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
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,"
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
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
"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