Experimental Studies of Intralymphatic Administration of Radiotherapy

The clinical use of endolymphatic radiotherapy has received increased interest in recent years (1–3, 5–7, 8, 11, 15, 20, 21). While studying body distribution of Ethiodol following lymphography, we became interested in this question. The high concentration and long biological half-life of radioactive substances in the lymph system in contrast to the rest of the body was striking (13). These observations suggest that this method of treatment has the potential of being an excellent adjunct to conventional radio- or chemotherapy in patients with certain malignant diseases. We were alarmed, however, by the high concentration of activity in the lung and our inability to control overflow of radioactive material from the lymph system to the general circulation. Of less importance, yet still disturbing, was the fact that, because we did not know how much of the injected material stayed in the lymphatic system, dosage calculations became difficult or impossible. In addition, since only short-range radiation is advantageous, nodes with large metastases are not affected. Knowledge of the condition of these nodes prior to the administration of radioactive material will therefore be a great advantage. We felt that an investigation should be conducted to study the physiologic response and dynamics of the lymphatic system during and after administration of endolymphatic therapy to humans. Experiments were designed to answer the following questions: 1. Can a method be developed which will protect the body from overflow of radioactivity yet assure saturation of the involved nodes? 2. What effect does previous diagnostic lymphography have on the retention ability of a lymph node? 3. Is it possible or advantageous to increase the uptake of radioactivity of nodes by infusion of large volumes through the node? If so, should this be done by a continuous or by a pulse-type infusion? This report summarizes a group of experiments designed to answer these questions. Material and Methods Thoracic Duct Bypass: Our first experiment was designed to measure the efficiency of thoracic duct cannulation in protecting the lung from irradiation. An isolated infusion cycle was established in dogs by injecting the peripheral lymph vessel and cannulating the thoracic duct in order to remove any excess of oil before it reaches the general circulation. No serious complications have been reported with this procedure in normal ducts cannulated for other reasons. Cannulation is performed under the local anesthesia after a small incision in the supraclavicular area is made. The catheter is removed after samples show that radioactivity has decreased sufficiently (twenty-four to thirty-six hours), and a normal flow is promptly established. The concept is illustrated in Figure 1.