By Shinichi Hori
Embolization therapy combined with infusion of antineoplastic agents offers considerable improvement of symptoms for patients, with far fewer complications than systemic chemotherapy, writes Shinichi Hori, Osaka, Japan.
Patients with advanced or recurrent lung cancer usually have lesions invading the mediastinum with serious symptoms. A new and promising treatment for these patients is selective chemoembolization of lung and mediastinal malignancy. The primary lung cancer is supplied mainly by the bronchial artery. In pathological situations, systemic arteries can penetrate into the lung and mediastinum and irrigate neoplastic lesions.
In this new approach, selective arterial infusion of antineoplastic agents concentrates the drugs in the target lesion and reduces systemic exposure. Embolization after the infusion helps in the retention of the drug by inhibiting flushing out by the arterial flow. Well-calibrated spherical material will allow itself to control the occlusion level, which further helps avoid tissue damage. This selective chemoembolization of lung and mediastinal malignancy is a promising treatment procedure for patients who are suffering from various symptoms caused by advanced cancer.
Indication
Tumours invading mediastinum or mediastinal lymph node metastases, causing airway stenosis or vascular stenosis are good indications. Sometimes, urgent transarterial treatment is needed to improve symptoms like dyspnoea, cough, pain or superior vena cava syndrome.
Vascular anatomy
The main artery for mediastinal circulation is the bronchial artery. Branches of the subclavian artery on both sides may feed the lung and mediastinal cancer. The inferior phrenic artery sometimes penetrates the diaphragm and feeds the inferior part of the mediastinum or the tumours in the basal field. The vast majority of lung and mediastinal tumours are seen as areas of hypervascularity and neovascularity.
Diagnostic imaging
Contrast-enhanced CT scan is acceptable for pretreatment imaging, but dynamic study to identify the arterial anatomy is preferable. 3D-imaging is very convenient to know the precise anatomy of the bronchial arterial branching.
Catheter
A 4F guiding catheter system is adequate for a transfemoral or transbrachial approach. A coaxial microcatheter is mandatory for safe and selective catheter insertion to avoid spasm. To maintain a normal flow is the key point for better drug distribution and effective embolization using spherical embolic material.
Antineoplastic agents
Many kinds of antineoplastic agents are necessary. Necrotic effects or tumour shrinkage in mediastinal or pulmonary tumours cannot be anticipated by embolization alone. Combinations of anticancer drugs are selected according to the tumour types, the patients’ treatment histories or their allergic reactions. Cisplatin, docetaxel, fluorouracil, anthracyline or their combinations is usually used for primary lung cancers. The total dose of antineoplastic agent can be reduced compared to systemic chemotherapy.
Embolic material
Spherical embolic material is the only option among embolic agents. The main role of embolic material for cancer treatment is not to obliterate the vessel to the tumour but to eliminate the tumour vasculature. Embolic materials which cause proximal occlusion are not recommended. Repetition of the treatment is almost always necessary. HepaSphere (Merit) seems suitable because of its low irritability. The preferable size is 50–100microns in dry state. The role of embolic materials is not only for the ischaemic effect but also as modulator of chemoagents which can then remain longer in the target lesion than with simple infusion.
Embolization technique
No specific angiocatheter technique is necessary for embolization therapy for thoracic malignancies. Arterial size is generally smaller compared to other organs. Infusion and embolization should be done in state of free blood flow. For this reason arterial spasm or intimal damage should be avoided.
Hybrid angio-CT apparatus which makes it possible to do angiography and CT examination in the same room helps to perform a reasonably priced and effective treatment. A cone-beam CT function may be helpful but the diagnostic value is not good enough to evaluate minute arterial supply. Immediately after completion of infusion, embolization should be commenced. The endpoint of embolization is not arterial occlusion but disappearance of tumour vasculature. In two to four weeks after the procedure, a follow-up examination should be performed.
If a desired result such as tumour regression or symptom relief is obtained, the same treatment should be repeated. If a satisfactory result is not obtained, the regimen of antineoplastic agents should be changed.
Complications
Branches to the spinal cord from the bronchial artery are seldom found, but branching of the bronchial artery from the intercostal artery is quite common. Back flow of embolic material into the intercostal artery should be carefully avoided. The branches from the costocervical artery and thyrocervical artery are also important with regard to communication with the vertebral artery.
Bronchial to pulmonary artery or pulmonary vein shunting should be considered. Pleural lesions after radiotherapy or inflammation can frequently cause shunting from systemic arteries to pulmonary artery or pulmonary vein. If direct communication is evident, embolization should be avoided to prevent a systemic embolic shower.
Summary
Embolization therapy combined with infusion of antineoplastic agents offers considerable improvement of symptoms to patients with far fewer complications compared to systemic chemotherapy. In the management of advanced malignant tumour patients with primary lung cancer, transarterial treatment will play a vital and indispensable role to control life-threatening lesions and extend patients’ life in the years to come.
Shinichi Hori is the director and chief physician at Gate Tower Institute for Image Guided Therapy, Osaka, Japan. He was the inventor of HepaSpheres and is a consultant for Merit Medical
