Afterloading radiation therapy
Afterloading radiation therapy, also known as high-dose-rate (HDR) remote brachytherapy, is a specialized form of internal radiation therapy that delivers targeted radiation directly to tumors using a computer-controlled device known as an afterloader. This technique employs a radioactive source, typically Iridium-192, which emits high-energy gamma rays, to treat a variety of cancers, including lung, breast, prostate, and cervical cancers. Afterloading therapy is considered a temporary implant, as the radioactive source is not left in the patient after treatment is completed.
This therapy is often performed after surgical tumor removal and is designed to provide precise dose delivery, minimizing exposure to surrounding healthy tissues. Treatment is generally quicker than traditional external beam radiation therapy, often requiring only one week of sessions compared to four to six weeks for external methods. Patients are carefully prepared for the procedure, which may involve catheter placement either during initial surgery or in an outpatient setting.
The afterloading process involves attaching catheters to the afterloader, with healthcare personnel monitoring the treatment from a separate room. After completing treatment, catheters are removed, and patients may experience minimal side effects. While risks exist, such as catheter movement and the possibility of radiation burns, overall success rates for HDR treatments are comparable to other cancer treatment modalities.
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Afterloading radiation therapy
ALSO KNOWN AS: High-dose-rate remote afterloading (HDR), temporary brachytherapy, and internal radiation therapy
DEFINITION: Afterloading radiation therapy is a form of high-dose-rate (HDR) remote brachytherapy that uses a computer-controlled machine called an afterloader to deliver radiation directly to a tumor. Iridium-192, a radioactive source that emits high-energy gamma rays, is a commonly used source of radiation in radiation therapy. The radioactive source is contained in the lead-shielded machine, which protects oncologists and other healthcare workers and is welded to a stainless steel cable that is inserted into the tumor through catheters, needles, or balloons placed in the tumor or tumor bed. Afterloading radiation therapy is considered a temporary implant because the radioactive source does not remain in the patient.
Cancers treated: Lung cancer, breast cancer, prostate cancer, head and neck cancers, uterine cancer, cervical cancer, vaginal cancer, esophageal and bile duct cancers, soft-tissue sarcoma, skin cancer, rectal cancer, gallbladder cancer, eye cancer, others under study
Why performed: The use of a high-dose remote afterloader provides more targeted therapy to the tumor or the tumor bed after the bulk of the cancer is removed in surgery. The afterloader provides more accurate dose delivery to the target site and helps protect normal tissue. Its use also provides a shorter course of therapy of up to one week, as compared to external beam radiation therapy, which takes place over four to six weeks. The dose distribution is more even with fewer hot (overdose) spots or cold (underdose) spots. Side effects occur less often with HDR therapy.
Patient preparation: Depending on the type of cancer and its site, planning for the use of afterloading radiation therapy often begins before an initial surgery. The surgeon and the radiation oncologist will confer to decide if the catheters used in administering the radiation will be placed at the time of the initial surgery for the cancer or in an outpatient setting under local anesthesia or other sedation.
Imaging or radiology studies may be used to assist in treatment planning for the optimal radiation dose delivery to the tumor site and to verify the location of the catheters, especially if it has been a few weeks since their placement. A simulation is done to visualize the tumor or tumor site compared to adjacent organs and tissues using a computed tomography (CT) scan or X-ray. This procedure assists the radiation oncologist in planning the amount of dose that the afterloader will deliver. The simulation data are then loaded into a treatment-planning computer, which calculates the dose needed.
Steps of the procedure: The patient arrives in the radiation oncology center and may change into a gown prior to receiving treatment. For some treatments, needles may be placed prior to the treatment under local anesthesia. Upon entering the treatment room, the patient is assisted to a comfortable position allowing access to the ends of the catheters or needles. The treatment catheters or needles from the patient are attached to the transfer tubes from the afterloader. The treatment personnel leave the room but can observe the patient using closed-circuit television and an intercom for communication. The treatment data loaded into the HDR unit control the movement of the source into the patient and the time that the source remains at various stops along the catheters or needles in order to achieve the distribution of dose planned. The source is placed in the patient for a few minutes, but a single treatment may take up to one hour or more.
The complexity of the treatment, the site being treated, and the strength of the radioactive source will dictate the time involved. There are two main schedules for afterloading radiation therapysingle-dose, high-dose-rate brachytherapy (HDR-BT) and fraction schedules, which are typically administered in two to three sessions. The radiation oncologist will discuss the type of treatment and the number of treatments needed based on the disease, but treatment times vary from a few days to slightly more than a week.
After the procedure: Depending on the site being treated, the patient may need to stay in the hospital or may be allowed to go home between treatments. A bandage may be placed over the catheters. After all treatments are complete, the catheters are removed by clipping the sutures holding the catheters, and they are withdrawn. A small amount of bleeding may occur, but it is quickly controlled with direct pressure, and a bandage is applied over the site.
Risks: Risks are related to catheter movement out of the site being treated. It is important for patients to tell the radiation staff if a catheter seems to have moved or if it gets snagged on clothing or the bandage at any time. A misplaced catheter or needle may deliver radiation to normal tissues or organs, causing radiation burns. There is also a risk that cancer cells may be missed by the radiation.
Results: Outcomes vary by the disease being treated, but success rates for HDR treatments are generally comparable to other forms of treatment.
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