ROCKVILLE, Maryland—The FDA has approved the MammoSite Radiation Therapy System (Proxima Therapeutics, Alpharetta, Georgia), to deliver adjuvant radiation therapy after breast-conserving surgery for patients with early-stage disease. The device is designed to irradiate the surgical site with minimal exposure to surrounding tissue. It consists of a hollow catheter, to which an inflatable balloon is attached. After surgery, the device is implanted, the balloon inflated, and a radiation source is placed in the catheter. The balloon centers the radiation source at the wound site. After a series of treatments, generally extending over several days, the catheter is withdrawn.