Tumor Embolization is a tool for cancer therapy that helps treat tumors by blocking the blood vessels that supply them. Many tumors such as meningiomas, hemangioblastomas, renal cell metastases, and paragangliomas are hypervascular, thus making surgical resection more difficult and time consuming. Embolization prior to surgery can make resection easier by reducing blood loss during surgical resection and improving visualization of the surgical site. In patients who are not candidates for surgical resection, intra-arterial embolization can provide palliative therapy.
Embolization approaches include transarterial, direct puncture, and a combination of these methods. Ideal tumor embolization is achieved with occlusion of the very small vessels within a tumor, while sparing supply to normal adjacent tissue. Liquid and particulate embolic materials are effective in penetrating small vessels.
Most tumor embolizations are performed via the external carotid arterial supply. Time to surgical resection after embolization may vary depending on tumor type, characteristics, and degree of devascularization. Embolization is often performed within 24–48h of expected surgical resection.
Commonly used embolization materials include poly vinyl alcohol (PVA) particles of varying sizes as well as pledgets of gelatin sponge and microfibrillar collagen. Liquid embolization agents include, n-butylcyanoacrylate, Onyx, and ethanol. Occlusion of large vessels may require use of either pushable or detachable coils.
Onyx is a liquid embolic agent dissolved in dimethyl sulfoxide (DMSO). Upon contact with the blood, DMSO diffuses out and EVOH polymerizes. This polymer hardens on the outer surface first gradually polymerizing toward the core over several minutes. This property allows longer injections of this material. Using this technique, onyx can be used to embolize the tumor bed. This liquid embolic agent can penetrate the tumor bed and can provide controlled embolization of the tumor vascular bed with good penetration. Percutaneous embolization with Onyx has also been described.
Pushable and detachable coils can be used to embolize large (>1.5mm) feeders to tumor beds. They can be an ideal embolization solution for tumors with intra-tumoral shunting. Coils with bio-active components can provide a nidus for thrombosis and eventual occlusion of the vessel. As with nBCA embolization, coils provide proximal occlusion of the blood supply to the tumor bed without the embolization of the tumor vasculature itself. Therefore, surgical resection should follow coil embolization to minimize the development of collateral blood channels.
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