Radiofrequency Ablation

Description
RFA of liver, lung and bone tumors

Preparation/Instructions
Pre-procedure workup

This is a method for treating some tumors using the concept of thermal ablation. We currently offer RFA of osteoid osteomas, other painful bone metastases, lung cancers and liver cancers.

What is RFA?

RFA is a technique that uses thermal ablation to "cook" lesions. Using an electrode and an RF generation adequate heat is generated inside a tumor, by placing the electrode within the tumor.

RFA is a well-validated technique for the treatment of liver and lung cancers, for the ablation of osteoid osteomas and for treating the pain associated with bone metastases. It has also been used for adrenal tumors as well as sporadically in other sites.

Procedure

1. We first assess the tumor in detail, using CT scans and MRI, which are performed at our centre. However, if these investigations have already been done, we go through them carefully.
2. If the lesion is suitable for an RFA procedure from the treatment perspective, we assess the technical feasibility.
3. If the lesion is technically accessible, then a pre-procedure work-up is performed, which consists of a basic health assessment, and the coagulation profile.
4. If there is no contraindication, the procedure is then performed under deep sedation, with an anesthetist in attendance.
5. The procedure for an osteoid osteoma takes upto 30-45 minutes. For all other tumors, it may take from 30mins to 2 hours depending on the size of the tumor.
6. After the procedure, the patient is observed in the post-procedure room, until he/she is fully conscious. Usually within three hours, the patient leaves our centre. The patient is allowed light food four hours after the procedure. The patient will be on oral antibiotic coverage for another 3 days.
7. With most tumors including osteoid osteomas, the patient can go back to sedentary, non-strenuous work within 24-48 hours.

Osteoid Osteoma

Points

1. Osteoid osteoma is a common benign bone tumor that occurs typically in the long bones
2. Traditional treatment involves surgery and en-bloc resection
3. Radiofrequency thermal ablation (RFA) can "cure" the lesion on an out-patient basis, using just deep sedation

An osteoid osteoma is a benign bone neoplasm that occurs typically in the long bones, such as the tibia or the fibula in about 50% of cases, in the diaphyseal or meta-diaphyseal cortex (Fig. 1). It is a relatively common neoplasm, representing about 12% of all primary bone neoplasms.

The typical age group is between 5 and 25 years of age (>75%) and more common in men. Patients with osteoid osteomas typically have pain, which become worse at night and which responds to anti-inflammatory drugs.

Radiologically, an osteoid osteoma has a typical appearance of cortical thickening and sclerosis. A nidus may not always be seen on plain radiographs, but will always be identified on CT (Fig. 1). On MRI, there is marrow edema with peri-osseous edema and usually the nidus is well visualized (Fig. 2).

Fig. 1 A	Fig. 1 B	Fig. 2

Fig. 1: (A, B): Osteoid osteoma. Plain radiograph (A) and CT (B) showing a typical meta-diaphyseal, cortical osteoid osteoma involving the upper end of the femur. The nidus is well seen (red arrow) with the surrounding cortical thickening (blue arrow).

Fig. 2: Osteoid osteoma. MRI shows the nidus (red arrow) along with marrow edema (blue arrow).

Traditionally, an osteoid osteoma has been treated with en-bloc resection and surgery. Though the results are good (85-95%), the complication rates are high, including fracture at the site of excision.

Among other alternative techniques is radiofrequency ablation (RFA). The principle of RFA is to induce thermal coagulation in the lesion and to "cook" the lesion to death. Cure rates with RFA are between 80-90%, with a 100% cure rate for a second sitting, if the lesion recurs. The complication rate is less than 2%.

The procedure is performed on an outpatient basis. After the lesion has been localized, deep sedation is given. A bone-biopsy trephine needle is inserted into the nidus. Through this needle, the RFA electrode is introduced (Figs. 3, 4). A temperature of approx. 100 degrees Celsius is applied for 3 minutes. If necessary, this cycle is repeated once more

Technical success is defined as the ability to put the RFA electrode into the nidus. Clinical success is defined as absence of pain after 24 hours following the procedure.

The patient is discharged the moment the effect of the anesthesia has worn-off and the patient has regained consciousness. A post-procedural course of antibiotics and anti-inflammatory drugs is prescribed.

On CT, there are no immediate signs of cure. In about 50% of patients, the lesion undergoes complete sclerosis at the end of six months, partial sclerosis in another 25% and no change in 25%. Therefore procedure success is purely measured on clinical grounds; i.e. disappearance of the typical pain associated with the lesion. On MRI, marrow edema is often seen around the site of ablation, demarcating the area of coagulation necrosis (Fig. 4C).

Fig:3 Osteoid osteoma of the femur. CT shows the position of the electrode within the nidus (red arrow).

Fig. 4 (A, B, C): Osteoid osteoma of the tibia. CT shows the position of the electrode (red arrow) within the nidus, in the axial (A) and longitudinal (B) planes. The post-procedure MRI shows the area of coagulation necrosis (red arrow) surrounding the nidus.

Cancers (lung, liver, kidney, painful bone metastases)

RFA is an excellent method of treatment for liver, lung and renal tumors.

In the lung, RFA is indicated in all situations where surgery would be indicated, but is not being performed due to either other co-morbid conditions that would make surgery risky or when the patient refuses. It is also performed when surgery is not the method of choice, to supplement radiotherapy or chemotherapy for associated metastatic disease.

For painful bone metastases, RFA helps in alleviating the pain. If the lesion is ablated in its entiretly, it may not recur. If it does, re-ablation can be performed as well.
In the liver, RFA is used in the treatment of hepatomas and metastatic disease and the results have been consistently good.

In the kidneys, RFA is again used for small tumors, where surgery is contraindicated, usually due to co-morbid conditions and survival is almost similar to surgery.