Definition & Overview
Ablation therapy can be used to reduce or remove bone tumours. The procedure can be performed using heat energy, cold temperatures, or chemical agents. The heat is produced using microwave, radiofrequency, ultrasound, or laser. Cryoablation, on the other hand, is the procedure that uses extremely cold temperatures. The treatment is performed using advanced imaging technologies, such as computed tomography (CT) or magnetic resonance imaging (MRI).
Ablation therapy is one of the more recent developments in cancer treatment. It is non-surgical and minimally invasive. Its goal is to destroy tumours completely. If this is not possible, the volume or number of tumour cells is reduced as much as possible.
Ablation therapy is the treatment of choice for many types of bone tumours. This is because when compared to other bone tumour treatment options, ablation therapy:
- Is less invasive than surgical treatment options
- Has fewer risks and side effects compared to chemotherapy and radiotherapy
- Is targeted, which means only tumour cells are destroyed in the process. It does not destroy healthy tissue like chemotherapy does.
- Improves patients’ quality of life.
- Has minimal downtime. Patients can typically resume their normal activities after just a few days.
- Can be safely repeated if necessary
Who Should Undergo and Expected Results
Ablation therapy can be recommended for patients who suffer from malignant or benign tumours that grow on or have spread to the bones. These bone lesions typically produce various symptoms, including bone pain, fractures, and spinal cord compression.
A large percentage of bone tumours are malignant metastatic cancer that spread to the bones from somewhere else in the body. Bone metastases occur when cancer cells enter the bloodstream and reach the bone marrow.
Ablation therapy is effective for most types of bone tumours including osteoid osteomas, osteolytic metastatic lesions, and myeloma. The treatment is also effective for benign conditions, including giant cell tumour, chondroblastoma, and osteoblastoma. It destroys tumour cells, relieves symptoms (especially the excruciating pain associated with some bone tumours), and strengthens the bone.
The procedure is often used in cases where conventional treatment options have already been attempted without success. It is also sometimes combined with other treatment methods, such as cementoplasty.
The success of the procedure is influenced by several factors, including:
- The imaging technique used – In general, CT is the preferred imaging technology for ablation therapy for bone tumours. This is because CT is faster and can provide better resolution images of bone tissue.
- The approach route used – The goal of the procedure is to complete the treatment using the fewest possible sessions. Doctors also take care to avoid sensitive anatomic structures, such as nerves and blood vessels, as much as possible.
- The type of electrode used - For bone tumours, doctors generally use a rod electrode because it can be easily inserted through a drilled hole.
- The size and number of tumours – Larger tumours, as well as multiple tumours, are more difficult to eradicate compared to single and smaller tumours. This may thus have an effect on the goals of the procedure.
- Location of the tumour – Some tumours may be adjacent to flowing blood. This prevents doctors from delivering sufficient temperatures to destroy the tumour completely. Thus, the treatment may become limited to a partial destruction of the tumour.
How is the Procedure Performed?
Patients who are undergoing tumour ablation therapy for the reduction or eradication of one or more bone tumours will generally go through the following steps:
- The patient will undergo an assessment to obtain pertinent information about the tumour. These include:
- The number, location, and size of tumours
- The extent to which they have spread
- Based on such information, doctors will come up with an individual treatment plan for the patient. This will include:
- Appropriate size of the active electrode tip that will target the heat energy into the tumour
- The safest way to approach the lesion while avoiding nearby neurovascular structures
- During the actual procedure, the patient will be asked to lie down on a treatment table and will be placed under general anaesthesia or conscious sedation. Nerve blocks are also used when deemed necessary.
- The doctor will perform an imaging scan to obtain an image of the entire bone lesion and the selected approach route.
For radiofrequency ablation therapy using heat energy, the procedure is performed as follows:
- The doctor will place the active tip of the electrode on the treatment area.
- The doctor will administer the correct dose of heat energy or sound waves, which will pass through the tip of the electrode and into the tissue. Once it reaches the tumour, it will cause tumour cells to die.
For cryoablation therapy, the tumour is frozen, causing its cells to die. During the procedure, the doctor uses a cryoprobe that delivers argon gas into the tumour. The gas will result in rapid cooling. It can reach negative temperatures in just a few seconds.
After the procedure, patients will stay at the hospital for 24 to 48 hours. It is normal for them to experience some discomfort, fatigue, and muscle pain at the site where the ablation needle was inserted. The pain may be less for patients who have undergone cryoablation. Some patients may also get a low-grade fever. These symptoms occur a few days after the procedure. Once they go away, however, patients will experience a rapid recovery.
They are also given a follow-up schedule. During follow-up visits, the patient will undergo MRI scanning to check whether all tumour cells were destroyed or the treatment goals were met.
Possible Risks and Complications
Not all bone tumour patients can undergo ablation therapy. For example, the treatment is not recommended for patients who have cardiac pacemakers.
The treatment also has some potential risks and complications, including:
- Injury to nearby structures
- Abscess formation
- Skin and muscle burns
- Cartilage damage, especially when the treatment area is near the articular cartilage
- Weakening of the bone
Thermal damage to nerves
Santiago FR, Garcia MdMC, Montes JLM, Garcia MR, Fernandez JMT. “Treatment of bone tumours by radiofrequency thermal ablation.” Curr Rev Musculoskelet Med. 2009 Mar; 2(1): 43-50. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2684952/
Callstrom MR, Charboneau JW. “Percutaneous ablation: Safe, effective treatment of bone tumors.” Oncology Journal. 2005 Oct 1. http://www.cancernetwork.com/oncology-journal/percutaneous-ablation-safe-effective-treatment-bone-tumors