Minimally Invasive Tumor Therapy (MITT)

Department of Radiology, Charité – Universitätsmedizin Berlin

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References

Gebauer B, Collettini F, Bruger C, Schaser KD, Melcher I, Tunn PU, Streitparth F. Radiofrequency ablation of osteoid osteomas: analgesia and patient satisfaction in long-term follow-up. Rofo. 2013 Oct;185(10):959-66.

Minimally Invasive Treatment of Benign Bone Tumors in Children – Osteoid Osteoma

 

Bone tumors are benign (noncancerous) or malignant tumors that occur in the bone. Primary bone tumors start in cartilage or bone tissue, while secondary bone tumors (metastases) typically spread to the bone from cancer elsewhere in the body.

 

Many types of primary bone tumors are especially common in children, most likely because their bones are still growing. The most common symptom of childhood bone tumors is pain. A plain X-ray (radiograph) is often sufficient for diagnosis. Many bone tumors have a characteristic X-ray appearance, which, along with the patient’s age and the body site in which they are found, allows a diagnosis to be made. If the radiograph does not provide enough information, the doctor may order a magnetic resonance imaging (MRI) study or a computed tomography (CT) scan.

 

An osteoid osteoma (OO) is a primary bone tumor with characteristic signs and symptoms (pain at night) and a typical appearance on X-ray. Pain is often dramatically relieved by a nonsteroidal anti-inflammatory drug (NSAID) like aspirin. Osteoid osteomas account for about 10 percent of all benign bone tumors. They typically arise in the long bones of the legs (and less commonly of the arms) or in the spine. Osteoid osteomas are benign and do not spread to other parts of the body. Nevertheless, these tumors may cause severe pain, which, for the mostly young patients, can be difficult to endure. As a result, an osteoid osteoma can lead to abnormal positioning and overloading with joint wear and tear.

 

Aim of Treatment

 

The aim of treating a patient with an osteoid osteoma is to relieve pain. In the past, when only surgery was available, these patients often needed a large excision to ensure complete tumor removal. About 15 years ago, an alternative, less invasive treatment option became available for these patients. This method uses heat to destroy tumor cells and is known as thermal ablation. It is now the standard treatment for osteoid osteoma. In medicine, ablation (from Latin ablatio - taking away) is the removal of biological tissues. In a wider sense, the term is used to refer to the destruction or inactivation of (tumor) cells using radiation, heat, electricity, biomechanical means, or chemical agents. The aim of ablation treatment is to completely inactivate all cells in the target area, eventually resulting in the formation of a scar.

 

Minimally Invasive Thermal Ablation Using RFA or Laser

 

Heat treatment, or thermal ablation, of an osteoid osteoma destroys both the cells that produce prostaglandin (believed to prompt pain) in the center (nidus) of the tumor and the nerves that conduct the pain. This is achieved by heating the osteoid osteoma cells to a temperature of 60°C - 90°C. Heat is generated in the diseased tissue by applying radiofrequency (RFA) or laser energy (LA). RFA is the most commonly used thermal ablation technique. It is also the most widely studied and best understood technique. RFA involves introducing a special probe with tiny electrodes into the diseased tissue. The probe is usually inserted into the body through a small skin incision using computed tomography (CT) for guidance to ensure correct positioning of the probe in the target area. Once the RFA probe is in the desired position inside the tumor, an alternating current field is generated at the probe tip to heat the diseased tissue to the target temperature.

 

Figure 1: Mechanism of radiofrequency ablation (RFA). The drawing shows the tip of the RFA probe inside the tumor (red) in the long bone of the right thigh. The probe is attached to a generator which sends an alternating electrical current or radiofrequency energy through the probe. This generates frictional heat by inducing movement of ions around the probe tip.

 

In laser ablation, a light wave conductor is positioned inside the tumor for direct delivery of laser energy. With this technique, heat for thermal ablation is generated by the absorption of photons (light particles) in the tumor tissue.

 

Thermal ablation of an osteoid osteoma should always be performed under general anesthesia since drilling into the bone tumor and heating can be very painful. Laser treatment and RFA have similar success rates. Ninety percent of patients are cured and experience permanent relief of pain after a single ablation procedure. In the remaining ten percent, some pain remains or the pain returns after some time. In these cases, treatment must be repeated.

 

Some rare complications can occur. They include bleeding and hematoma (collection of blood outside blood vessels), infection, abscess formation, and heat damage to the skin or nerves. Therefore, all RFA procedures are performed under sterile conditions, similar to an operation.

 

Please get in touch if you wish to have more information about ablation treatment of osteoid osteoma in our department, or if you wish to make an appointment for yourself or your child.

 

  • Contact:

Minimally Invasive Tumor Therapy (MITT)

Charité, Campus Virchow-Klinikum

Department of Radiology

Augustenburger Platz 1

13353 Berlin, Germany

Phone: +49 (0)30/450-557309

Fax: +49 (0)30/450-557947

minimal-invasive-ambulanz@charite.de oder mia@charite.de

 

Case Example

 

We saw a 7-year-old boy presenting with severe nightly pain in the right shin bone. An X-ray examination was performed and showed marked widening of the cortex (the outer layer of a bone) in the middle segment of the tibia (the larger of the 2 bones in the lower leg). The radiolucent center (nidus), which characterizes an osteoid osteoma, is just barely visible within the distended cortical segment (Figure 2). In this case, an additional computed tomography (CT) scan was obtained, which revealed the typical nidus and confirmed the suspicion of osteoid osteoma (Figure 3A).

 

The boy was referred to our department for thermal ablation of his symptomatic (painful) osteoid osteoma. The RFA procedure was performed under general anesthesia. First, a hole was drilled into the nidus of the tumor. Next, an RFA probe was inserted into the nidus (Figure 3B and 3C). Heat was applied for about ten minutes. An MR image obtained directly after the procedure shows that there is no residual tumor left in the ablated area, confirming adequate ablation of the boy’s osteoid osteoma (Figure 3D).

Thermal ablation was successful and resulted in complete and permanent relief of pain.

 

Figure 2: X-ray of an osteoid osteoma of the right tibia. There is thickening of the cortical bone layer of a longer segment of the tibia (arrows) with a just barely visible radiolucent nidus in the center of the thickened segment.

 

Figure 3: (A) Computed tomography (CT) scan shows a cross-section of the patient’s right lower leg with the osteoid osteoma. The tumor consists of a core or nidus (indicated by the arrow) and surrounding reactive bony outgrowth. (B,C) A tract is drilled into the center of the tumor (the arrow indicates the drill in B and the tract after removal of the drill in C) for insertion of the RFA probe. (D) The dark area (arrowheads) in the MR image obtained after treatment confirms that complete destruction of the tumor has been achieved.