Treatment of metastatic spinal lesions with a navigational bipolar radiofrequency ablation device: a multicenter retrospective study.

BACKGROUND: Spinal metastatic lesions are a common occurrence among oncology patients and contribute to significant morbidity. Treatment options have been limited in their effectiveness and scope to this point. OBJECTIVE: This study aims to report the safety and efficacy of radiofrequency ablation (RFA) of malignant spinal lesions using a novel RFA bipolar tumor ablation system which includes a navigational electrode containing 2 active thermocouples. STUDY DESIGN: IRB approved multicenter retrospective review of patients receiving RFA as a treatment of metastatic osseous lesions between March 2012 and March 2013. SETTING: This study consists of patients from 5 large academic centers. METHOD: One hundred twenty-eight metastatic lesions were identified in 92 patients who underwent a total of 96 procedures. Cement augmentation was performed when the vertebral body was at risk or had a pathological fracture. Visual analogue scale (VAS) scores were obtained preoperatively as well as postoperatively at the one week, one month, and 6 month time points. Interval change in the patients' pain medications was recorded. Postoperative imaging was used to assess tumor burden at the treated level when available. RESULTS: RFA was technically successful in all of the lesions without complication or thermal injury. Our study demonstrated significant (P < 0.01) decreases in the VAS scores at one week, one month, and 6 months postoperatively. In our largest center, 54% of our patients experienced a decrease and 30% had no change in their pain medications postoperatively. Sixty-two percent of the spinal lesions in this largest institution were located in the posterior vertebral body. Post-ablation imaging confirmed size of ablation zones consistent with that measured by the thermocouples. LIMITATIONS: The main limitations of this study are the heterogeneous patient population, data set, and potential confounding variable of concurrent cement augmentation. CONCLUSION: The STAR System is an RFA device that was safely and effectively used in the treatment of spine metastatic osseous lesions. This new device allows RFA treatment of previously untreatable lesions with resultant reduction in pain that was not controlled by systemic or radiation therapy.

Modeling of the adrenergic response of the human IKs current (hKCNQ1/hKCNE1) stably expressed in HEK-293 cells.

Stable coexpression of human (h)KCNQ1 and hKCNE1 in human embryonic kidney (HEK)-293 cells reconstitutes a nativelike slowly activating delayed rectifier K+ current (HEK-I(Ks)), allowing beta-adrenergic modulation of the current by stimulation of endogenous receptors in the host cell line. HEK-I(Ks) was enhanced two- to fourfold by isoproterenol (EC50 = 13 nM), forskolin (10 microM), or 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (50 microM), indicating an intact cAMP-dependent ion channel-regulating pathway analogous to the PKA-dependent regulation observed in native cardiac myocytes. Activation kinetics of HEK-I(Ks) were accurately fit with a novel modified second-order Hodgkin-Huxley (H-H) gating model incorporating a fast and a slow gate, each independent of each other in scale and adrenergic response, or a "heterodimer" model. Macroscopically, beta-adrenergic enhancement shifted the current activation threshold to more negative potentials and accelerated activation kinetics while leaving deactivation kinetics relatively unaffected. Modeling of the current response using the H-H model indicated that observed changes in gating could be explained by modulation of the opening rate of the fast gate. Under control conditions at nearly physiological temperatures (35 degrees C), rate-dependent accumulation of HEK-I(Ks) was observed only at pulse frequencies exceeding 3 Hz. Rate-dependent accumulation of I(Ks) at high pulsing rate had two phases, an initial staircaselike effect followed by a slower, incremental accumulation phase. These phases are readily interpreted in the context of a heterodimeric H-H model with two independent gates with differing closing rates. In the presence of isoproterenol after normalizing for its tonic effects, rate-dependent accumulation of HEK-I(Ks) appeared at lower pulse frequencies and was slightly enhanced (approximately 25%) over control.