Microwave Ablation - Uses, Advantages, and Disadvantages

Introduction:

The incidence of benign and malignant tumors is rising steadily. Despite various advances in oncology, their prognosis remains inferior if not treated meticulously. Though surgery remains the mainstay, cancer treatment is evolving periodically to employ minimally invasive novel techniques. One such revolution was the successful use of tumor ablation procedures, especially in inoperable tumors.

What Is Tumor Ablation?

Ablation is a minimally invasive procedure used to treat various tumors. They help destroy the tumor cells without having them surgically removed. Ablation can be effectively used to treat various tumors in the lungs, kidney, liver, breasts, uterus, prostate, thyroid, brain, and bone. This procedure uses computed tomography (CT) or magnetic resonance imaging (MRI) to precisely locate the tumor cells. Then, a small probe (needle) is inserted through the skin till it is in contact with the tumor cells. This probe is connected to a generator that produces certain energy to burn or freeze the tumor cells.

What Is the Significance of Ablation in Cancer Treatment?

Tumor ablation is considered an effective first-line therapeutic tool in small-sized tumors (less than 3 cm), especially in hepatocellular (liver) carcinoma or benign (non-cancerous) liver tumors. An ablation is a vital option in patients who have had unsuccessful chemotherapy or radiotherapy. They are also important in cancer patients who are not ideal candidates for surgical treatment. An ablation is a viable approach in advanced liver cancer patients waiting for a transplant. The advantage of ablation over conventional treatment modalities is that it is minimally invasive with easy recovery. However, ablation can destroy the normal tissues surrounding the tumor; hence it is not indicated in tumors near major blood vessels or any vital anatomical structures.

What Are the Different Types of Tumor Ablation?

Ablation can be broadly categorized into two types depending on whether the tumor cells are burned or frozen. They are described below:

1. Freezing Tumors: This type of ablation is also known as cryoablation. In this procedure, freezing gas is passed through the probe to freeze the tumor, which destroys the tumor cells.

2. Burning Tumors: In this procedure, extreme heat is used to burn the tumor cells. They are further categorized into microwave ablation and radiofrequency ablation. Microwave ablation uses electromagnetic waves to generate heat energy to destroy the tumor cells. In contrast, radiofrequency ablation uses high-frequency radio waves to generate heat and destroy the tumor cells.

3. Other Modes: Apart from heat and cold, laser, alcohol, and high-intensity focused ultrasound can also be used to destroy the tumor cells.

What Is Microwave Ablation?

Microwave ablation is a kind of heat ablation that is used to destroy tumor cells. It uses electromagnetic waves (microwaves) to produce heat. The energy produced due to the vibration between an electric field and a magnetic field is known as electromagnetic radiation. These electromagnetic waves cause the water molecules within the tissue to oscillate billions of times each second, resulting in heat production. This heat consequently destroys the tumor cells.

What Are the Common Uses of Microwave Ablation?

Microwave ablation is most commonly used to treat small-sized carcinomas that are surgically inoperable. They are used in various types of cancers, as mentioned below:

• Hepatocellular carcinoma (liver).

• Renal carcinoma (kidney).

• Lung cancer.

• Bone cancer.

• Metastatic carcinoma (cancer that has spread to other organs).

• When chemotherapy or radiotherapy has not proved successful.

• Patients in whom surgical intervention is not feasible due to their age or medical condition.

What Is the Difference Between Microwave Ablation and Radiofrequency Ablation?

The differences are mentioned below:

What Are the Advantages of Microwave Ablation?

Microwave ablation is considered far superior to radiofrequency ablation (RFA), a standard procedure for ablating various tumors. They are mentioned below:

• Microwave ablation is faster, more efficient, and faster than RFA in destroying tumor cells.

• Possibility of ablating multiple tumors simultaneously.

• Microwave ablation can ablate reasonably larger tumors when compared to RFA.

• Little or no pain associated with the procedure.

• Quick recovery.

• Image-guided procedure; hence it is more precise.

• Recurrence rates are considerably reduced.

• Minimally-invasive procedure.

What Are the Disadvantages of Microwave Ablation?

Though microwave ablation is highly efficient in ablating tumors, certain difficulties limit their widespread usage. They are given below:

• It is difficult to generate and safely deliver microwave energy.

• Technical difficulties include shaft heating (cable delivering the energy gets overly heated), more significant diameter probes, and the ablation zones being relatively thin and hence cannot be used in tiny bone lesions.

What Is the Principle Behind the Microwave Ablation of Tumors?

Microwave ablation uses electromagnetic waves to generate heat. These electromagnetic waves are produced in a generator, which is connected to the probe (needle) through some insulated cables (wires). The electromagnetic waves, once produced, are passed into the tissue through the probe. Within the tissue, these waves cause the tissue water molecules to oscillate at a very high speed. This oscillation, in turn, generates heat high enough to burn the tumor cells. This heat also closes tiny blood vessels, thus reducing the risk of bleeding. The burned tumor cells are later replaced by scar tissue. This entire procedure is done under the guidance of CT or MRI to locate the tumor tissue and guide the probe to the exact location.

What Are the Preparations Required Before the Procedure?

• Patients are advised to fast for six to eight hours before the procedure. However, they can take regular medicines with a few sips of water.

• Patients should inform the doctor of the list of medications they take, including supplements and over-the-counter medicines.

• Any history of allergy to anesthesia, contrast material, food, or medicines should be informed to the doctor.

• Ladies who are pregnant or might be pregnant should also inform the doctor.

• Patients on blood thinners and non-steroidal anti-inflammatory drugs need to stop these medicines a week before the procedure to avoid the risk of bleeding.

• Doctors may advise certain blood tests to determine the blood clotting time.

• The patient cannot drive back home after the procedure and will hence be required to have someone to help.

• Patients should wear loose, comfortable clothes and remove any jewelry or accessories before the procedure.

How Is Microwave Ablation Done?

• The patient will be required to change into a hospital gown and lie on the examination table.

• Microwave ablation is usually done on an outpatient basis.

• The vitals of the patient will be monitored.

• An I.V line (intravenous) will be secured on the arm of the patient, and sedatives will be given through the I.V.

• The site of probe insertion will be cleaned and sterilized with an antiseptic solution.

• If the patient is awake, a local anesthetic might be needed to numb the skin.

• A tiny cut will be made on the skin, and the needle will be inserted through it with the help of CT or MRI. The needle would be advanced till it reaches the tumor.

• Once the needle is in place, electromagnetic waves will be passed through the needle to generate heat and subsequently destroy the tumor cells.

• Larger tumors might needle multiple ablations by repositioning the same needle or using multiple needles.

• Once the procedure is complete, the needle will be removed, and pressure will be applied to stop any bleeding.

• A sterile bandage will be placed over the incision site.

• The I.V lines will be removed.

• A single ablation may take roughly around 30 minutes or more, depending on the site, size, and accessibility. The entire procedure may take two to three hours.

What Are the Instructions After the Procedure?

• After the procedure, the patient would be assisted to the recovery room.

• The patient will not be able to drive back home.

• They will be advised to rest for two to three days.

• They can resume their normal activity within a few days.

What Are the Benefits and Risks of the Procedure?

Benefits:

• Minimally invasive procedure and hence fewer complications, and the recovery are quick.

• Cost-effective when compared to other treatment options.

• It can be done adjunct to chemotherapy.

• The procedure is relatively quick.

• Highly successful in destroying smaller tumors.

Risks:

• Chances of infection.

• Thermal damage to the adjacent structures.

• Some patients might develop symptoms similar to flu three to five days after the procedure. This is known as a post-ablation syndrome.

• Excessive bleeding.

• Abscess formation.

Conclusion:

Tumor ablation is a vital procedure to treat various tumors, especially when other modalities have failed. Minimal invasiveness, efficiency, and precision have made tumor ablation clinically more relevant and a widely accepted mode of treatment in the field of oncology. However, further technical advances will be required to overcome certain limitations and make ablative treatments more constructive.