The second group of minimally invasive interventions in cancer patients are transarterial treatments. These treatments are performed by placing a tiny catheter from the groin into the feeding arteries of the tumor (selective catheterization). To do this, special angiography machines are used, which are different from the ones used in coronary angiography.
How are they done?
For transarterial treatments, first the patient is put on the angiography table, the groin is disinfected and numbed with local anesthetic, and a small tube (sheath) is placed into the groin artery. Then, a tiny catheter is inserted through this tube and advanced to the region where the tumor is located. After that, multiple angiography films are taken to identify the feeding arteries of the tumor.
In some centers like ours, special angiography devices equipped with a “cone beam CT” are present, which can generate both angiography and computed tomography images simultaneously in 3 dimensions. With such devices, it is possible to idelinesntify the feeding arteries of tumors much more easily and accurately. After these arteries are seen on the angiography screen, special catheters are placed into these vessels and transarterial treatments are performed.
What transarterial treatments are performed?
Once the feeding arteries of the tumor are catheterized, four kinds of transarterial treatments can be performed.
Intraarterial chemotherapy is mostly performed for cancers located in the neck, eye, head, liver, breast, lung and extremities (arms and legs).
It is generally done via angiographies performed with 1-3 weeks intervals. If the chemotherapy is planned for a long time or the patient does not want to undergo angiography frequently, an arterial port catheter can also be implanted. In this technique, a soft catheter is placed into the feeding vessels via angiography, and the other end of the catheter is attached to a small reservoir (port), which is then implanted beneath the skin at the groin. In this way, intraarterial chemotherapy can be performed whenever needed via the arterial port, instead of doing an angiograpy in each session. Arterial ports can be used for months or even for years unless they are occluded or infected. These ports are mostly used for the intraarterial chemotherapy of primary and metastatic liver tumors.
Another form of intraarterial chemotherapy is “isolated limb infusion” (ILI). This technique can be used in tumors located solely in an arm or leg. For ILI, first the artery and vein of the extremity are punctured and a catheter is placed into each vessel. Then, a tourniquet is applied to the arm or leg, and the extremity is isolated from the systemic circulation. During the infusion, the blood is aspirated from the vein, mixed with a high dose chemotherapeutic agent (melphalan), warmed to 40-42 degrees and injected into the artery of the extremity. This process is repeated continuously for 20-30 minutes and the extremity is exposed to a very high dose intraarterial chemotherapy. Since the drug dose not pass to the systemic circulation, there is very mild or no side effects, and thus, the concentration of the chemotherapeutic drug can be increased to 20-100 times than the normal. ILI is mostly employed for the skin metastases of malignant melanoma and special soft tissue tumors called sarcoma.
What are the advantages and disadvantages of transarterial treatments?
The most important advantage of transarterial treatments is their increased local effect to the tumor, since they are done directly via the feeding vessels, and decreased systemic side effects, since other tissues or organs are not affected. For example, in intraarterial chemotherapy, the drug concentration in the tumor is about 10-20 times higher than in systemic chemotherapy, and thus, its tumor-killing effect is much higher but side effects to other organs are fewer. Likewise in embolization, chemoembolization and radioembolization, only the tissue fed by the embolized vessels is affected, and other tissues or organs are not harmed. On the other hand, transarterial therapies require multiple sophisticated angiography sessions. To do this, a special angiography device, which is totally different from the one used in cardiology, and a well-trained staff are necessary. For this reason, transarterial cancer treatments are performed in a limited number of centers worldwide.
What factors affect the treatment results?
Although they have the potential to kill the cancerous tissue, transarterial treatments are less likely to achieve complete destruction of the tumor compared to percutaneous ablation methods. For this reason, if the tumor is suitable for surgery or percutaneous ablation they must be the first choice treatments. However, transarterial treatments can be effective in a larger area than these therapies, therefore, they can be used in larger and multiple tumors, which are not suitable for surgery or percutaneous ablations. In such cases, transarterial treatments can decrease the number and size of the tumors and make them suitable for percutaneous ablation or surgery, or they can increase the survival and life quality of the patient. In most patients, classic chemotherapy and/or radiotherapy are first tried, and if they are not sufficient, then transarterial treatments are performed alone or in combination with these classic therapies.
For the success of transarterial treatments, the vascular structure of the tumor is important. In general, cancers with an increased blood supply and vascularity respond better to transarterial treatments. Besides, a single feeding vessel versus multiple feeders, and straight-large arteries versus tiny and tortuous arteries are favorable, because it is technically easier to place a catheter into such vessels.
The most commonly performed transarterial treatment is intraarterial chemotherapy. This treatment can be applied to any region that can be reached with a microcatheter. However, it is more frequently performed for tumors located in the liver, eye, head, neck, brain, lung, breast, pancreas and extremities. Similarly, embolization can also be applied to any tumor that can be reached with a microcatheter. However, the use of chemoembolization and radioembolization is more limited. Although the use of chemoembolization has been described in many tumors outside the liver, and radioembolization has been successfully used in the kidney and spleen, the application of both techniques to tumors located outside the liver is considered experimental at present.
What kind of tumors are most suitable for transarterial treatments?
• All kinds of primary and metastatic liver tumors.
• Locally advanced inoperable lung tumors that have a few or no distant metastases.
• Tumors located in other organs, that may become suitable for ablation or surgery, if reduced in size or number with transarterial treatments.