Comfort lasts months, with option for further treatments as needed

October 1, 2002

Perhaps even more than death itself, many cancer patients fear spending their final months in excruciating pain. New research points to radio-frequency ablation as a source of fast and lasting relief that works when other methods of pain control fail.

Perhaps even more than death itself, many cancer patients fear spending their final months in excruciating pain. New research points to radio-frequency ablation as a source of fast and lasting relief that works when other methods of pain control fail.

A multicenter study from nine medical centers in the U.S. and Europe focusing on patients with metastases to the bone found that RF ablation successfully reduced pain in 95%. More than half reported relief within one week.

"All these patients had failed other modalities, including chemotherapy, radiation therapy, and even implantation of analgesic pumps in the intrathecal or epidural space, and they were having terrible pain," said Dr. Matthew Callstrom, an assistant professor of radiology at Mayo Medical School in Rochester, Minnesota. "We talked about where their most intense pain was and made sure we focused on treating that particular area."

The study garnered a Merit Award at the annual meeting of the American Society of Clinical Oncology, where the findings were reported in May.

A total of 43 patients participated in the study, each experiencing pain in no more than two sites of bone metastasis. With patients under general anesthesia, radiologists used CT or ultrasound guidance to direct a sheathed multipronged electrode to the surface of the bone at the site of metastasis. Once the needle was in place, they pulled the sheath back to release an electrode array that delivered RF energy to the soft tissue-bone interface, heating the area to 100 degrees C for at least five minutes-longer if the tumor was more vascular than expected. Their goal was to create about a 5-cm area of necrosis around the electrodes. Each procedure typically involved two to four needle placements, for a total procedure time of about one hour.

Researchers used a standardized questionnaire to measure the severity of pain before RF ablation and again one day after the procedure, weekly for one month, and then bimonthly. A clinically significant improvement in pain was defined as a two-unit drop on the pain scale.

Patients reported that the worst pain they had experienced in the preceding 24 hours dropped from a baseline average of 7.9 (on a scale of 1 to 10 ) to 4.4 at four weeks and 2.7 at 12 weeks. Both improvements were highly statistically significant (p

at week 12. By week four, patients reported that, on average, 70% of their pain was under control, compared with 43% at baseline.

Dr. William Charboneau, a professor of radiology at Mayo and the study's principal investigator, said RF ablation may relieve pain in three ways: First, it may destroy nerve endings at the edge of the tumor and in the bone. Second, RF energy shrinks the tumor, reducing the pressure it applies to adjacent bone. Third, a reduction in tumor volume may cut production of inflammatory cytokines, such as interleukins.

RF ablation is likely to be effective only in patients with focal sources of pain caused by osteolytic tumors that actively destroy bone. Sclerotic bone lesions, such those caused by metastatic prostate cancer, may be too hard to permit passage of the RF electrodes, according to Charboneau and Callstrom.

At least as important as how RF ablation works is how long lasting its effects are. Nearly all patients reported continued pain relief at six months, although two underwent a second procedure to control breakthrough pain. Seven patients died during follow-up for reasons unrelated to RF ablation. Their average pain score at the time of death was only 2.3.

"We were absolutely shocked at the duration of the effect," Charboneau said. "We thought if it lasted just a few months, it would be successful. In fact, the pain is not coming back even after six months for the majority of patients."

Long-lasting pain relief is an important benefit. Although many patients in the study were close to the end of their lives, others had slow-growing tumors and faced many years of intractable pain. Researchers have extended follow-up to two years in an attempt to determine how long pain relief lasts. They anticipate adjusting their approach to suit a variety of patients: increasing the number of focal lesions they treat to more than two, treating patients with slow-growing tumors more than once, and even doing the procedure in two stages for patients who have very large tumors.

This last approach has already offered dramatic relief to one patient with a large sacral tumor that was so painful he could not bear to sit down. Because the pain was only partially relieved following the first procedure, the patient underwent a second RF ablation of the remaining tumor one month later.

"He went from a pain level of 8 before the procedure to a 4 the next morning, and then, when we did the second treatment, to essentially a zero-from a situation where he couldn't sit to being able to sit," Dr. Charboneau said. "His quality of life was improved dramatically."