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Varian® IX Linear Accelerator
Delivering radiation to the prostate externally remains a mainstay of therapy. There are several variations and technologies available to deliver External Beam Radiation. The Varian system represents an evolution of external beam radiation therapy and as such it and systems like it can be considered the gold standard of treatment.
Intensity-Modulated Radiation Therapy (IMRT) is the modification of standard external beam radiation therapy whereby the intensity of the radiation beam is computer controlled, or modulated, and is tailored to the three dimensional shape of the prostate or tumor. All radiation therapy machines in the Truckee Meadows use IMRT. The radiation dose intensity is elevated near the main tumor volume while radiation among the neighboring normal tissue is decreased or avoided completely. The customized radiation dose is intended to maximize tumor dose while protecting the surrounding normal tissue. To accomplish this, a MLC (multileaf collimator) is used. This is a computer-controlled system of thin metal blocks that shape and change the beam intensity relative to a specific point in a volume.
Image-Guided Radiation Therapy (IGRT) is the process of utilizing frequent two and three-dimensional imaging during a course of radiation treatment. Initially a radiation treatment plan is created based on imaging of the prostate. Using coordinates developed in this plan, imaging is used at each treatment to assure accurate delivery of radiation. At each treatment session, Calypso beacons are used to obtain real time accurate targeting of the prostate. There is no theoretical concern of daily CT scans leading to other cancers from the accumulated dose of radiation.
Treatment That’s Withstood the Test of Time
The backbone of all medical advances is scientific research, which utilizes randomized experimental trials to determine the effectiveness of treatment, optimize dosing, and minimize complications. The Radiation Therapy Oncology Group (RTOG) has largely carried out the major radiation therapy studies. These trials have set the benchmark for modern radiation therapy in prostate cancer. The results of these trials, which determine guidelines for radiation therapy treatments utilized in actual patients, are based on radiation therapy delivered with a linear accelerator like the Varian family of products. Of the external beam radiation therapies available in Truckee Meadows, the Varian system is the most established technology.
As you can see, the use of radiation therapy for prostate cancer is a complex topic. No single form of radiation therapy has been proven to be the best solution for all patients. When considering which treatment is appropriate for a given patient one must consider the characteristics of the cancer and the prostate itself (size, aggressiveness, anatomy) as well as the patient’s characteristics (age, health, current urinary, bowel and sexual status).