The Development and Application of a Radiofrequency (RF) Interstitial Hyperthermia System to Prostate Cancer.

To heat a greater volume less invasively and more effectively, we developed a multi-channel RF interstitial hyperthermia system compatible with the high-dose rate Iridium-192 remote after-loading system (Ir-192 RALS). The system is composed of eight channel RF signal generators, which can be controlled individually. Each RF generator can be connected to 1) an internal electrode, which was originally an Ir-192 RALS applicator ; and 2) a shared rectangular external electrode made of aluminum. By means of experiments using an agar phantom and an animal liver, we evaluated the heating characteristics, safety, and feasibility of this system.Subsequently, we applied trans-perineal RF interstitial hyperthermia and Ir-192 RALS for localized prostate cancer (PC). Under trans-rectal ultrasound guidance, 18 stainless applicators for Ir-192 RALS were inserted into the prostatic gland and seminal vesicles in an optimized pattern. Eight applicators were used as internal electrodes and were electrically insulated along the length of subdermal fat tissue using a vinyl catheter. The temperature inside the prostate and rectum was monitored continuously. Hyperthermia was performed following the first and fourth Ir-192 RALS (total of 24 Gy / 4 fractions). Total doses of 46 Gy were also delivered by linear accelerator.There were no complications, such as infection, bleeding, fat necrosis, or burns. Histological examination after the treatment revealed cancer cell death and necrosis. MRI and CT images showed a well-demarcated, low-intensity area at the center of the prostate reflecting the necrotic area.Trans-perineal hyperthermoradiotherapy is a feasible and effective therapeutic alternative for the treatment of patients with localized PC. In addition, our system is compatible with the Ir-192 RALS, allowing for less-invasive interstitial hyperthermoradiotherapy by eliminating the trauma of needle re-insertion.