The first time a cancer patient was treated with radiation was in 1896, a few days after Roentgen discovered x-rays. Ever since, tumors typically have been treated with radiation bombardment — a method that sometimes shrinks them, but just as often negatively impacts surrounding tissues and structures.

Today, intensity-modulated radiation therapy (IMRT) is finally resolving that dichotomy. With multileaf collimators (MLC) and 3D planning, IMRT delivers the highest possible radiation dose to tumors while sparing surrounding healthy tissues. More than a century after Roentgen’s breakthrough, IMRT is roaring onto the radiology scene, driven by patient demand for fewer side effects, longer life expectancy, and better quality of life.

IMRT is “one of the most important technical advances in RT since the advent of the medical linear accelerator,” said the International Journal of Radiation Oncology, Biology, and Physics. “3D-CRT/IMRT is not just an add-on to the current radiation oncology process; it represents a radical change … IMRT, when fully developed, will improve the overall efficiency with which external beam RT can be planned and delivered, and thus will potentially lower costs.”

IMRT utilizes pencil-sized beams of high-dosage radiation that are contoured to precisely target a tumor. It’s a souped-up version of 3D conformal radiation therapy (3D CRT), with the addition of inverse planning software that enables doctors to determine radiation dosage first, then compute optimum distribution. IMRT has been commercially available for five years, although experimentation with it has been going on since the 1950s. Until recently, the process was too problematical for clinical use because of the sheer complexity of dose planning, beam mapping, and treatment verification. However, the recent availability of powerful, relatively inexpensive computers, faster planning programs, and new reimbursement codes are causing the number of IMRT installations to more than double each year.

When St. Luke’s Cancer Center in Bethlehem, Pa., acquired an MLC accelerator in May of 2000, it estimated it was one of only 24 hospitals to own one. In 2001, the installed base of MDS Nordion (Ottawa, Ontario, Canada) IMRT systems was 10 worldwide, and the annual report of Varian Medical Systems (Palo Alto, Calif.) stated that its SmartBeam IMRT installations had grown from 40 in 2000 to 92 in 2001. To date, more than 160 sites worldwide are utilizing the technology.

Please refer to the October 2002 issue for the complete story. For information on article reprints, contact Martin St. Denis