Heat, cold KO cancer tumor, pain

CHICAGO, Nov. 29 (UPI) -- Intense pain caused when cancer spreads to bones can be controlled or eradicated by new image-guided treatments with laser energy that heats up the tumor and kills it or by super cold gas that turns it into a mini iceball, researchers said Thursday.

Both treatments quelled the bone pain -- considered by many patients as the most feared consequence of progressive cancer -- and also destroyed the tumor.

"These methods of killing tumors are both effective," said Dr. Stuart Silverman, associate professor of radiology at Harvard Medical School/Brigham and Women's Hospital in Boston.

"We do these procedures because of pain," Silverman said, although the procedures may also help control the cancer in some patients.

In one study presented in Chicago at the annual meeting of the Radiological Society of North America, Dr. Christian Stroszczynski, a researcher in radiology at Humboldt University in Berlin, said doctors using computer tomography and magnetic resonance imaging were able to position a laser at the site of bone metastases in 16 patients.

When activated for 15 minutes, the laser-induced thermotherapy heated the tumors to the point the cancerous tissues were ablated -- destroyed. The temperature was monitored during the procedure.

An MRI surveyed the effects of the treatment. The procedure took about an hour to perform. Older patients were able to undergo the operation while receiving just local anesthesia. Children required general anesthesia, Stroszczynski said.

He has continued to follow the progress of the patients for as long as 21 months after the initial surgery in March 2000. He reported that the procedure appeared to provide complete relief of pain in at least 12 of the 16 patients.

"Laser-induced thermotherapy is a promising method for minimal invasive ablation of bone tumors," he said.

In a second presentation, Dr. Sridhar Sankar, a clinical fellow in magnetic resonance imaging at Brigham and Women's Hospital, reported on treatment of eight patients with cryotherapy -- a procedure in which the tumor is frozen.

Using MRI technology, doctors placed a tiny hollow needle into the tumor. Through that needle technicians pumped pressurized argon gas that reached a temperature of minus 150 degrees Celsius, Sankar said.

"The cold gathers moisture from surrounding tissue, forming an iceball that encompasses the entire tumor -- killing it," he explained.

Silverman said by taking MRI scans every minute, doctors can actually watch as the iceball grows and can visualize when the tumor is encased in ice. The researchers freeze the tumor for 15 minutes, then let it thaw for 10 minutes and then re-freeze it, Sankar said.

Follow-up studies with the MRI demonstrated that the area of the tumor -- which once was bright in the MRI scans -- now failed to show any enhancement, an indication the tissue had been killed, he said.

Silverman said while laser heat and other methods of destroying the tumors are effective cancer killers, he prefers using the cryosurgery technique because the concurrent use of the MRI allows doctors to see what they are doing, eliminating guess work as to whether the procedure has succeeded in getting all the cancer.

Sankar said all the patients in the study got immediate relief of symptoms. Pain recurred in one patient six weeks later, in a second patient eight weeks later and in a third patient 12 weeks after the procedure. Some of the other patients have been pain-free for 18 months.

"This procedure may prove to be a viable alternative to surgery, chemotherapy or radiation for control of tumor growth or pain in some patients," Sankar said.

Although the treatments appear to destroy tumors, they are not curative, researchers said, since the bone metastases are indications that the disease has spread. At least one of the patients in the stduies died from progression of the disease.