Study Indicates That MammoSite Offers Significant Advantages Over Conventional Radiation Boost Therapy for Breast Cancer.

Business Editors/Health/Medical Writers

ALPHARETTA, Ga.--(BUSINESS WIRE)--May 17, 2004

Study results presented at the Annual Meeting of the American Brachytherapy Society in Barcelona, Spain, show that the MammoSite Radiation Therapy System (RTS) is potentially a more efficient way to deliver a boost of radiation to a breast tumor site following whole breast external beam radiation. In the study, researchers compared MammoSite to electron radiotherapy, currently the method most often used to deliver a boost of radiation. According to the results of a 2001 study published in the New England Journal of Medicine, an electron boost dose of radiation following a lumpectomy and whole breast external beam radiation is particularly important for high risk breast cancer patients, reducing local recurrence rates by 48% in women younger than 40.

In this clinical analysis, the median amount of targeted tissue that received the prescribed radiation dose was 37.6 percent for patients who received electron boost radiotherapy. With MammoSite, that coverage was improved to 100 percent, nearly a three-fold improvement. Patients who were treated with MammoSite also had a significantly smaller amount of healthy tissue exposed unnecessarily to radiation than patients who were treated with electron radiotherapy.

Developed by Proxima Therapeutics, Inc., MammoSite is the most widely used partial breast irradiation treatment in the world, and has been used as a primary therapy for thousands of women since its FDA clearance in May 2002. Partial breast irradiation is the emerging practice of delivering radiation only to the tissue where cancer is most likely to recur, minimizing exposure to healthy tissue. Doctors at hundreds of hospitals and radiation treatment facilities offer MammoSite to appropriate, early-stage patients, allowing them to benefit from a site-specific treatment delivered in only five days.

"The advantage of administering a boost of radiation therapy is that higher doses of radiation can safely be delivered to the tissue surrounding the tumor site following a course of whole-breast external beam radiation," said Bradley Prestige, MD, radiation oncologist at Cancer Therapy Research Center in San Antonio. "The study results indicate that the targeted manner in which MammoSite delivers radiation to the tumor site makes it an optimal choice for delivering a boost of radiation to breast cancer patients. Additionally, the boost therapy can be completed in 1 day vs. 5 days for electron radiotherapy."

"These study results demonstrate the high degree of precision and accuracy that MammoSite provides as a boost treatment compared to electron radiotherapy," said Tim Patrick, president and chief executive officer of Proxima Therapeutics, Inc. "When physicians believe that a boost of radiation is indicated for breast cancer patients following external beam radiation, we hope that this compelling data will encourage them to use MammoSite. This should expand the adoption of MammoSite beyond its already broadly accepted application as primary therapy for appropriate patients."

About MammoSite RTS

MammoSite RTS is a minimally invasive balloon catheter that is inserted into the cavity created by a lumpectomy. During a five-day course of therapy, a tiny radioactive seed attached to a wire is inserted into the balloon, delivering prescribed levels of radiation under precise computer control to the targeted tissue surrounding the cavity. No source of radiation remains in the patient's body between treatments or after the final procedure. The American Society of Breast Surgeons is currently managing a MammoSite Patient Registry that now includes more than 1,000 patients. Safety and performance of MammoSite for delivery of internal radiation were evaluated in a multi-center study, which involved women with early-stage breast cancer. The results of the study were published in the International Journal of Radiation Oncology*Biology*Physics (February 2003). For a list of current treatment centers, refer to www.mammosite.com.

About Proxima Therapeutics

Based in Alpharetta, Ga., Proxima Therapeutics, Inc. is a privately held medical device company established in 1995 to develop site-specific cancer treatment systems for breast and brain tumors. Products include GliaSite RTS for brain cancer and MammoSite RTS for breast cancer. Additional information is available on the company's Web site at www.mammosite.com. Physicians and patients may call 1-86-MAMMOSITE (1-866-266-6748) for more information.