Microwave Ablation (MWA) is a minimally invasive technique used to destroy tumours that cannot be removed by surgery. This procedure uses microwave radiation to generate intense heat that breaks down cancerous cells. MWA is generally used on smaller tumours, as surgery offers a greater risk. Microwave ablation is most often used to treat tumours in the liver.

It is a useful alternative to surgery, as ablation can be used for treating tumours in those who are too unwell to undergo surgery, or if the tumour is too close to major blood vessels or the gallbladder; as this would make surgery difficult. Microwave ablation is much less invasive than surgery and the treated person is able to recover from the effects of the procedure within a week.

Why microwaves?

Microwave radiation, a form of electromagnetic radiation, is electrical and magnetic energy that moves through the air. Most people recognize microwaves from their use in microwave ovens, where they rapidly heat food to high temperatures. This ability to generate intense heat makes this form of energy a good choice for ablation.

The microwave ablation system consists of three key components: the microwave generator, the power distribution system and the application antenna.1 The antenna is inserted into the body and is responsible for delivering microwave radiation directly into cancerous tissue, where it generates heat to destroy cancerous cells. 

Microwave ablation differs from other ablation techniques, such as radiofrequency ablation (RF), primarily in the type of energy used.  While MWA employs microwave radiation, RF ablation relies on direct current to generate heat. One significant limitation of RF ablation is that the treated tissue becomes less conductive as it is ablated, which restricts the size of the area that can be effectively treated. In contrast, MWA does not face this limitation, allowing for a more extensive and predictable ablation zone. Additionally, MWA typically achieves more effective results in a shorter procedure time compared to RF ablation.²

MWA is used primarily to treat tumours in the liver, lungs, kidneys, adrenal glands and bones. The technique works by using microwaves to generate extremely high temperatures, which cause the tumour cells to die and break down. To ensure that the entire tumour is destroyed, some surrounding healthy cells are also affected. The body then breaks down and repairs the damaged area, a process that it cannot perform on cancerous cells. This targeted destruction helps eliminate the tumour while minimizing harm to the surrounding healthy tissues.

Microwave ablation treatment

The procedure for MWA can be performed either under general anaesthetic, where the patient is fully asleep or under sedation with local anaesthesia to numb the area where the antenna will be inserted. The choice between these options depends on the location of the tumour, the patient's overall health, and the complexity of the procedure. General anaesthesia is typically used for more extensive procedures, while local anaesthesia with sedation may be sufficient for smaller, less invasive cases. During the procedure, ultrasound imaging or a CT scan is used to guide the needle precisely into the tumour, ensuring that the microwave energy is applied to the targeted tissue. Once the antenna is positioned correctly, the doctor will activate it, heating the tumour with microwave radiation and destroying it. This can take anywhere from 30 minutes to a few hours,  depending on the size and location of tumours. After treatment, most patients can leave the hospital by the very next day.³ 

Success and risk

Microwave ablation has a high success rate, with up to 97% of patients⁴ undergoing complete ablation, meaning the tumour is entirely destroyed. The procedure is also associated with a low risk of major complications, reported at just 2.8%, and the chance of death as a result of the procedure is extremely rare, at less than 0.1%.² 

Side-effects of microwave ablation

Like any other medical procedure, MWA is not without side effects or potential complications, the most common of these are as follows:

• Discomfort or mild pain at the site of the procedure, treated with painkillers.
• Flu-like symptoms for a few days, known as post-ablation syndrome. They can last up to a week and can be managed with medication.
• Damage to the surrounding area: other organs may be damaged by the heat, but this is rare as the doctor can be careful and has an image to guide them.
• Bleeding caused by the needle entering the organ is rare but can be dealt with by the doctor.³

Reports state that tumours occurred in 34.8% of patients treated with MWA.⁵ This could be due to a number of factors, such as incomplete ablation of the entire tumour or the potential spread of tumour cells through the needle puncture. Despite these challenges, MWA is considered a more effective method than other forms of ablation and is generally preferred as a less invasive method to treat tumours. While it has shown promising results, microwave ablation is a relatively new treatment, having been in use for only the past 20 years.

Due to studies and reports demonstrating its efficacy and safety, Microwave Ablation is seen as a better form of treatment than other versions of thermal ablation (RF) and a viable way to destroy tumours. In the future there is the possibility to refine MWA further and provide greater precision in combating tumours to directly ablate the tumour cells, this however is not in use yet.⁶ 

Summary

Microwave ablation is a procedure that uses microwave radiation to combat tumours by generating large amounts of heat that destroy tumour cells. This is used when surgery is not viable for the person, due to the positioning of the tumour or if they are too unwell to go through surgery. It is a less invasive method that resects the tumour through surgery.

An antenna (needle) that emits microwaves is inserted into the tumour, generates heat and causes ablation (destruction) of the tumour.

Microwave ablation is a newer, safer, more effective method of destroying tumours than other methods of thermal ablation that may be used. In the future microwave ablation may become more effective and targeted than it currently is, due to advancing technology and research.