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Regional Therapy for Colorectal Cancer Liver Metastases
Patients who have colorectal cancer that has spread to the liver (liver metastases) and cannot be removed by with surgery may receive regional therapies to deliver targeted treatment to the liver to diminish the size and number of tumours. The liver is a unique organ in that it receives two separate blood supplies: the blood supply via the hepatic artery which serves as the primary supply for liver tumours, and the blood supply through the portal vein which supplies most of the normal liver cells. Since the hepatic artery is the dominant supplier of blood to liver tumours, selective delivery of cancer therapies to the tumours can be achieved while mostly sparing normal liver tissue as well as surrounding tissues outside the liver, helping to limit the systemic side effects of such therapies. There is, however, a lack of evidence from randomized controlled trials to effectively identify the optimal treatment approach to integrate regional therapies in the management of colorectal cancer liver metastases.
Randomized controlled trial (RCT): RCTs are a type of clinical trial that are used in cancer research that randomly assign participants into the experimental group (those receiving the novel treatment) or a control group (those receiving the standard of care treatment). RCTs are considered the gold standard in cancer trials.
Types of regional therapies for colorectal cancer liver metastases:
1. Hepatic arterial infusion pump (HAIP) chemotherapy is a small, disc-shaped device that is surgically implanted just below the skin of a patient with colorectal cancer that has spread to the liver. It is connected via a catheter to the hepatic artery of the liver, allowing 95% of the chemotherapy that passes through the pump to stay localized to the liver. HAIP chemotherapy can be safely given together with systemic chemotherapy and is associated with a high objective response rate (proportion of patients with a complete response or partial response to treatment) as well as a high rate of conversion to resectable tumours (tumours that can be removed successfully by surgery).
2. Transarterial chemoembolization uses microscopic beads (“microspheres”) that are coated with the chemotherapy drug irinotecan to deliver localized chemotherapy through the hepatic artery. It is associated with high response rates in the liver and has a well-established safety profile among patients with colorectal cancer liver metastases.
3. Transarterial radioembolization involves the use of microscopic beads (“microspheres”) that are impregnated with the radioactive yttrium-90 (y90) which are selectively delivered through the hepatic vasculature to the target tumours. Though this regional therapy achieves high rates of response within the liver, it is not associated with improvements in overall survival or quality of life when it is used as a first-line (initial) treatment or second-line treatment for patients with colorectal cancer liver metastases.
In summary, the ideal treatment approach for patients with colorectal cancer liver metastases is one that aligns with the patients’ values, preferences and overall philosophy of care. After progression on chemotherapy, the three above-mentioned regional therapies are valuable treatment options to consider among patients who have colorectal cancer metastases in the liver. Further research is needed to best define the role of regional therapies in this subset of patients.
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