatic colon cancer. The surgery obviously removes cancer within the colon and rectum, but additional procedures must also be performed on areas to where the cancer has metastasized.
The liver is the most common site for colorectal cancer metasteses. Approximately 15 percent of patients who are diagnosed with advanced colorectal cancer have liver metastases, with this number rising to 75 percent in those patients as their cancer progresses. This surgery can involve removing the cancer in both the colon and rectum, as well as the metastases in the liver. The liver metastases can be treated either by removing parts of the liver, or by cyrosurgery, in which the liver tumors are frozen but not removed.
Colorectal cancer that metastasizes to the lungs can also be treated by surgically removing spots of cancer on the lung.
Image-Guided Ablation
If surgery is not possible, there is an alternative option for metastases to the liver or lungs. This procedure is called image-guided ablation, and it is performed only by interventional radiologists. This treatment is currently only available for those whose colorectal cancer has metastasized to the liver and the lung.
Image-guided ablation is currently only recommended for patients who are unable to undergo surgery and/or for patients with very small local metastases to the liver or lung. The procedure involves the insertion of a special needle, which delivers heat to areas on the liver or lung where metastases have occurred. The heat kills tumor cells, without affecting the liver or lung functions. For patients with small localized metastases, this treatment is as effective as surgery.
Chemotherapy
Chemotherapy is also used to treat metastatic colorectal cancer. Irinotecan, a newer drug approved for treatment of metastatic colon cancer, has proven relatively effective at Sloan-Kettering, when combined with the chemotherapy agents leucovorin and 5-fluorouracil.
Sloan-Kettering also pioneered studies combining the use of oxaliplatin and cetuximab with leucovorin and 5-fluorouracil. This drug combination was tested on patients with stage IV metastatic colorectal cancer, and was found to slow the growth of cancer cells, lower the risk of recurrence and improve the survival rates in some patients.
Sloan-Kettering also uses several other drugs in the treatment of colorectal cancer. Panitumumab, bevacizumab, and cetuximab (alone or combined with irinotecan) have also been demonstrated to slow the progression of metastatic colon cancer in some patients.
Intrahepatic Pump
A 2006 study at Sloan-Kettering suggested that patients with colorectal cancer that had metastasized to the liver benefited from receiving intrahepatic chemotherapy. Patients who received intrahepatic chemotherapy had slower growth of cancer cells, responded better to the treatment and had a longer survival rate than patients who received traditional chemotherapy .
An intrahepatic pump is a liver pump that allows chemotherapy drugs to be administered directly to the liver, as opposed to intravenously throughout the body.
New Treatments
According to researchers at the University of Texas MD Anderson Cancer Center, new treatments for colorectal cancer, as well as better surgical procedures for liver metasteses, have increased the five year survival rates for metastatic colorectal cancer from 8 percent to 30 percent as of 2009.
However, despite the advances, metastatic colorectal disease is still incurable.
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