An estimated 211,300 new cases of breast cancer are expected to occur among women in the United States during 2003, with about 81 percent of patients diagnosed when the disease is still in its early stage. Many early-stage patients still choose to have a mastectomy, but a growing number are opting for a less invasive course of treatment. This approach, called breast conservation therapy (BCT), usually involves tumor excision via lumpectomy, followed by six to seven weeks of external beam radiation therapy to reduce the likelihood of recurrence.

Although breast conservation therapy allows a woman to preserve her breast, up to 40 percent of patients with early-stage breast cancer still opt for a mastectomy, despite comparable long-term recurrence and survival rates (as reported in the New England Journal of Medicine, October 2002). Many of these patients decline breast-conserving lumpectomy because they are unable to sustain the time and travel burdens imposed by six to seven weeks of traditional external beam radiation therapy. According to National Cancer Institute data, an increasing number of those who opt for breast conservation therapy—about 25 percent—choose to forego any follow-up radiation treatment with the likelihood increasing the farther away a woman lives from a radiation treatment center. This is happening despite the fact that women who do not undergo radiation therapy following lumpectomy are known to be at a significantly increased risk of recurrence of the cancer.

Because of these trends and their concerning clinical implications, for more than a decade the medical community has been studying partial breast irradiation, an alternative method for delivering radiation therapy to breast cancer patients in just five days. The approach most rapidly gaining acceptance and usage across the country in accelerating the breast irradiation process is a technology known as brachytherapy. Brachytherapy involves the internal administration of radiation via “seeds” delivered directly to the tumor site. Brachytherapy has been used for many years for treating prostate cancer. Today, brachytherapy’s benefits are finally being applied to address unmet needs in breast cancer.

Leading the ascension of breast brachytherapy into the clinical mainstream and enabling the concept of accelerated partial breast irradiation to become a nationwide reality for patients and physicians is the MammoSite Radiation Therapy System (RTS). Proxima Therapeutics, Inc. has developed this brachytherapy device that internally administers a site-specific, prescribed dose of radiation to breast cancer patients in a five-day course of therapy.

Compared to conventional methods, MammoSite RTS represents a less invasive application of breast brachytherapy. Conventional approaches to breast brachytherapy require the insertion of 15 to 30 catheters per procedure, which is invasive to the patient and relatively complex for a physician to perform. In contrast, MammoSite RTS only requires a single catheter, making it more comfortable for the patient and easier for the physician to perform. As a result of these benefits, MammoSite RTS is bringing breast brachytherapy to more patients. With the extensive number of patients treated to date with MammoSite RTS and rapidly growing pool of physicians trained to perform the procedure, the adoption of MammoSite has already surpassed all other forms of accelerated partial breast irradiation (APBI) by a wide margin.

The U.S. Food and Drug Administration (FDA) cleared the MammoSite RTS for use in May 2002. Physicians and patients alike responded positively to the less invasive nature and short duration of APBI with MammoSite. Within a year of its FDA clearance, MammoSite RTS has become available in more than 200 centers and has been used to treat more than 1,500 women. Safety and performance of the device for the delivery of internal radiation were evaluated in a multi-center study, which involved women with early-stage breast cancer. Results of this study were published in the International Journal of Radiology*Biology*Physics (February 2003).

MammoSite RTS internally delivers radiation directly to the tissue surrounding the tumor cavity, minimizing radiation exposure to the rest of the breast, skin, ribs, lungs and heart. During the lumpectomy procedure or shortly thereafter, the deflated MammoSite balloon is placed inside the tumor resection cavity. The applicator shaft, a tube connected to the balloon, remains outside the breast. Once in place, the balloon is inflated with saline to fill the cavity, the catheter site is dressed, and the patient may go home. The balloon remains inflated for the entire time that the patient is receiving radiation therapy. The patient returns to the hospital for treatment on an outpatient basis where a radioactive “seed” is inserted within the inflated balloon, beginning what is typically a five-day sequence of treatments. No source of radiation remains in the patient’s body between treatments or after the final procedure. When the therapy is concluded, the balloon is deflated and the MammoSite RTS catheter is easily removed.

In its review of accelerated partial breast irradiation as a sole treatment modality following lumpectomy, the American Brachytherapy Society states that appropriate patient selection and quality assurance are “clearly critical components and necessary to assure successful treatment outcome.” The Society additionally states that "the ability to complete treatment in five days has the potential to provide additional women with the option of breast conservation." Internally administered radiation therapy is covered by most insurers. Specific coverage for the MammoSite RTS will depend on a patient’s individual health care plan. For up-to-date information regarding geographic availability of the MammoSite RTS, please visit www.mammosite.com or call 1-86-MAMMOSITE (1-866-266-6748).

This information is provided by Wake Radiology Oncology's Doctors, Nurses, and Technologists.  It was added to this site on November 12, 2003 and last updated on January 29, 2004.