About one in three newly diagnosed cancer patients in the United States receives radiation treatment, which is being used increasingly as the first line of cancer therapy, according to Dr. Steven Leibel, president of the American Society for Therapeutic Radiology and Oncology (ASTRO).
He spoke at ASTRO's annual meeting, attended by several thousand worldwide cancer experts. ASTRO is the largest international organization of radiation oncologists.
Dr. Leibel, vice chairman and attending physician, Department of Radiation Oncology, New York's Memorial Sloan-Kettering Cancer Center, said that the use of radiotherapy translates into 450,000 patients this year.
Recent improvements in the precision of radiation therapy planning and delivery have demonstrated that higher doses of radiation are more effective in treating cancer with less toxic effect on healthy tissue, Dr. Leibel said. "This experience provides hope for immediate improvement in controlling local tumors," he added.
Long-term survival statistics compiled by the National Cancer Institute "indicate that approximately 65% of radiotherapy patients with a curative potential are indeed cured," Dr. Leibel noted. "Of those who fail, more than half initially relapse at local or local-regional sites." Evidence of a possible cause-and-effect association between local failure and an increased incidence of distant metastases underscores the importance of maximizing efforts to control cancer locally, he said.
Dr. Leibel also said, "Recent technological advances in computerized radiation treatment planning and delivery have produced new high-precision techniques to improve the likelihood of successful local treatment."
Computer technology and software design advances have provided "tools to aid in the ability to delineate the target and normal structures and to define more precisely the dose absorbed at each point within the irradiated tissues," Dr. Leibel explained.
Three-Dimensional Conformal Systems
Three-dimensional (3D) conformal systems generate treatment plans that focus the prescribed radiation dose at the tumor, conforming its distribution to the 3D configuration of the target. This reduces doses to normal tissues and enhances safety, Dr. Leibel said. "If 3D treatment planning and delivery are implemented at their technical feasibility and carried to the highest tolerable dose, the rates of local control hypothetically should increase, albeit up to a ceiling dictated by the inherent radiation resistance of each tumor type," he said.
Clinical use of 3D conformal radiation therapy (3D-CRT) is expanding rapidly worldwide, with systems in use at many institutions for routine patient management. Artificial intelligence and new image processing techniques are under development to address some of the limitations of 3D conformal systems. As for cost concerns, Dr. Leibel said many components of 3D-CRT are add-on costs to basic conventional radiation techniques, most of which are computer-driven and automated.
"Cost-benefit studies should include not only immediate cost parameters, but also the medical and socioeconomic impact of improved cure and the cost saving associated with decreased short- and long-term toxicity," he said.
Dr. Leibel added, "While significant advances have already improved the precision of radiation treatment and permitted close escalation, it remains for 'new biology' to match 'new physics' in this quest of local control ... As we turn into a new century, 3D in radiotherapy coupled with 'new biology' may indeed lead us into as yet unexplored dimensions in the ability to cure localized tumors."