Radiation has been used to treat cancer for more than 100 years. In fact, the first cancer patient was treated in Chicago in January, 1896, less than one month after Roentgen’s discovery of X-rays. Millions of patients have undergone radiotherapy, and cure rates have increased steadily during this period. For some cancers radiotherapy is the first line of defense and for other types it is used in support of surgery, chemotherapy, or other treatments.   While the general technique — killing tumors with focused energy — is not new, radiation oncologists, medical physicists, and scientists are combining a number of modern technologies for producing significant breakthroughs in radiotherapy. One of the most exciting developments is called Intensity Modulated Radiotherapy or IMRT. IMRT uses computer-generated images to plan and then deliver even more tightly focused radiation beams to cancerous tumors than is possible with conventional radiotherapy. With this capability, clinicians can exquisitely "paint" a precise radiation dose to the shape and depth of the tumor, while significantly reducing the adverse effects of doses on healthy tissue. IMRT allows doctors to deliver substantially more cancer-killing energy (generally X-rays) to tumors while decreasing potentially harmful doses to surrounding healthy tissue. Clinical studies indicate that IMRT delivery combined with higher dose rates is resulting in significantly better patient outcomes. Published material reports that IMRT offers patients with diseases such as prostate cancer a 13 percent to 35 percent improved survival rate with a decrease in treatment side effects. IMRT helps radiation oncologists achieve this increased precision through a combination of computerized machines (called medical linear accelerators), that produce and deliver the radiation, advanced planning and control software, and specialized mechanical devices used to shape or "sculpt" the radiation beams. IMRT is the most advanced approach to what is known as 3D conformal radiation therapy, which has been in nationwide clinical trials involving thousands of patients at leading research institutions. The ultra-precise IMRT technique is demonstrating improvements in the treatment of prostate and head and neck cancers in studies underway at New York’s Memorial Sloan Kettering Cancer Center and Stanford University in California. About two dozen leading hospitals are delivering IMRT treatments (see: Hospitals That Provide IMRT Treatments), while many others are acquiring the necessary systems or software for their programs. In addition to prostate treatments, other trials are documenting IMRT’s effectiveness in treating head and neck tumors as well as breast cancer. How Does a Radiation Machine Work? Medical linear accelerators are the key systems used for delivering radiotherapy treatments. Standing approximately nine feet tall by nearly 15 feet long and weighing as much as 30,000 pounds, the accelerator consists of four major components: an electronics cabinet called a "stand," housing a microwave energy generating source; a rotating gantry containing the accelerator structure that rotates around the patient; an adjustable treatment couch; and operating electronics. Accelerators are located within specially constructed concrete treatment rooms to provide X-ray shielding. In operation, microwave energy, similar to that used in satellite television transmission, is used to accelerate electrons to nearly the speed of light (186,000 miles per second). They attain this velocity in a short distance, typically one meter or less. As they reach maximum speed they collide with a metal target, which in turn releases photons, or X-rays, with such energy they are measured in millions of volts (MV). Certain models can be switched so that the electrons bypass the target for direct electron therapy. This energy is measured in millions of electron volts (MeV). Radiation oncologists and physicists use electron or photon therapies for different types of cancer treatments. Generally speaking, photons (X-rays) are used for treating tumors deep within the body. Electrons, which cannot penetrate deep tissue, are used for more superficial disease including some skin cancers and shallow head and neck lesions. As the radiation strikes human tissue it produces (largely from naturally occurring water in the body) highly energized ions which are lethal to both normal and malignant cells. While both good and bad cells suffer from radiation, healthy cells can adapt over successive regenerative cycles. Malignant cells do not possess this adaptation mechanism and thus do not survive, a fact which generally dictates the practice of administering repeated radiation treatments rather than a single blockbuster dosage. IMRT: Advanced Conformal Therapy Cancer is most effectively treated when it is confined to its site of origin before the disease has spread. After it has spread, cancer is difficult to cure. Controlling the tumor when it is confined to its original site is called local control and is a prerequisite for cure. A fundamental tenet in radiation oncology is that local tumor control with radiation therapy increases by increasing the dosage level. Because of difficulties in precisely identifying the location of tumors using traditional radiation therapy planning methods, the target area was increased to include adjacent healthy tissue to ensure that the tumor was encompassed in its entirety. The dose given to the normal tissues determines the side effects of radiation treatment. In general, the tolerance of these healthy structures to radiation is somewhat less than the dose needed to eradicate a tumor. In order to avoid severe side effects, it is necessary to restrict the tumor dose to the tolerance level of the normal tissues. Three-dimensional conformal radiation therapy was the next method of high-precision radiotherapy. It arose with the emergence of modern diagnostic imaging techniques and high power computer workstations with advanced computer graphics. These tools enhance the ability to delineate the tumor target and normal structures through three-dimensional configuration of the tumor. This improves tumor coverage, allows for a much smaller dose to normal tissues by reducing the need for large safety margins, and decreases the side effects of treatment. This approach also permits the application of higher-than-normal radiation doses to the tumor itself, thus improving the probability of eradicating the tumor. Intensity modulated radiation therapy is an advanced form of three-dimensional conformal radiation therapy. With further refinements in radiation therapy treatment planning software and treatment delivery systems, the radiation oncologist now can specify the tumor dose and dose restrictions to normal tissues when designing the treatment. The treatment planning software allows the high dose radiation volume to be exquisitely shaped to the cancerous area and to be sculpted around normal organs, reducing the dose to these structures to minimal levels prescribed by the radiation oncologist. To deliver this treatment, a multileaf collimator in the head of the treatment machine is used to shape radiation beams. This computer-controlled mechanical device consists of up to 120 individually adjusted metal fingers or leaves. These leaves move across the radiated tissue while the beam is on, blocking out certain areas and acting as filters to vary the beam intensity to achieve the desired distribution of radiation dosage. This approach allows even higher, more effective, radiation doses to be delivered to tumors without increasing the side effects of treatment. Varian Medical Systems Products For IMRT Treatments Varian Medical Systems provides a complete suite of integrated hardware, software, and support services for IMRT treatments. Product offerings include: Image acquisition software – For linking diagnostic images such as CT scans into the treatment planning process. Treatment planning software – Used to plan the radiation dose delivered to the tumor and to "sculpt" the radiation beam to avoid surround healthy tissue. Ximatron treatment simulators – Instead of delivering therapeutic radiation doses, simulators take lower energy diagnostic quality X-ray images of the tumor in relation to neighboring healthy tissue. This localizes the tumor and allows the medical staff to plot a detailed blueprint for treatment. Clinac® medical linear accelerators – Used for delivering therapeutic radiation doses to the diseased site. Dynamic multileaf collimators – For shaping the radiation beam to conform to the 3D volume of the tumor. Treatment verification systems – Imaging hardware and software used to determine if the desired prescription is being delivered. Radiotherapy department information systems – For managing a patient’s complete cancer care regimen — from scheduling through treatment through billing. Respiratory Gating system - A System designed to define appropriate treatment beam-on times to synch with the patient*s breathing patterns allowing increased confidence in defining margins for conformal and IMRT treatments. Varian Medical Systems, Inc., (NYSE: VAR) is the world’s leading manufacturer of integrated cancer therapy systems. More than 4,200 Varian Clinac® medical linear accelerators and Ximatron® simulators systems are in service around the world, treating an estimated 100,000 cancer patients per day. The company is also the premier supplier of x-ray tubes for diagnostic imaging applications. Varian Medical Systems is involved in several high-growth product development opportunities, including its advanced brachytherapy system for cancer treatment and the world’s first real-time, digital X-ray fluoroscopic imager. In addition, the company is pursuing technologies and products that promise to improve disease management by employing targeted energy to enhance the effectiveness of leading-edge molecular medicine. Varian Medical Systems employs over 2,000 people who are located at manufacturing sites in North America and Europe and in its 34 sales and support offices around the world. In its most recent fiscal year ended October 1, 1999, Varian Medical Systems reported sales of $590 million.