Seed implantation with iodine-125 or palladium-103 seeds (brachytherapy) is a highly effective treatment for patients with cancer. Brachytherapy requires no surgical incision, offers patients a shorter recovery time, and has less chance of troubling side effects. For example, for prostate cancer, brachytherapy is an outpatient procedure and most patients go home the same day as their treatment. They can also return to their normal activities a few days after treatment. Seed implantation takes only 45 minutes to 1 hour. Seed implantation with iodine-125 seed gives a lower dose rate of radiation than palladium-103. Because iodine-125 works in your body longer than palladium-103, it is ideal for treating slow growing tumors such as most prostate cancers. The 125 iodine seeds-which have a half -life of 59 days-release a short-course of gamma ray. The seeds implanted into cancerous masses and nearby tissue radiate targeted cells and ultimately destroy cancer. This prevents unnecessarily exposing the whole body to radiation. (See Figures 1-9, below)
According to images offered by CT or MRI, and using computational optimization techniques, a three-dimensional conformal treatment plan is made for making the correct dose calculation that is necessary for killing cancer cells. Then, the number and location of seeds implanted is calculated. Seed implantation is often performed percutaneously (through the skin) under guidance of ultrasound or CT, as well as direct-visual guidance during operation. (See Figures 1-9, below)
HOW IS AN IMPLANT PERFORMED?
Before an implantation, an ultrasound volume study is done to see the size and location of the cancerous mass as well as the surrounding organs. During the pre-planning stage, a predetermination is made of how many seeds a patient will need and exactly where they should be placed; these details are based on the size and shape of the cancerous mass. At the beginning of the implantation, the patient will be given local anesthesia. To guide the precise placement of the seeds, an ultrasound probe is placed on the cancerous mass to obtain an image of the mass. Usually 20 to 100 seeds are placed inside needles that are inserted into the masses. The ultrasound probe ensures that the needles are guided with maximum accuracy based on the plan. (See Figures 1-9 below)
There is little discomfort after the implantation. This symptom usually goes away in a few days. Some men with prostate cancer may experience discomfort while urinating, or the need to urinate more frequently. These symptoms usually begin 1 to 2 weeks after implantation and gradually decrease over time as the seeds lose their strength. Drinking lots of fluids and avoiding caffeine and alcohol may help relieve these symptoms. A small percentage of men, particularly those who have had previous prostate surgery, may experience incontinence. Impotence may also occur in some men, particularly those over the age of 70. However, the rates of impotence and incontinence are lower with iodine-125 seeds than with other treatments. (See Figures 1-9 below)
SPECIAL PRECAUTIONS AFTER THE IMPLANTATION
Although seeds contain radioactive material, the patient is not radioactive. One of the benefits of seeds is that almost all radiation stays within the cancerous mass. After implantation, the patient can continue to enjoy physical contact with other adults. A physician may also recommend that patients avoid close contact with small children and pregnant women for the first 2 months after treatment.
Seed therapy is a local ablation; therefore, it is not harmful to whole body. It does not expose the entire body to radiation.
The seeds cannot be absorbed by body or excreted out of body. Thus, it is not harmful to the people near the patient or the surrounding environment.
There are none of the side effects that are associated with the traditional combination of chemo/radiotherapy.
Seed implantation can be performed percutaneously and is a minimally invasive procedure.
As a primary or supplementary modality, seed implantation can be used for: prostate cancer, tumors of soft tissue (sarcoma), brain cancer (glioma), breast cancer, pancreatic cancer, liver cancer, tongue cancer, oral cancer, pharyngeal cancer, nasopharyngeal cancer, cervical cancer, ovary cancer, thyroid cancer, and metastatic lymph nodes.
Ideal for eradication of unresectable or residue lesions during or after the operation, and for the prevention of cancer recurrence.
Brachytherapy complements cryosurgery. Often, both procedures will be performed together during one surgery session.
The following is an example of how brachytherapy would be performed on prostate cancer: