**4.1. Radiofrequency ablation of osteoid osteoma**

Osteoid osteoma, a benign tumor of the bone. It is the third most common primary benign bone tumor, representing approximately 10–12% of benign bone tumors . It generally affects children and young adults. Approximately 80% of patients are between 5 and 24 years of age, with a male: female ratio of 3:1. Clinically, pain is the most common presenting symptom and is described as severe, sharp, boring, and typically worse at night, and improves with nonsteroidal anti-inflammatory drugs [5]. The growth potential of these benign lesions is limited, with a maximum diameter rarely exceeding 15 mm. However, the inflammatory response leads to the characteristic severe pain. The consequences of these lesions include growth deformities when tumors are located in the long bones and scoliosis when the posterior elements of the spine are involved [6]. Patients who cannot tolerate the symptoms or nonsteroidal anti-inflammatory drugs require intervention for pain relief and/or to prevent growth disturbance. Traditionally, surgical resection was the treatment of choice. During open surgery the nidus of the tumor is often difficult to visualize and to prevent recurrence a wide resection margin may be required. This results in many complications such as hematoma, infection, and fracture. In addition, surgical treatment may require a long period of hospitalization, a period during which the patient cannot bear weight on the affected limb resulting in delayed resumption of physical activity [7]. The optimal method of treatment for osteoid osteoma would involve minimization of bone removal with avoidance of grafting and fixation while ensuring complete destruction of the tumor nidus in a single session. During the past two decades, many attempts have been made to minimize bone removal to decrease the risk of postoperative complications. Percutaneous resection utilizing CT guidance to guide trephines and drills has been described. However, the complication rates are as high as 24% and include fractures, muscular haematomas, paraesthesia, skin burns, transient paresis, and osteomyelitis [8]. Radiofrequency ablation has proved to be an effective method for the treatment of many malignant and benign tumors. RF ablation for the treatment of osteoid osteoma was first described in a four-patient series in 1992 [9]. Since the promising results of Rosenthal et al in the management of osteoid osteoma with RF ablation a large number of studies evaluating RF ablation of osteoid osteoma have been reported in the peer-reviewed medical literature. Most of these studies found very high technical success rates (100%) and good primary success rates with a single session of ablation ranging from 76% to 100% (fig 2 and fig 3). Today, percutaneous CT-guided RF ablation is an effective and safe minimally invasive procedure for the treatment of osteoid osteoma in all ages. It has high technical and clinical success rates (10-12)

148 Hyperthermia

metastases and many other condition.

engineers, physicists and biotechnologists

**4.1. Radiofrequency ablation of osteoid osteoma** 

Several studies have been published reporting successful use of radiofrequency ablation in the following conditions: as an alternative to surgical resection for debulking of primary and metastatic malignant neoplasms, removal of primary or metastatic malignant neoplasms, treatment of distant metastases of medullary thyroid carcinoma, treatment of metastatic gastrointestinal stromal tumors (GIST) with limited progression, treatment of osteoid osteoma, as a less invasive alternative to surgical resection of the tumor ,treatment of soft tissue sarcoma of the trunk or extremities in symptomatic persons with disseminated

There is growing research and experimental and investigational studies interest in the use of hyperthermia for treatment of many other clinical conditions. But these studies need to improve its clinical outcomes to be implemented in the practical life. Examples of these studies include; curative treatment of primary or metastatic malignant neoplasms (e.g., breast cancer, kidney cancer including renal angiomyolipoma, lung cancer, and pancreatic cancer) in persons who are able to tolerate surgical resection, treatment of malignant bile duct obstruction due to insufficient evidence in the peer-reviewed literature. Treatment of Barrett's esophagus, treatment of hepatic tumors, treatment of benign prostatic hypertrophy (transurethral needle ablation or TUNA) ,cardiac catheter thermal ablation is now standard of care for a variety of cardiac arrhythmia types (irregular heart beat rhythm) ,endometrial ablation is clinically used to treat endometrial bleeding ,intravascular heating can eliminate varicose veins with laser or radiofrequency current, laser and other thermal methods treat excessive subcutaneous fat, which can contribute to obesity and metabolic disorders including diabetes. Hyperthermia can also be used to activate cytotoxic effects of chemotherapy within tumors, thereby sparing normal tissue, when the drugs are encapsulated in thermally sensitive nanoparticles. As a result of these and other clinical applications, combined with a rapidly expanding research base, interest in thermal medicine is rapidly growing, attracting the attention of laboratory and clinical researchers, physicians,

Osteoid osteoma, a benign tumor of the bone. It is the third most common primary benign bone tumor, representing approximately 10–12% of benign bone tumors . It generally affects children and young adults. Approximately 80% of patients are between 5 and 24 years of age, with a male: female ratio of 3:1. Clinically, pain is the most common presenting symptom and is described as severe, sharp, boring, and typically worse at night, and improves with nonsteroidal anti-inflammatory drugs [5]. The growth potential of these benign lesions is limited, with a maximum diameter rarely exceeding 15 mm. However, the inflammatory response leads to the characteristic severe pain. The consequences of these lesions include growth deformities when tumors are located in the long bones and scoliosis when the posterior elements of the spine are involved [6]. Patients who cannot tolerate the symptoms or nonsteroidal anti-inflammatory drugs require intervention for pain relief and/or to prevent growth disturbance. Traditionally, surgical resection was the treatment of choice. During open surgery the nidus of the tumor is often difficult to visualize and to

**Figure 2.** Technique of RFA of osteoid osteoma in a 12-year-boy with chronic right hip pain. a Radiograph of the pelvis shows an ill-defined area of dense sclerosis in the medial aspect of the proximal femoral shaft (arrow). b Bone scan shows active uptake at the site of the dense sclerosis consistent with the diagnosis of osteoid osteoma. c CT scan shows the nidus located deep to the cortex and surrounded by dense new bone. The radiopaque markers on the skin surface are for planning the skin entry point. d Axial 1-mm CT slice shows the correct position of the tip of the RF electrode within the centre of the nidus. e Follow-up CT after 15 months shows sclerosis within the nidus (12)

Hyperthermia and Radiology 151

**4.3. Radiofrequency ablation of pancreatic cancer** 

Radiofrequency ablation has been used as a treatment of pancreatic cancer for a number of years in Japan. Current evidence of effectiveness of RFA for pancreatic cancer consists of case reports and a phase II (safety) study; the latter concluded that RFA was a relatively safe treatment for pancreatic cancer. However, this evidence is insufficient to draw conclusions about the effectiveness of RFA for this indication. Girelli et al (2010) examined the feasibility and safety of RFA as a treatment option for locally advanced pancreatic cancer. A total of 50 patients with locally advanced pancreatic cancer were studied prospectively. Ultrasoundguided RFA was performed during laparotomy. The main outcome measures were shortterm morbidity and mortality. The tumor was located in the pancreatic head or uncinate process in 34 patients and in the body or tail in 16; median diameter was 40 (inter-quartile range [IQR] of 30 to 50) mm. Radiofrequency ablation was the only treatment in 19 patients; it was combined with biliary and gastric bypass in 19 patients, gastric bypass alone in 8, biliary bypass alone in 3 and pancreatico-jejunostomy in 1. The 30-day mortality rate was 2 %. Abdominal complications occurred in 24 % of patients; in half they were directly associated with RFA and treated conservatively. Three patients with surgery-related complications needed re-operation. Reduction of RFA temperature from 105 degrees C to 90 degrees C resulted in a significant reduction in complications (10 versus 2 of 25 patients; p = 0.028). Median post-operative hospital stay was 10 (range of 7 to 31) days. The authors concluded that RFA of locally advanced pancreatic cancer is feasible and relatively well tolerated, with a 24 % complication rate. This was a feasibility and safety study; it did not

provide any data on the effectiveness of RFA in treating pancreatic cancer (16).

Several authorities have noted that RFA of renal tumors is a promising investigational alternative to partial or total nephrectomy. Studies performed have focused on the technical feasibility of RFA of renal tumors. Prospective clinical studies are needed to determine if RFA of renal cell carcinomas improve survival and are as effective as total or partial

An assessment conducted by the National Institute for Clinical Excellence in 2010 reached the following conclusions about RFA of renal tumors: " A meta-analysis of 47 studies (nonrandomized comparative studies and case series) including a total of 1375 tumors treated by RFA (n = 775) or cryoablation (n = 600) reported local tumor progression (defined as radiographic or pathological evidence of residual disease after initial treatment, regardless of time to recurrence) in 13% (100/775) and 5% (31/600) of tumors respectively at a mean 19 month follow-up (p < 0.001). The meta-analysis reported progression to metastatic disease in 2% (19/775) of tumors treated by RFA and 1% (6/600) of tumors treated by cryoablation�(p = not significant)" (19). Another assessment of the evidence for RFA of kidney cancer prepared by the Canadian Coordinating Office for Health Technology Assessment (20) reached the following conclusions: "RFA is emerging as a useful alternative to nephrectomy in the management of some types of kidney cancer. It appears to be useful for smaller, non-central

**4.4. Radiofrequency ablation of renal tumors** 

nephrectomy (17-18)

**Figure 3.** RFA of osteoid osteoma in a 14-year-old girl. a MR images shows a small, well-defined lesion in the proximal tibial epiphysis. b CT during percutaneous RF ablation shows a radiolucent nidus with central calcification surrounded by a dense rim of sclerosis. Note markers for planning the skin entry point. c CT shows the bone biopsy probe tip at the margin of the nidus . d CT shows the tip of the RF electrode within the nidus after slight withdrawal of the penetrating cannula. e Control image obtained immediately after the intervention shows the biopsy tract with no bleeding(12)
