What is Transarterial Radioembolization (TARE)

Liver malignancy, be it primary tumors like Hepatocellular Carcinoma (HCC) and Cholangiocarcinoma, is one of the top five most common cancers worldwide and is also a frequent cause of cancer-related mortality. In most of the cases, Hepatocellular Carcinoma (HCC) is often diagnosed late in the intermediate-advanced stage (stage B and C). Because of this often-late diagnosis, radical therapy doesn’t offer much success. While a few curative and/ or palliative therapies might help, but they are not often characterized by a favorable safety or efficacy ratio. Hence for this intermediate to advanced stages of HCC, internal radionuclide therapy is emerging as a good therapeutic option. And according to several studies, Transarterial Radioembolization (TARE) or intra-arterial injection of a radiolabeled embolising agent has led to extremely promising results, both in terms of demonstration of a good tolerability profile and disease control.

Transarterial Radioembolization (TARE) is also simply known as Radioembolization is a combination of Radiation Therapy and a procedure known as Embolization – a minimally invasive treatment in which blood vessels are blocked off to prevent blood flow. In TARE, tiny beads of glass or resin known as microspheres are administered inside the blood vessels that are feeding a tumor so that the supply of blood to the cancer cells can be blocked off. These microspheres are loaded with a radioactive compound – either Yttrium⁹⁰ or Lipiodol labelled with iodine¹³¹ or rhenium¹⁸⁸. Once they get lodged at the tumor site, they deliver a high dose of radiation to the tumor without affecting the normal tissues.

TARE is a palliative treatment (it means that it does not provide a cure) that helps slow down the disease growth and also helps alleviate symptoms. It is often used as a treatment option for patients who cannot undergo other treatment options such as liver surgery or liver transplantation.

Now that we know what TARE is, we should now know about how the procedure is done and what happens before that. A few days before the procedure date, the patient would need to meet an Interventional Radiologist who will actually perform the procedure. The team of doctors (that include medical oncologists, radiation oncologists and surgeons) and the interventional radiologist first study the Triple Phase CT Scan of the patient. This is done to ascertain the feasibility of performing the TARE procedure. The patient is then admitted for a day or in the day care for a hepatic angiography. Hepatic angiography is a procedure that involves the insertion of an angiographic catheter through a puncture in the groin and it helps visualize the arterian anatomy of the patient’s liver. Some blood vessels may need to be coiled to ensure that the radioactive particles are delivered specifically to the tumor site and to also ensure that they do not run off into other organs due to any errant vessels.

The interventional radiologist, while performing the angiography injects a radioactive substance known as Tc99m MAA. This helps him simulate the exact distribution of the TARE particles in the liver before it is actually injected. The patient is then discharged from the hospital so that the interventional radiologist and the other team of doctors study the patient’s images so as to plan the actual procedure and also to calculate the dosage that needs to be delivered. It takes about a week to order the dose.

When the dose is ordered and received, the patient is admitted to the hospital again. An angiography catheter is once again inserted in the liver artery. Now the actual TARE pharmaceutical is injected and it finds its way to the tumors to get trapped there. They start emitting radiation to the tumor that kills it slowly.

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Once the procedure is over, the patient usually needs to spend two-three days in the hospital primarily because the radioactive material administered to the patient renders the patient radioactive for some time and he/ she needs to be kept in relative isolation to protect the attendants, caregivers and the general population from unnecessary radiation exposure.

TARE differs from other embolizing treatments such as Transarterial Chemoembolization (TACE). In TACE, chemotherapy loaded particles are injected into the liver and this modality is only effective in small liver tumors or in cases where there are only one or two secondaries in the liver, whereas TARE can be used even in cases where there is a large tumor in the liver or even when there are multiple tumors in the liver. While TACE is less expensive that TARE, the post-procedure side effects of TACE may in fact, be slightly more sever that TARE.

While speaking of side-effects, Transarterial Radioembolization (TARE) is typically well-tolerated. In some cases, patients have experienced some transient pain in the upper abdomen. In some other cases where there is extensive liver involvement, there may be a worsening of the liver function and in some extremely rare cases, an acute liver failure. However, complications because of TARE are extremely rare, with the incidence of serious complications being less than 1%.

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