Technology and procedures for tumor ablation continue to evolve. Experts are evaluating new techniques for protecting organs, reducing pain, and avoiding complications.

Physicians can control the amount of pain their patients may experience by carefully evaluating the site of the tumor, the organ or structure being ablated, and the method used for ablation.

Where a lesion is located may be the key factor in how much pain tumor ablation will cause a patient. Lesions sited near the skin, diaphragm, or chest wall are particularly likely to cause serious distress.

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Pain caused by diaphragm burns is the most prevalent culprit behind prolonged hospitalization, according to Dr. Fred Lee, a professor of radiology at the University of Wisconsin Medical School. In fact, some patients describe postprocedural pain from burns to the chest wall as worse than surgical pain.

The easiest way to avoid pain is to remove the greatest risk factor: heat. Cryoablation may be the best method to use when pain is a significant factor. The inherent anesthetizing properties of freezing lead reduce pain during the procedure, and the patient's recovery is not hampered by painful burns. When confronted with a lesion in a particularly vulnerable location, such as near the chest wall or diaphragm, most experts recommend using cryoablation rather than a heat-ablation method.

Cryoablation may be the method of choice for treating painful bone tumors, said Dr. Matthew Callstrom of the Mayo Clinic in Rochester, MN. In some cases, pain from these tumors may diminish or disappear completely as soon as the freezing takes place. RFA, on the other hand, takes longer to eliminate the pain caused by these tumors, and the treatment itself can cause much more discomfort than cryoablation.

In some cases, physicians may choose to use general anesthesia during the ablation procedure. Dr. Eric vanSonnenberg, chair of radiology at St. Joseph's Hospital and Medical Center in Phoenix, said he tends to use general anesthesia when ablating lung tumors, especially those that are adjacent to the pleura. This can be particularly helpful when the physician needs to control or suspend the patient's breathing.

"We've had some cases where general anesthesia made a significant difference in being able to manage intraprocedural respiratory complications," vanSonnenberg said. "At times, we've found that to be helpful when we want to get into the lesion and the patient may not be totally cooperative. It's really touch and go getting exactly where you want to be."

To help control pain after the procedure, vanSonnenberg administers an intercostal nerve block.

Location of a lesion may also be the greatest factor in predicting major complications. The closer the area to be treated is to a vulnerable structure, the more likely it is for a complication to occur. Uretal stricture, for example, is one of the most common complications that can occur when treating lesions of the kidney. RFA-treated lesions that are medially located in the lower pole of the kidney are most vulnerable to causing strictures, said Dr. J. William Charboneau of the Mayo Clinic.

Much of this risk can be avoided by the choice of ablation method. Damage to adjacent structures is more common with heat-based ablation techniques than with cryoablation, said Dr. Damian Dupuy, a professor of diagnostic imaging at Brown Medical School. One benefit of cryoablation is that it is very easy to see exactly where the iceball is forming. This allows physicians to monitor how close they may be getting to a vulnerable structure and guard against stricture.

RFA or other heat-based ablation may be a good choice for lesions in the upper pole or the kidney or the liver but may not be ideal for poorly sited tumors. Charboneau recommends using cryoablation for any lesion located within 2 cm of the ureter, for example.

This does not mean RFA and other heat-based ablation methods should not be part of a physician's repertoire. Displacement techniques — such as using fluid, gas, or a physical barrier to move a vulnerable structure away from the area of ablation — can make RFA more practical even in tricky locations.

But the method of displacement can influence the potential for complications. Saline is a poor choice for displacement techniques, because it is highly conductive and can increase the area of the burn caused by RFA. Instead, experts recommend 5% dextrose(Drug information on dextrose) in water, a nonconductive liquid.

Even when these displacement techniques are used, physicians must keep a close eye on the structures around the ablation zone. Organs and structures shift during the procedure — for example, a nervous patient may swallow air, causing the colon to expand. What started out as a large margin of safety can diminish as the ablation proceeds.