Breast cancer’s cold war

Breast cancer detection has improved dramatically over the years. With mammograms and other imaging techniques, doctors can now spot tumors at their earliest stages. Yet invasive surgery is still necessary for even small cancers.

In a few years, that may not be the case. An experimental treatment may be able to eradicate small cancers without surgery, even stimulating the immune system to prevent recurrences.

The outpatient procedure, called cryoablation, freezes the tumors, killing cancerous cells without harming healthy tissue. Eventually, up to half of the 200,000 women who are diagnosed with breast cancer each year may be candidates for cryoablation, enabling them to avoid the trauma and disfigurement of conventional surgery.

“This method is potentially much better than current treatments,” says Dr. Michael S. Sabel, a surgical oncologist at the University of Michigan Comprehensive Cancer Center in Ann Arbor. “It’s less expensive, virtually pain free, doesn’t have the possible complications of surgery, and it gives an excellent cosmetic result because the breast maintains its normal shape.”

Normally, when women are diagnosed with early-stage breast cancer, their tumors are removed by lumpectomy, a surgical procedure requiring general anesthesia. Often, it leaves a cavity in the breast. Cryoablation, in contrast, doesn’t require a large incision and can be performed in a doctor’s office in less than an hour using only local anesthetic.

With the aid of ultrasound images, the physician guides a thin, needle-like probe through a small puncture in the breast until it penetrates the center of the tumor. Cold argon gas is pumped through the probe, causing an ice ball to form around the tumor. The ice is allowed to thaw, and the freeze-thaw cycle is repeated. Within a few weeks, the dead tissue is absorbed by the body’s immune system.

The process may even provide an added benefit. In mopping up the tumor, the immune system’s white blood cells are exposed to special proteins on the surface of the cancer cells. Scientists speculate that this might “train” the immune system to recognize the cancer cells as foreign invaders. This could provoke an immune response in which white blood cells destroy tumor cells should they recur or spread to other parts of the body.

“In studies on mice, freezing tumors increases the body’s immune response to cancer, but we don’t know yet if the same process occurs in humans,” Sabel says.

Still, results of a recent pilot study of 27 women with early-stage cancers were encouraging. One to four weeks after cryoablation, the women’s tumors were removed by lumpectomy and examined under a microscope to determine whether any live cells were left. Researchers found that the procedure destroyed all cancers less than 1 centimeter in diameter. It was also effective in women with tumors up to 1.5 centimeters who suffered from a type of cancer known as invasive ductal carcinoma.

“Hopefully, in the future, the lumpectomy won’t be necessary,” Sabel says, adding that a larger test should begin within the year.

The study also found that in tumors larger than 1.5 centimeters, there were still some live cancer cells around the ice ball in some patients, Sabel says. “It is possible that using more than one probe or moving the probe during freezing could be used to destroy larger tumors, but we haven’t looked at that yet.”

In the next decade, continued progress in breast cancer screening methods will mean that 40% to 50% of breast cancers will be diagnosed when they are less than 1 centimeter, says Dr. Helena Chang, a study coauthor and director of the Revlon/UCLA Breast Center of the Jonsson Comprehensive Cancer Center. This lends greater urgency to the search for less-invasive treatments.

“Cryoablation is an important first step,” she says.

*

(BEGIN TEXT OF INFOBOX)

Freezing tumors

Cryoablation, or cryosurgery, is used as an alternative to conventional surgery for some types of cancer and precancerous conditions. The technique is used to treat early-stage prostate, liver and skin cancers (both basal cell and squamous cell carcinomas); cancers that have spread to the liver; precancerous skin growths known as actinic keratosis; and abnormal lesions in the cervix.

“The trend now is to find ways to destroy tumor cells without using a surgical knife,” says Dr. S. Eva Singletary, a surgical oncologist at M.D. Anderson Cancer Center in Houston. “Cryosurgery is literally a Band-Aid surgery -- minimally invasive with minimal scarring.”