Liver embolization therapy is a directed therapy that takes advantage of the unique vascular supply of the liver to go after inoperable cancers that form in the liver. The method is seeing increasing use in NET cancer patients because they are often not diagnosed until the metastases in the liver are well along in their development and have colonized the liver to the point surgery is not a good option.
Not everyone is a good candidate…
Unlike the other organs in the body, the liver is not primarily fed by an artery. Rather, it gets 80-90 percent of the nutrients it needs through the hepatic portal vein system before shipping that blood onto the heart to be sent to the lungs for oxygen. The oxygenated blood then returns to the heart to be distributed to the rest of the body.
The hepatic artery does carry some nutrients to the liver, but the liver is not very dependent on those supplies. Blocking it or its downstream capillaries doesn’t seem to do the liver any longterm harm. But it can do the tumors significant harm. They get all their food and oxygen coming in on that arterial pathway. They even create their own vasculature to steal supplies to help them grow.
The method is seeing increasing use in NET cancer patients…
Regardless of where a tumor forms in the body, that desire for blood flow creates a weakness in any tumor. If we can prevent blood vessels from forming, the tumor will starve to death in short order. Several different drugs are designed to try to do this (angiogenesis inhibitors)–they may be the only option for affecting the vasculature of tumors growing in most places in the body. You can’t easily block an artery that is feeding both cancerous and healthy tissue.
But the peculiar way the liver works means blocking arteries is not entirely–or necessarily–a bad thing, and that opens up another avenue of attack. If we can block the small arteries leading to a tumor, then the tumor will starve to death the same way a city under siege does. There may be some damage to surrounding tissue, but that damage is comparatively minor–and the liver is very good at repairing itself.
But it can do the tumors significant harm.
Researchers have developed three methods of liver embolization: bland (TAE), chemo (TACE), and radiation (TARE). All three use small beads to block the blood supply to the tumors, but the beads are treated with drugs before being inserted in chemoembolization, and impregnated with radiation in radioembolization. The bland embolization beads are sterile, but not treated with anything. They simply block the blood supply to the tumor.
The chemo and radiation treated beads deliver their payloads directly to the tumor, which means less chance of damage to surrounding healthy tissue and fewer side effects than regular chemo or external radiation treatments can entail. For NET cancer, TACE beads can be treated with a number of different chemical agents, either singly or in combination; Y90 is used with the irradiated beads used in TARE for NET cancer: SIR-spheres or TheraSpheres, the primary difference being how big a dose of radiation each sphere carries.
…the tumor will starve to death…
The basic procedure is the same for all three forms of liver embolization. A small tube is inserted into the femoral artery and threaded up to the liver. That tube is then used to place the tiny beads into the arteries leading to the tumors. The doctors only do one lobe at a time. The second lobe is done about a month after the first, if necessary.
Liver embolization can be repeated later if the tumors return or begin to grow again if the first round of embolization is successful. The procedure may improve the quality of a patient’s life and extend that life. But it does not work for everyone, and none of these treatments offers a cure for the disease. It can only reduce the size and number of the tumors in the liver and may provide some relief from the symptoms of the disease for a time.
The basic procedure is the same for all three forms…
There is a wide range of side effects–ranging from minor to severe, including–among the most negative–liver failure, kidney failure and death. But the more severe side effects are rare–death occurs in less than five percent of all cases, and is less frequent the more experience the doctor has with the procedure.
Good news–bad news
At least one of the side-effects, postembolization syndrome (fever, nausea, vomiting, abdominal pain, and elevated liver enzymes), occurs in most patients. Strangely, the severity of that one side-effect may be an indicator of the success of the procedure rather than an indication of failure, as those with more severe versions of it seem to have had a better reduction in tumor size than those with milder reactions.
The procedure may improve the quality of a patient’s life…
Not everyone is a good candidate for this procedure and it should not be used if the tumors can be dealt with surgically in any event. And even for those who are not good candidates for surgery, it is not always possible. The greater the tumor burden, the less likely it is to be an option. Where exactly the tumors are in the liver also makes a difference.
A final point
The purpose of this article is not to give medical advice. Rather, it is designed to provide basic information about liver embolization for a non-medical audience. As with any medical procedure or treatment, you need to discuss your particular case with your doctor.