Brachytherapy

by William M. Mendenhall, MD; Robert J. Amdur, MD; and Robert A. Zlotecki, MD, PhD

What is Brachytherapy?

Radioactive implantation has been employed since the discovery of radioactive isotopes such as radium.  Radioactive isotopes can either be placed directly into the tumor in the form of needles or seeds (interstitial brachytherapy) or into a body cavity (intracavitary brachytherapy).  Intracavitary radiation therapy is commonly used as part of the treatment for gynecologic cancers such as cancer of the cervix, whereas interstitial brachytherapy is often employed for squamous cell carcinoma of the head and neck and for adenocarcinoma of the prostate.

The advantage of brachytherapy compared with external-beam irradiation is that the dose falls off very rapidly. Only the tumor and a minimal amount of surrounding normal tissues receive the high dose of radiation therapy. The disadvantage is that if the size and location of the tumor are not precisely defined, the implant may underdose parts of the cancer.

Brachytherapy may be used alone in cases where the tumor is small and well defined, or to provide a boost dose in situations where the tumor is more advanced and/or ill defined. The treatment can either be given with low-dose-rate brachytherapy sources or, in some instances, with high-dose-rate brachytherapy. A variety of radioactive implants are employed at the University of Florida for malignant diseases as well as some benign conditions, such as endovascular brachytherapy to prevent restenosis of cardiac vessels after angioplasty.

Before any treatment is started, the recommended treatment, the reasons it is recommended, the procedures to be carried out, the expected or possible side effects or complications, and the expected benefits are all explained to the patient and family. The patient must give permission for treatment, based on this knowledge (“informed consent”), before treatment is given.

High-Dose Rate Brachytherapy

Brachytherapy is a method by which a radioactive source is placed in the part of the body that is to be treated and a high dose of radiation is given to a very limited area. The advantage of brachytherapy over external beam irradiation is that the dose is concentrated in a small area. The volume of tissue that is treated is limited, and the surrounding normal tissue receives a lower dose of radiation than it would if external beam irradiation was used instead. Brachytherapy can either be given with conventional low-dose sources, where the treatment takes place over several days in the hospital, or it can be given on an outpatient basis using a high-dose-rate (HDR) brachytherapy machine.

There is a long track record for use of low-dose-rate brachytherapy for a variety of tumors such as head and neck cancer, breast cancer, gynecologic cancer, and prostate cancer. HDR brachytherapy has also been used in these situations, but there is less experience with use of HDR brachytherapy compared with low-dose-rate brachytherapy. In some situations, however, HDR brachytherapy is as effective as low-dose-rate brachytherapy and has a very low risk of radiation injury. In these instances, it may be preferable to the low dose treatment because HDR brachytherapy can be given in 2 or 3 outpatient treatments. The actual treatment delivery lasts about 5 to 10 minutes, while the overall visit to the radiation therapy department lasts 30 minutes to 1 hour, in contrast to a hospitalization that might take several days for low-dose-rate brachytherapy.

An HDR brachytherapy treatment generally involves a short visit to the radiation oncology department, where a device or holder is placed into the area to be treated. Thereafter, the device is connected to an HDR brachytherapy machine, and a small, but intense, radiation source (a radioactive “seed”) is loaded into it. A high dose of radiation is given over treatment time that varies somewhere in the range of 5 to 10 minutes, depending on the intensity of the source. The radioactive seed is then withdrawn back into the brachytherapy machine, which then is disconnected from the device that was placed into the tumor.  The device is removed and the patient is discharged from the department to return a week or two later for a second or third treatment, depending on the number of treatments prescribed.

The advantages of HDR brachytherapy compared with low-dose-rate treatment are that it is more convenient and less expensive. An additional advantage is that there is minimal, if any, associated risk of deep vein thrombosis or thrombophlebitis, which may occur if a patient is placed in bed for several days for a procedure such as a low-dose-rate gynecologic implant.

Brachytherapy for…

Gynecologic Cancers

Internal implantation radiotherapy has been used to treat cancers of the vagina, cervix, and endometrium (the lining of the uterus) for many years. One of the reasons the cure rate of these gynecologic cancers is high, compared with similar-sized cancers in other parts of the body, is that the location and growth pattern of many gynecologic cancers make them suitable for treatment with internal implantation radiotherapy. The basic approaches that are used to deliver internal implantation radiotherapy for gynecologic cancer at the University of Florida are described in this section. It is important to remember that internal implantation is only one technique for giving radiotherapy. To understand when internal implantation is used in addition to external beam radiotherapy, go to site on treatment of gynecologic cancer.

Cervical Cancer

For cancers of the uterine cervix, internal implantation is usually performed after 4 to 6 weeks of external beam radiotherapy. The goal of external beam treatments is to shrink the tumor and eliminate any cancer cells that have spread to the pelvic lymph nodes. After external beam radiotherapy is completed, internal implantation for cervix cancer is most commonly done with a device called a “tandem and ovoid” applicator. A tandem and ovoid applicator consists of a hollow metal tube (the tandem) that is inserted through the cervix into the endometrial cavity (the central cavity in the uterus). The tandem is about 10 inches long and as thin as a pencil. The ovoids are hollow metal capsules that are small enough to fit in the vagina, up against the cervix.

The tandem and ovoid applicator is inserted under anesthesia in an operating room. The tandem and ovoid internal implantation procedure takes about 30 minutes. After the procedure the patient goes to a private hospital room. Radiation therapy is given through the tandem and ovoid applicator by placing radioactive capsules inside the hollow portions of the applicator. Placement of the radioactive capsules does not cause discomfort. The length of time that a patient has to remain in the hospital with the tandem and ovoid applicator in place depends on the situation. In most cases the applicator stays in for 40 to 48 hours. Instructions for patients who will be treated for cervix cancer with internal implantation are described in more detail in “A Radiation Therapy Implant for Cervix Cancer,” an informative brochure given to patients who will be having this treatment.

Endometrial Cancer

When radiotherapy is given for patients with cancer of the endometrium (the lining of the uterus), it is usually given after a hysterectomy. Radiotherapy is usually given with both external beam irradiation and internal implantation. Most patients receive three separate internal implantation treatments, separated by a week. The goal of internal implantation in this setting is to deliver a boost dose of radiation to the tissues near the upper part of the vagina. This kind of internal implantation radiotherapy is done in a special room in the radiation oncology clinic. The procedure begins by positioning the patient on a her back on a comfortable bed. A plastic applicator is placed in the vagina. The applicator is fitted to the vagina so there is little discomfort. Anesthesia is not needed. Radiation therapy is delivered with a machine (called a high-dose-rate brachytherapy machine that inserts a radioactive wire into the plastic applicator. The patient does not feel the radioactive wire go into the applicator. Radiation treatments are completed in about 15 minutes. The entire internal implantation session takes about 45 minutes. Hospitalization is not required for this type of internal implantation radiotherapy.

Vaginal Cancer

Radiotherapy for vaginal cancer is usually given with a combination of external beam irradiation and internal implantation radiotherapy. Unlike the technique of internal implantation described in the above section on endometrial cancer, internal implantation for vaginal cancer is usually done in an operating room with the patient under anesthesia. Usually, plastic needles are inserted into the tissues involved with cancer. Radiation therapy is given by placing radioactive wires inside the plastic needles. After the implantation procedure the patient stays in a private hospital room for about 48 hours with the implant and radioactive wires in position. Most patients have little discomfort during their hospital stay. The implant is removed in the patient’s hospital room. Implant removal takes about 5 minutes. The patient is discharged home from the hospital a few hours after the implant is removed.

Head and Neck Cancer

Radioactive implantation for head and neck cancer is usually in the form of interstitial low-dose-rate brachytherapy.  It may be used alone for early-stage cancers in accessible locations such as the mouth (oral cavity), lip, or nose.  For larger cancers, it may be combined with external radiation treatments. In these cases, the interstitial implant is used as a boost dose to the area of bulkiest disease.

Before any treatment is started, the recommended treatment, the reasons it is recommended, the procedures to be carried out, the expected or possible side effects or complications, and the expected benefits are all explained to the patient and family. The patient must give permission for treatment, based on this knowledge (“informed consent”), before treatment is given.

Implantation takes place in the hospital, with a brief period of anesthesia, and necessitates a hospital stay of several days. The implant is usually performed by placing hollow, stainless steel needles directly into the tumor and then “afterloading” radioactive iridium—that is, placing the radioactive material into the needles in the patient’s hospital room, after x-rays confirm the exact location of the needles and dose calculations are rechecked.

The results of brachytherapy are excellent for early-stage cancers of the head and neck.  The advantage of the radioactive implant compared with external-beam irradiation is the ability to limit the high doses of radiation to the tumor with minimal irradiation of the surrounding normal tissues. This is especially important for treatment of cancers of the oral tongue, floor of the mouth, lip, and nasal vestibule.

Prostate Cancer

Internal implantation radiotherapy is frequently used to treat patients with prostate cancer. By placing radioactive pellets (commonly called “seeds”) into prostate tissue, a high dose of radiation is given to the cancer with relative sparing of adjacent normal tissues like the bladder and rectum.

At the University of Florida, prostate seed implantation is performed in an operating room by a team of physicians and technical support staff who are specialized in performing the procedure. The radioactive isotope used to make the seeds radioactive is called iodine-125. A prostate seed implant is a permanent implant, meaning that the seeds stay in the prostate forever.

Seeds are inserted into the prostate by placing a series of needles through the skin between the testicles and anus. Anesthesia is used so the patient feels no discomfort during the procedure. A combination of transrectal ultrasound and x-ray fluoroscopy is used to guide seed placement. A seed implant procedure takes about 1.5 hours.

After leaving the operating room the patient spends one night in the hospital. Most patients are sent home the morning after the procedure.

The main side-effect of a prostate seed implant is irritation with urination. Patients often report that they have to urinate frequently and they have to get to the bathroom right away after feeling the urge to urinate. The symptoms usually go away after 4-6 months.