Minimally invasive methods help treat bening and malignant tumors

October 1, 2002

Evidence is accumulating that conservative surgery is a viable alternative to mastectomy for many women with breast tumors. Now techniques pioneered by interventional radiologists are being proposed as the next step toward reducing the invasiveness of treatment.

Evidence is accumulating that conservative surgery is a viable alternative to mastectomy for many women with breast tumors. Now techniques pioneered by interventional radiologists are being proposed as the next step toward reducing the invasiveness of treatment.

Overtreatment of breast cancer has become a significant issue in the past 20 years, according to Dr. Margaret Hall-Craggs, a consultant radiologist at the Middlesex Hospital in London. Organized breast screening programs have resulted in detection of much smaller tumors, for which conventional therapies may be unnecessary. And as the population ages, the number of older women who have breast cancer is increasing. Aggressive treatment strategies are questionable in those who may die of other causes.

"There is a background evolving that suggests we should be looking at lesser treatments, because the disease itself is changing," Hall-Craggs told delegates at the European Congress of Radiology meeting, held in March in Vienna. "If you can identify that group of patients where there is clearly overtreatment, that is the group of patients we should start to perform clinical studies on."

A range of therapeutic interventions are under investigation for both malignant and benign breast tumors, she said during a refresher course at the Vienna meeting. Current options include percutaneous excision, ablation therapies (interstitial laser photocoagulation, focused ultrasound, radio-frequency ablation, and cryotherapy), and interstitial radiotherapy. But practitioners who choose a minimally invasive approach instead of surgery must ensure that the entire tumor has been destroyed, she said.

"We have to achieve a tumor-free margin equivalent to that which the surgeons are achieving when they do an operation," she said. "And we must make sure that we do no more harm than an operation and we don't adversely affect the patient outcome."

Thermal treatments have attracted considerable attention in Europe and the U.S. Doctors at the Middlesex Hospital have been testing interstitial laser photocoagulation, in which laser light passed through an optical fiber heats and destroys the targeted tissue. The team opted for a semiconductor diode laser source because it is portable and can be plugged into a regular energy source, Hall-Craggs said.

All breast tumor ablations performed at the Middlesex have been done with local anesthesia and sedation. An 8-gauge needle, which is large enough to accommodate the optical fiber, is guided into the tumor using ultrasound or MRI. Chilling the patient's skin with water and ice and applying pads helps prevent burns. Despite the simplicity of the treatment, however, no large-scale studies of its efficacy have been conducted. The only available data relate to short-term success in treating small tumors in a few patients, Hall-Craggs said.

"What has been established is that ablation can be achieved in small tumors," she said. "But modeling treatment to conform to larger and irregular tumors is extremely difficult. There are no large outcome studies, so this is not a treatment that can yet be accepted as conventional in breast cancers."

The situation differs for benign disease, for which the issues are simpler. Patients with breast fibroadenomas routinely undergo laser treatment at the Middlesex Hospital. Four patients have also undergone interstitial radiotherapy, an emerging technique that allows radiotherapy to be delivered within the tumor itself. A 12-volt supply provides rapidly attenuating x-rays, which are transmitted to the tumor via the tip of a probe. High radiation levels are localized in the tumor, saving healthy tissue from irradiation. Shielding is relatively straightforward and the whole system is portable. The therapy should be suitable for elderly patients who are not candidates for surgery.

Optical methods of biopsy could combine well with interstitial techniques, offering rapid diagnoses immediately prior to intended treatment, she said. Elastic scattering of light through malignant tissue, for example, generates characteristic spectra that can be detected by computer. Hall-Craggs and her team would like to link such a system to their Mammotome so that the optical biopsy can be targeted accurately.

"The results with this system have been really encouraging," she said. "Out of 88 measurements that we have made in breast tumors, 16 showed malignant spectra, of which 15 were truly malignant and one false positive. That leaves us with very good sensitivities and specificities, equivalent to most imaging techniques."