The clinical use of ionizing radiation is a complex process involving trained personnel who carry out a variety of interrelated activities.
- Clinical Evaluation
The initial evaluation of the patient includes history, physical examination, review of pertinent diagnostic studies and reports, and communication with the referring physician and other appropriate physicians involved in the patient's care. The extent of the tumor must be determined and recorded for staging; this will facilitate treatment decisions, determine prognosis, and allow a comparison of treatment results.
- Establishing Treatment Goals
The goal of treatment (curative, palliative, adjuvant, or to establish local tumor control) should be defined as clearly as possible. Treatment options with their relative merits and risks should be discussed with the patient. A summary of the consultation should be communicated to the referring physician.
- Informed Consent
Prior to simulation and treatment, informed consent must be obtained and documented.
- Treatment Planning
The cognitive process of treatment planning requires the radiation oncologist to have knowledge of the natural history of the tumor to be treated and to determine the tumor site, its extent, and its relationship with adjacent normal tissues. This process is based on consideration of the history, physical examination, endoscopy, diagnostic imaging, findings at surgery, and histology.
When ionizing radiation is to be used, the radiation oncologist must select beam characteristics and/or radionuclide sources, method of delivery, doses, and sequencing with other treatments. The sequencing with other treatments should be coordinated in collaboration with medical and surgical oncologists. The radiation oncologist determines the dose to be delivered to the tumor, limiting doses to critical structures, and the fractionation desired. Using these parameters, the radiation oncologist directs the medical physicist and dosimetrist in the design of potential treatment programs or develops them personally. This usually requires the acquisition of patient data, such as dimensions, contours, and cross-sectional images. Beam-specific physical data are used with source data and other physical characteristics measured by the physicist to calculate the dose to a specific point within the patient or to calculate the dose distribution within a region of interest.
The radiation oncologist, in consultation with the medical physicist and dosimetrist, selects the treatment plan. The radiation oncologist prescribes the radiation treatment course. The prescription should include: volume (site) to be treated, description of portals (anteroposterior [AP], posteroanterior [PA], lateral, etc.), radiation modality, dose per fraction, number of fractions per day, number of fractions per week, total number of fractions, total tumor dose, and prescription point or isodose. The prescription shall be signed by the radiation oncologist prior to the initiation of radiation therapy. The graphical isodose plan, when warranted, should be signed within one week of initiation of treatment.
Daily treatments are carried out by the radiation therapist following the prescription and treatment plan of the radiation oncologist. It is essential that all treatment parameters be described in detail and orders be signed by the responsible radiation oncologist. Likewise, any changes in the planned treatment by the radiation oncologist requiring adjustment in immobilization, new calculations, or even a new treatment plan, must be documented on the record and signed or initialed by the radiation oncologist.
- Simulation of Treatment
Simulation is the process of establishing and documenting the appropriate volume to be treated and identifying the normal structures within or adjacent to this volume. During simulation, optimal patient positioning is determined and treatment parameters are defined, including couch position, gantry angle, and collimator angle. Beam entry sites and other points helpful in patient positioning and field localization are identified on the patient. All field setups should be documented by properly labeled photographs and/or diagrams, and when appropriate, by standard radiographs or digitally reconstructed radiographs (DRRs).
- Fabrication of Treatment Aids
Devices to aid in positioning and immobilizing the patient, normal tissue shielding, compensating filters, etc., are to be used where appropriate.
- Physics
The medical physicist, dosimetrist, and radiation oncologist perform the calculations necessary to determine the appropriate dose to be delivered by the treatment equipment. This requires knowledge of the physical properties of the treatment units, whether external beam or radioactive implants. These calculations must be checked by an independent person or method before the first treatment if the total number of fractions is five or fewer, or otherwise before the third fraction.
- External Beam Treatment
External beam radiation therapy is usually delivered in single daily doses for several weeks or in multiple increments daily over the same period (hyperfractionation) or over shorter times (accelerated fractionation).
To permit proper delivery of therapy, radiographs or portal images produced by each treatment beam unit with the patient in the treatment position (portal localization films) are compared with the simulator films or digitally reconstructed radiographs to verify that the treatment beams and fields planned at simulation are well matched. When portal verification images can be made, they should be taken at least every 5 to 10 treatments and for any new fields. Dosimeters may be used, in vivo, to measure and record actual doses at specific anatomic sites.
- Patient Evaluation During Treatment
The radiation oncologist monitors the patient's progress, checks entries in the treatment chart, and discusses the plan of therapy and any changes with appropriate team members. Re-evaluation examinations of the patient should be performed at least weekly, or more often when warranted. Pertinent laboratory and imaging studies are periodically ordered and reviewed. The patient and/or referring physician should be informed of the progress of treatment whenever deemed appropriate. At completion of irradiation, the radiation oncologist should assess the tumor response and acute side effects.
- Follow-Up Evaluation
Periodically after treatment, assessment by the radiation oncologist of tumor response and sequelae of treatment is recommended. Early detection of post-treatment tumor progression may permit additional, potentially beneficial treatment. Early detection and treatment of radiation induced sequelae may avoid serious problems later.
- Brachytherapy
Brachytherapy, using radionuclide sources, may be used for many sites. The radiation oncologist selects the applicators and radionuclide sources. Implant localization radiographs are taken and computerized dose calculations performed. The radiation oncologist reviews these calculations and completes the prescription, which shall be signed and dated. This prescription should specify the radionuclide source and strength, the dose to clinically relevant points or minimum dose to the target volume, and the time course.
Other treatment modalities are sometimes combined with external photon beams or brachytherapy to enhance the antitumor effects and decrease the effects on surrounding normal tissues.
High-energy photon and electron beams, a computer-based treatment-planning system, simulation, dosimetry with direct participation of the medical physicist, brachytherapy, and the ability to fabricate treatment aids must be available to patients in all facilities, either on site or through arrangements with another center.
Continuing medical education programs should include the radiation oncologists and the physics, dosimetry, nursing, and radiation therapy staffs. The programs must cover the safe operation of facility equipment as appropriate to the individual's responsibility, and the treatment techniques and new developments in radiation oncology.
See the "Description of the Implementation Strategy" field, below.