Brachytherapy Devices Reduce Postlumpectomy RT Time

CHICAGO—Brachytherapy devices that deliver radiation therapy directly to the lumpectomy site drastically reduce the time needed for radiotherapy after surgery for early-stage breast cancer, according to two studies presented at the 87th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).

The studies also suggest that the devices can decrease the amount of skin blistering and patient discomfort associated with conventional breast radiotherapy, improve the acceptance of the procedure for radiation oncologists, and provide excellent local control of disease.

A study (abstract 236) reported by Martin E. Keisch, MD, a radiation oncologist at Mt. Sinai Medical Center, Miami Beach, Florida, tested the MammoSite balloon breast brachytherapy applicator, which is being developed by Proxima Therapeutics, Alpharetta, Georgia, and has not yet been approved by the US Food and Drug Administration.

The study included 26 patients who were over 45 years of age and had T1N0M0 breast carcinomas of 1 cm in size, on average, with no evidence of microscopic disease on surgical margins.

The patients, who were treated with the MammoSite balloon breast brachytherapy device at nine centers, had only minimal complications. One patient developed an abscess with fluid collection that eventually resolved on its own. Radiotherapy-related side effects were mild; the most common were erythema, dry desquamation, and pain.

Although the study was not designed to evaluate local control of breast cancer, there has not been a single recurrence of breast cancer in a year of follow-up, Dr. Keisch said.

The other study (abstract 234) was presented by Euan Thompson, PhD, CEO and president of Photoelectron Corp., Lexington, Massachusetts, which markets the targeted intraoperative radiotherapy Intrabeam system.

"There is a growing feeling from practitioners involved in this and other studies that these devices may be sufficient to give a small, localized dose of radiation to a tumor area as opposed to treating the whole breast with conventional external beam radiotherapy," Dr. Thompson said.

A total of 25 patients with tumors ranging from 0.42 to 4 cm participated in Dr. Thompson’s study. The patients have been followed for a median of 29 months, and, in that time, there have been no major complications or breast cancer recurrences. The cosmetic results have ranged from good to excellent, he added.

MammoSite

The MammoSite device is a balloon that is filled with saline and inserted into the lumpectomy site at the time of surgery or later under ultrasound guidance. The balloon is placed in the lumpectomy cavity uninflated. Once in position, it is inflated with saline administered through a port to a diameter of 4 to 5 cm.

Over the next week, the patient receives a series of radiation treatments that are delivered through a remote afterload-er. The afterloader is a robot that gives a high dose of radiation to a small amount of breast tissue through a cable connected to the center of the breast balloon.

"By treating a smaller volume of tissue, we’re able to cut the treatment down from 6 weeks to 1 week," Dr. Keisch said. With conventional external radiation, he said, radiation oncologists treat the entire breast, and because treatment involves a large volume of tissue, radiotherapy is given slowly, typically over the course of 6 weeks.

When the dose of radiation is administered from within the breast device, the patient can receive 10 treatments (two treatments a day for 5 days). The dose of radiotherapy is the same as in conventional needle implantation—3,400 cGy—and it is given in 10 equal fractions. Each treatment lasts about 15 minutes, and it can be done under either local or general anesthesia.

With conventional breast radiotherapy, Dr. Keisch added, patients often develop some skin irritation, blistering, and discomfort that covers the entire breast. With the MammoSite device, the patients feel no sensation during treatment or afterward.

Dr. Keisch also noted that many radiation oncologists resist breast brachy-therapy using conventional approaches because the procedure is complex both in the placement of 10 to 15 needles in the breast and in computing the doses of radiotherapy. The MammoSite device, he said, is simple and safe to use, which may encourage radiation oncologists to adopt breast brachytherapy.

Intrabeam Approach

The Intrabeam approach is performed immediately after surgical removal of the breast lesion. "This technology allows you to place a source of radiation inside the tumor cavity as part of the surgery, using applicators that ensure a dose of radiation is uniformly applied to the inner surface of the cavity," Dr. Thompson said.

During the procedure, physicians place an applicator sphere in the lumpectomy site. There are five sizes of applicators, which have been designed to fill up the tumor cavity. An applicator that is slightly larger than the tumor cavity is selected and placed in the tumor site, and breast tissue is wrapped around it. A portable electron beam instrument delivers therapeutic radiation, ranging from 5 Gy to 20 Gy at 1 cm and 0.2 cm distance from the tumor bed, in 20 to 30 minutes.

"The technology that is used in this study is a small x-ray source," he said. The x-ray source contains miniature electrodes that generate low battery voltage of about 12 volts. "This power accelerates small-charge particles, which fire up a narrow tube under computer control and produce up to 50,000 volts at the tip of the needle," Dr. Thompson said.

Intrabeam, like the MammoSite, was designed to overcome problems with the current breast external beam irradiation approach, which requires a total of 30 hospital visits over a period of 6 weeks. Because of the need for so many hospital trips, women who live considerable distances away from major radiotherapy sites are deterred from receiving conservative breast cancer surgery and follow-up radiation therapy.

"A solution to these problems could be a nominal radiotherapy technique that will accurately deliver all the necessary radiotherapy in one sitting and treat only the index quadrant of the breast," Dr. Thompson said.

The Intrabeam procedure was developed in London, and it is being used in other areas of Europe, such as Heidelberg, Germany, as well as in Australia, Dr. Thompson said.

FDA Approval

The Intrabeam system has full FDA market clearance to deliver radiotherapy anywhere in the body. Some institutions, such as Children’s Memorial Hospital, Chicago, are using it to treat pediatric brain tumors.

In the breast, some hospitals in the United States are evaluating the technique primarily for administering a boost dose of radiation. "They are delivering whole-breast radiotherapy, and, in addition, they are delivering a dose of radiation using this device in the operating room to boost exposure in the tumor region," he said.

If proven effective in the management of early-stage breast cancer, Dr. Thompson believes Intrabeam could reduce the radiation oncologists’ workload by up to one third and allow breast cancer patients from remote areas to avail themselves of lumpectomy and radiation therapy."