© Springer International Publishing Switzerland 2015
Leonard Berliner and Heinz U. Lemke (eds.)An Information Technology Framework for Predictive, Preventive and Personalised MedicineAdvances in Predictive, Preventive and Personalised Medicine810.1007/978-3-319-12166-6_99. Minimally Invasive Therapies for Hepatocellular Cancer: Ablation Therapies
(1)
Kern/UCLA Medical Center, Bakersfield, CA, USA
(2)
University of Arizona College of Medicine, Phoenix, USA
(3)
New York Methodist Hospital, Brooklyn, NY, USA
(4)
Weill Medical College of Cornell University, New York, USA
Abstract
Ablation therapy is proving to be a major tool in the anti-cancer armamentarium. The superb diagnostic capabilities of CT, US, and MRI, along with IR techniques, have combined to allow percutaneous tumor ablation to become fairly widespread in availability at major centers. The fundamental concept of ablation is that the extremes of temperature kill cancer. Thus both heating and freezing methods are effectively tumoricidal. Heating options are via radiofrequency, laser, and microwave. The former is utilized most frequently, laser least, and microwave is in its early clinical experience. Other primary methods of percutaneous tumor ablation include cryotherapy (CRYO) and direct chemical injection. While various agents have been injected for direct percutaneous injection into tumors, alcohol ablation is most effective, and has been utilized most frequently. The efficacy of radiofrequency ablation (RFA) is related to the size of the liver tumor. It is accepted that the lesion should not exceed 2.5–3.0 cm to obtain complete necrosis. It has been reported that certain microwave ablation (MWA) devices may allow successful treatment of lesions as large as 5 cm with an acceptable margin of safety. Notwithstanding, RFA commonly is utilized for lesions greater than 3 cm in diameter, occasionally for palliative debulking rather than cure. Guidelines may assist in the selection and use of the more widely used thermal technologies to provide optimal Predictive, Preventive and Personalized Medicine (PPPM). To achieve maximal effectiveness for cure, basic treatment precepts must be understood and adhered to, including: (1) proper patient selection; (2) treatment of the entire lesion; (3) providing adequate tumor margins.
Keywords
Personalized medicineHepatocellular carcinomaLocoregional therapyTreatmentRadiofrequency ablation (RFA)Microwave ablation (MWA)Cryotherapy (CRYO)Alcohol ablation9.1 Introduction
Ablation therapy is proving to be a major tool in the anti-cancer armamentarium. The superb diagnostic capabilities of CT, US, and MRI, along with IR techniques, have combined to allow percutaneous tumor ablation to become fairly widespread in availability. Ablation also may be performed at open surgery or laparoscopically.
The fundamental concept of ablation is that the extremes of temperature kill cancer [1]. Thus both heating and freezing methods are effectively tumoricidal. Heating options are via radiofrequency, laser, and microwave. The former is utilized most frequently, laser least, and microwave is in its early clinical experience.
Other primary methods of percutaneous tumor ablation include cryotherapy (CRYO) and direct chemical injection. The former currently uses argon as the freezing agent and helium for warm-up. While various agents have been injected for direct percutaneous injection into tumors, alcohol ablation, first described by Livraghi [2], is most effective, and has been utilized most frequently.
9.1.1 Mechanisms and Instrumentation for RFA
The mechanisms of tissue destruction differ with the various heating modalities. For radiofrequency ablation (RFA), the mechanism is ionic agitation that causes frictional heating. Tissue death occurs at 60 °C, but in clinical use, the probes generate over 90 °C temperatures. Care must be taken not to overheat, as this can cause charring which is counterproductive to heat therapy, and actually impedes heat propagation and eventual tumor killing. Probes are connected into a generator to disperse the heat effect.
Several type probes and systems exist. Each has features that attempt more complete killing for larger tumors. Thus systems have umbrella type tines, cooling mechanisms to decrease charring, multiple probes (similar to CRYO), different shapes, and variable flexibility to help tailor ablations. Various feedback systems from the different vendors are incorporated into the generators and monitors to guide the operator during the procedures.
9.1.2 Pre-Procedure Requirements
The procedure itself may be performed under US, CT, or MRI guidance. In the United States, CT is utilized most frequently. Contrast enhancement helps depict active tumor, areas of necrosis, and adjacent structures to be avoided. A pre-procedure biopsy is performed at the same setting (with quick stain pathology analysis) if not obtained previously. Coagulation parameters must be normalized prior to RFA. We use general anesthesia and antibiotics, although both are controversial; some operators prefer conscious sedation, and not all interventionalists prescribe prophylactic antibiotics.
9.1.3 The Procedure
Patients are positioned appropriately with access to the tumor entry site, without arms and metal or other artifacts to compromise the imaging appearances of the tumors. Probes must be placed such that, for cure, the entire tumor and a 1 cm circumferential safety margin of kill in normal liver tissue are obtained. Multiple tumors can be ablated in one or more sessions. Results are best with masses 3 cm or less in diameter, and with 3 tumors or fewer in number. Nonetheless, palliative killing of larger or multiple tumors can be an option as well. In the latter case, combination therapy may include ablation along with chemotherapy, radiation therapy, and/or surgery.
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