BBI Contributing Writer
MONTREAL, Quebec — Patients with coronary artery disease (CAD) and those with prostate cancer have at least one expanding treatment option available — brachytherapy. This is a type of radiation therapy in which radioactive materials are placed in direct contact with the tissue being treated. Brachytherapy has been used in urology for years, but new delivery systems are improving the technique. Intravascular brachytherapy is a relatively new addition to the armamentarium of the cardiologist, radiation oncologist and medical physicist.
Brachytherapy techniques and their supporting imaging systems were featured in scientific presentations and exhibits at the American Association of Physicists in Medicine (AAPM; College Park, Maryland) annual meeting held here in mid-July. Formed in 1958, the AAPM membership includes 4,500 medical physicists and students.
Prostate cancer is one of the most common forms of cancer in men. It is the second-leading cause of male cancer deaths in the U.S. According to the American Urological Association (Baltimore, Maryland), most men do not die of this disease. Yet, prostate cancer still accounts for more than 30,000 American deaths annually, with 200,000 new cases a year and a one-in-six lifetime probability for acquiring the disease. Prostate cancer affects the cells of the prostate gland. The majority of the tumors are localized within the gland, making the disease vulnerable to localized radiation therapy.
Prostate brachytherapy is a procedure where radioactive seed implants are injected into the prostate. They deliver a higher dose of radiation than do external beams. During the implant procedure, between 100 and 200 rice-sized radioactive seeds are injected into the prostate under ultrasound guidance. The seeds may deliver one of several radioactive isotopes-including iodine and palladium-depending on the grade of the cancer. They do not have to be removed after they stop emitting radiation.
Mentor (Santa Barbara, California) provides practitioners with a wide variety of clinical support programs and products. These include a dosimetry preplanning program, patient education, treatment options and support groups — all on the company website. The company also distributes the SeedVue20 brachytherapy system for the Mick applicator and offers both palladium- and iodine-based seeds.
Varian Medical Systems (Palo Alto, California) provides both hardware and software to assist in brachytherapy procedures. Most recently, the company introduced the VariSeed Treatment Planning System. Image fusion allows CT data to MR for more accurate target identification, or CT to ultrasound for pre- and post-plan comparisons. The system's DICOM 3 interface allows acquisition of computed tomography, magnetic resonance imaging, ultrasound or other data over a network, or from another DICOM 3-compatible source.
Imagyn Medical Technologies (Irvine, California) offers the Isostar Iodine-125 interstitial seeds for brachytherapy. These seeds have high contrast under X-ray and fluoroscopy imaging. The isosleeve is used a sterilized custom pre-loaded needle delivery system, also from Imagyn.
Stenting of the coronary vessels after percutaneous coronary intervention (PCI) has improved on the limitations of angioplasty, acute vessel closure and restenosis by providing mechanical vascular support. Stenting has been widely adopted, but it is associated with a significant incidence of in-stent restenosis. Neointimal hyperplasia is the pathophysiologic process that leads to in-stent restenosis. Brachytherapy can be effective in reducing the occurrence of this process. Stents were placed in approximately 80% of the estimated 1 million PCI procedures in 2001 and about 150,000 cases of those patient experienced in-stent restenosis.
Beta and gamma isotopes are the two types of radiation currently used in brachytherapy delivery systems. Beta radiation emits electrons that penetrate only a few millimeters and requires two to five minutes for administration. Gamma radiation emits photons that penetrate tissues deeply. It is given for 15 to 20 minutes and provides almost uniform delivery to all blood vessel layers.
Using vascular brachytherapy for in-stent restenosis provides results of 14% to 34% restenosis rates following radiation compared with 32% to 72% restenosis rates seen with placebo. In-stent restenosis is documented using intravascular ultrasound, and intravascular brachytherapy is delivered via catheters with fluoroscopic guidance.
Novoste (Norcross, Georgia), the leader in the coronary brachytherapy sector, offers the Beta-Cath System, a proprietary catheter-based system which temporarily delivers a beta radiation source train hydraulically to the angioplasty site. Its design is similar to existing products used by clinicians and is easily adapted into the cath lab without requiring any special radiation shielding. The use of a beta isotope sets the Novoste Beta-Cath System apart by ensuring optimal performance while protecting the patient and healthcare providers from unnecessary radiation exposure.
Cordis (Miami Lakes, Florida), a Johnson & Johnson (New Brunswick, New Jersey) company, offers cardiologists the Checkmate Intravascular brachytherapy system. According to Cordis, this is the first and only intravascular brachytherapy system approved to treat longer lesions up to and including 45 mm. Results of three landmark studies confirm the efficacy of Ir-192 gamma radiation, documenting significant reductions in the incidence of in-stent restenosis, as well as a marked reduction in major adverse cardiac events in Ir-192-treated patients compared with placebo-treated patients. Pooled data from all three trials, looking specifically at native coronary arteries without new stent placement at the site of the lesion, showed patients treated with the Checkmate System had 66% fewer instances of in-lesion restenosis and 65% fewer major adverse cardiac events compare to patients assigned to placebo therapy.
Guidant (Indianapolis, Indiana) offers the Galileo Intravascular Radiotherapy System. The automated technology in this system allows the company to promote precision, time-saving quality assurance and clinician confidence. The system's integrated automation eliminates the need for manual calculation of radiation dose and dwell time while the proximal coded key connector automatically defines diameter and balloon length. The design of the system automatically centers the radioactive source within the arterial lumen; precise balloon positioning is enhanced by radiopaque markers.
Nucletron (Columbia, Maryland) offers the physicist and radiation oncologist an integrated imaging/therapy system to support increased workload and demand for fast, accurate treatment planning. Nucletron's IBU (integrated brachytherapy unit) allows fluoroscopy from all directions, intraoperative brachytherapy and verification of source position real time. The unit's ability to rotate enables unobstructed X-ray imaging from all possible directions without moving the patient.