MWA - Microwave Ablation

A needle heats a tumor to over 60 degrees and it dies in minutes. No incision, one night in hospital, and the same control as radiofrequency in a randomized trial.

Microwave ablation destroys a tumor from the inside with heat. An antenna the width of a knitting needle is guided into the lesion under ultrasound or CT. Microwaves agitate the water molecules around its tip. The tissue cooks to a set size within a few minutes. It treats liver, lung, kidney and thyroid lesions that are small enough to fit inside that zone, in patients who cannot or should not have surgery. In a randomized trial of liver cancer, 6 percent of lesions treated with microwaves had regrown at two years against 12 percent after radiofrequency, and no patient died of either treatment.

How microwave ablation works

Microwaves at 915 or 2450 megahertz, the same frequencies as a kitchen oven and a wireless router, make water molecules spin. Spinning molecules generate heat. In microwave ablation the source of the microwaves is the tip of a thin antenna placed inside the tumor, so the heat forms in the tissue itself instead of being conducted into it from a hot electrode, and that single difference from the older technique, radiofrequency ablation, gives microwaves three advantages. They heat a larger volume in less time. Charring does not stop them, whereas it stops an electrical current. Blood flowing through nearby vessels cools them less, so lesions next to large veins are treated more reliably. Tissue above 60 degrees dies at once. The radiologist plans the ablation zone to cover the tumor plus a margin of at least five millimeters of normal tissue, and the margin decides whether the treatment holds.

Organ by organ

Four organs account for nearly every procedure.

Liver

Ablation began in the liver, and the liver holds the strongest evidence. Guidelines for hepatocellular carcinoma recommend it as a curative treatment for tumors under three centimeters in patients who are not candidates for surgery or transplant, and as an alternative to surgery for the smallest ones. Metastases from bowel cancer get the same treatment when they are few and small, often together with chemotherapy or after a liver resection has removed the larger ones. The needle goes through the skin below the ribs under ultrasound. One session reaches lesions of three to four centimeters.

Lung

Lung metastases, and small primary lung cancers in patients who cannot have surgery, are treated under CT guidance with the patient lying on the table and the antenna passed between the ribs. Air changes the physics. It conducts heat poorly, so the lung insulates the ablation zone well and carries microwaves into it badly, and the results therefore depend on size and position more than in any other organ.

Kidney

Small kidney tumors under four centimeters, found by chance on a scan, are increasingly ablated and left in place, above all in older patients and in those with one kidney or poor kidney function, where preserving every part of the organ counts. A biopsy comes first. A quarter of such tumors turn out to be benign.

Thyroid

Benign thyroid nodules that press on the windpipe or show in the neck can be shrunk with a thin antenna under ultrasound in an outpatient session, and the nodule loses most of its volume over a year. Nothing else on this page treats a benign condition. Surgery, the alternative, removes half the gland.

What the studies found

Each study below is open. Close the ones you have read.

Who it suits

The consensus document on tumor ablation by Ahmed and colleagues defines technical success as an ablation zone that covers the tumor and its margin on the first scan afterward. Patient selection serves that definition. Four things have to be true.

1. The lesion is small enough. Three centimeters or less gives the most reliable result. Between three and five centimeters the zone may need two antennae or two sessions. Above five, ablation rarely clears the margin and other treatments come first.
2. There are few lesions. Up to three in the liver, and a handful in the lung, can be treated in one or two sessions. Beyond that, drugs or radiotherapy treat the organ as a whole.
3. The lesion can be reached and seen. A needle path that avoids bowel, gallbladder, large vessels and the diaphragm, and a lesion that shows on ultrasound or CT during the procedure. Lesions at the dome of the liver or beside the heart are the hardest.
4. Surgery is not the better choice. A fit patient with a single resectable liver tumor and no cirrhosis is offered surgery, which removes more tissue with a wider margin. Ablation is for patients who cannot have surgery, do not want it, or would lose too much organ to it.

Some patients wait. Blood thinners that cannot be stopped, an uncontrolled clotting disorder, a lesion less than a centimeter from a large bile duct or the bowel, and an active infection are reasons to postpone or to choose something else, and the radiologist says which.

The procedure

Risks and complications

Every organ has its own list.

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How it compares with the alternatives

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Days in Istanbul, cost and the trip

1. CT or MRI images with reports, and the pathology if a biopsy was done
2. Liver or kidney function, clotting tests and a recent blood count
3. The full medication list with blood thinners marked, and any allergy to contrast or sedation
4. The history of the cancer, with dates of surgery, chemotherapy and earlier ablations
5. Whether a companion will travel with you, and any request for a female doctor

Cost follows the number of lesions and sessions, the organ, the type of anesthesia, the imaging before and after, the antenna, which is a single-use device, and the night in hospital. Two antennae or two sessions for a large lesion double the device cost, more or less. Published packages in Istanbul cover the consultation, the ablation, anesthesia, one night, the follow-up scan, an interpreter and transfers. Hotel, flights, a PET-CT and any chemotherapy fall outside them, and your own health enters through the anesthesia plan and through liver or kidney function. A figure follows the radiologist's review of the images, which costs nothing. One coordinator handles the case in English, Arabic, French, Russian, Serbian, Romanian or Spanish, or through an interpreter, sends the appointment confirmation and an invitation letter naming the hospital and the treating doctor ten days before travel, and books the hotel and the transfers. The room has a companion bed. Halal, vegetarian and diabetic meals are available, a prayer room is on site, and a female doctor can be requested when you first write.

Results, and after you fly home

The first scan decides, and the second confirms

Complete ablation is judged on the CT or MRI taken within a day or a month, where the zone should cover the tumor with a margin. A scan at three months then separates a shrinking zone from regrowth at its edge, and scans continue every three to four months for two years, then every six. Regrowth at the edge is treated with a second ablation in most cases, and new lesions elsewhere in the organ are treated when found small. The consensus document by Ahmed and colleagues sets out this reporting and follow-up standard.

Microwave Ablation - MWA FAQ