Metastasis is the spread of cancer cells from any part of the body to other tissues and organs. This spread is named as "locally advanced" if it is adjacent to organs, vessels and regional lymph nodes, and usually corresponds to the third stage in cancer. In such cancers, the tumor is usually minimized with treatments such as chemotherapy and radiotherapy, and then surgery or percutaneous ablation is performed.
If the tumor cells spread through the blood to distant organs such as the liver, lung, bone, and brain, this is named "distant organ metastases" and corespond to the fourth stage in cancer. In such cases, surgical operation is not performed, classical treatment is systemic chemotherapy. However, in some cases, minimally invasive interventional radiological therapies can destroy tumors, reduce tumor burden, or relieve symptoms such as pain and bleeding related to the tumor, thereby significantly improving survival and quality of life in patients.
In which metastases interventional treatments can be useful?
In metastases, percutaneous ablation or arterial treatments can be applied according to the number, size and location of tumors. Percutaneous ablation can be performed in metastases located in subcutaneous soft tissues, and in organs such as liver, lung, pancreas, bone, breast, and thyroid. However, it cannot be done in the stomach, intestine and nerve tissue, but also in tumors adjacent to these structures. For percutaneous ablation, it is necessary to treat each tumor seperately by putting a needle. Therefore, it is preferred that the number of metastases be as few as possible (oligometastases).
In metastases, arterial therapies are mostly applied in the liver. The most commonly used methods are chemoembolization (TACE), radioembolization (TARE) and intraarterial chemotherapy. TACE and TARE are not widely used outside the liver, but intraarterial chemotherapy can be applied in any part of the body. For arterial therapies, it is preferred that the metastases are located in a single organ, such as the liver, or in a single region (such as the arm, leg), and that their feeding vessels are few in number. Percutaneous ablation or arterial therapies are not useful in metastases that have spread over a large number of organs or regions, such as the brain, bone, and abdominal cavity.
Below are the types of metastases where interventional treatments are used most commonly .
1. Liver Metastases:
Liver is the most commonly involved organ by metastases. Especially, the organs of the digestive system such as stomach, intestine and pancreas and others like breast, ovary, lung and kidney cancers frequently metastasize to the liver. The liver is also the organ where interventional cancer therapies are most frequently applied and also most successful. The reason for this is that the liver is a large organ with a homogenous structure, favoring parcutaneous ablation, and that the vessels that feed the tumors (hepatic artery) and the vessels feeding normal tissue (portal vein) are different, favoring intraarterial therapies. Percutaneous ablation (such as radiofrequency, microwave) is preferred in the liver if the metastases are small in number, less than 3 cm, and can be seen on ultrasound or CT. If the metastases are small and numerous, arterial treatments (such as TACE, TARE) are more appropriate.
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2. Lung metastases:
Lung is also one of the most commonly involved organs by metastases. Local treatment options in lung metastases are surgery, radiotherapy and percutaneous ablation. If the metastases are single or several and the lung capacity of the patient is sufficient, all three methods can be applied, although percutaneous ablation and radiotherapy are more preferred because they are less invasive. Surgery and radiotherapy is not suitable if the number of metastases is high, because a too large part of the lung should be removed by surgery and the maximum radiation dose to the lung is exceeded in radiotherapy. Therefore, if there are more than 3 metastases in the lung, the best local treatment is percutaneous ablation.
Location of the metastases is also important; radiotherapy is not suitable for lesions adjacent to the chest wall, heart and and spine whereas cryoablation can be easily performed in such locations. In contrast, centrally located metastases adjacent to the hilum is not favorable for percutaneous ablation methods.
Percutaneous ablation options in the lung are radiofrequency, microwave and cryoablation. All 3 methods are successful in experienced hands. The cost of radiofrequency and microwaves is lower, but general anesthesia may be required for administration, and only metastases less than 2 cm in size can be completely ablated. In contrast, cryoablation is more expensive, but because it is painless,can be done with local anesthesia and large metastases can be treated if sufficient number of needles are used.
In the lung, like elsewhere in the body, metastases should either be few in number (oligometastatic) or slow-growing (oligoprogressive) in order to be useful for the patient. Because, at each session a maximum of 3-6 metastases can be treated and at least 2-3 weeks should be present between the sessions. In addition, it is desirable that the metastases be located solely or predominantly in the lung. Percutaneous ablation is not useful in extensive and rapidly progressive metastases. Moreover, unlike liver, lung metastases are not suitable for interventional arterial treatments.
3. Bone metastases:
Bone metastases are most commonly seen in prostate, breast and lung cancers. The biggest problems for the patient in bone metastases are pain and fracture formation. In such patients, radiotherapy is usually applied first. However: 1. The painkilling effect of radiotherapy is usually starts late (after a few weeks), 2. It is not successful to relieve the pain in about 1/3 of the patients. 3. The pain recurs in a short time in 1/2 of the patients, but . Percutaneous ablation is a veryradiotherapy can not be applied to the same place more than once. Another successful method to relieve pain in bone metastases percutaneous ablation. Cryoablation is especially preferred because it can be administered under local anesthesia and can also rapidly kill the nerves that cause pain. Pain cessation in cryoablation starts immediately after treatment and lasts longer than radiotherapy.
Bone metastases may also cause fractures by weakening the bone tissue (pathological fracture). Particularly, the spine and the hips are prone to fractures which can cause pain, deformation and compression of the spinal cord. This is most commonly seen in a type of bone marrow cancer, called multiple myeloma, and in lung and breast cancer metastases. In such cases, besides percutaneous ablation or radiotherapy, bone can be stabilized by injecting a special cement. This procedure, called vertebroplasty or cementoplasty, can also reduce or eliminate pain caused by fracture.
4. Soft tissue and muscle metastases:
Some cancers can metastasize to the soft tissue or muscle tissue just below the skin. Percutaneous ablation is very successful in such metastases because tumors can be easily seen by ultrasound and are easily accessible from the skin. In soft tissue and muscle metastases, radiofrequency and microwave can also be used, but the ideal method is cryoablation (freezing treatment). Because: 1. Cryoablation can be performed under local anesthesia and is painless. Therefore, it can kill tumors without causing pain in the regional nerves, especially in tumors between the ribs in the chest wall. 2. During cryoablation, the ablation zone (iceball) can be easily seen on ultrasound and CT and sensitive tissues such as skin and nerves can be more easily preserved. 3. It is possible to treat large metastases with a diameter of 6-7cm by increasing the number of needles in cryoablation.