This is a period of rapid developments in radiotherapy for malignant
disease. New methods of targeting tumors with computed tomography
(CT) virtual simulation, magnetic resonance imaging (MRI), and
positron-emission tomography (PET) fusion provide the clinician with
information heretofore unknown. Linear accelerators (linacs) with
multileaf collimation (MLC) have replaced lead-alloy blocks. Indeed,
new attachments to the linacs allow small, pencil beams of radiation to
be emitted as the linac gantry rotates around the patient, conforming to
three-dimensional (3D) targets as never before. Planning for these delivery
systems now takes the form of "inverse planning," with CT information
used to map targets and the structures to be avoided. In the
area of brachytherapy, techniques utilizing the 3D information provided
by the new imaging modalities have been perfected. Permanent
seed prostate implants and high-dose-rate (HDR) irradiation techniques
targeting bronchial, head and neck, biliary, gynecologic, and other
anatomic targets are now commonplace radiotherapy tools. CT-guided
permanent seed implants are being investigated, and a new method of
treating early breast cancer with HDR brachytherapy via a balloon
catheter placed in the lumpectomized cavity is coming to the forefront.
Newer modalities for the treatment of malignant and benign disease
using stereotactic systems and body radiosurgery are being developed.
Targeted radionuclides using microspheres that contain radioemitters
and other monoclonal antibody systems tagged with radioemitters have
been recently approved for use by the Food and Drug Administration.