(Radioactive Seed Implementation)
Brachytherapy is a form of radiation treatment in which tiny pellets containing radioactive material, such as Iodine-125 or Palladium-103, are implanted directly into the tumor-containing organ. This form of radiation therapy has long been used in other types of malignancies including cervical, breast, endometrial as well as head and neck cancers. Brachytherapy offers the appealing concept of delivering high doses of radiation to the prostate while limiting the radiation dose to the adjacent organs.
Brachytherapy of the prostate dates back to 1911, when Pasteau published the first case in medical literature. Utilizing a technique rather crude by today’s standards, Pasteau used a catheter to insert radium into the prostate urethra. Although the results showed fairly good local control of the cancer, the complications were too high to be considered acceptable.
Dr. Flocks, a urologist in Iowa, developed a technique using colloid gold, injecting it into the prostate for treatment. With the advent of high-energy linear accelerators, the interest in prostate brachytherapy waned.
Dr. Whitmore introduced an open brachytherapy method in 1972, using Iodine-125 or gold-198. Because the seeds were not always placed uniformly, the clinical results were less than satisfactory and the complication rates related to the surgical procedure were too high and unacceptable.
These early failures, to a large degree, were due to the fact that they were performed utilizing “blind” approaches. Imaging technologies, such as transrectal ultrasound, crucial for seed implantation, were not yet available. Some researchers tried temporary implantation with iridium-192 using an open surgical field, but they were still unable to visualize the internal structures of the gland. This technique was also burdened by the limitations of a blind approach. Precise placement of seeds is a crucial factor in the success of brachytherapy. Without the benefit of modern day imaging techniques, accurate placement of the radioactive seeds was not attainable.
In the early 1980s, the old concept of brachytherapy was revisited. Improved imaging technologies made the procedure more feasible. The most important of these were transrectal ultrasound (TRUS) and computerized tomography (CT). These new technologies allowed a non-surgical, uniform seed distribution into the prostate through needle punctures. With recent developments in computer software, TRUS has become the most commonly used modality for seed implantation procedures. However, the results can be highly operator-dependent.
Candidates for Bracytherapy (Seed Implant)
In determining who is a candidate for seed-implant therapy, there are several factors that must be considered. The patient’s general state of health is a very important factor in determining which form of therapy should be chosen. Since this procedure is only minimally invasive, it is better tolerated than the more aggressive surgical procedures. The age of the patient is also important for this same reason. Therefore, an older patient that requires treatment may consider brachytherapy as an option.
Accurate staging of the tumor is mandatory before considering brachytherapy. A good color Doppler Ultrasound examination with staging biopsy is key to the accurate staging. Patients with early-stage, small volume tumors are the best candidates for this procedure. Treatment with implants alone (either iodine-125 or palladium-103) is usually adequate for early stage small volume prostate cancer. For larger volume tumors, brachytherapy is usually performed in combination with additional external-beam radiation.
Younger patients with early small volume tumors may also choose brachytherapy because of the lower complication rates. This is especially true when impotency is a major consideration. Nevertheless, concerns over impotency should not allow the tumor treatment to be compromised. There are newer drug therapies that will allow impotent men to regain erections.
The treatment decision is a highly personal one that involves both medical, personal and life-style issues. The most important first step is that the patient needs to have his tumor accurately staged. Under staging (underestimating) a cancer is the most common reason for patients choosing inappropriate treatment options. This often leads to subsequent treatment failures.
Procedures Prior to Seed Implant
A precise prostate volume study, utilizing a dedicated transrectal ultrasound machine, is performed to create a road map for seed implantation. This is usually done 2-3 weeks before treatment. This study is transferred to a computer treatment program that determines the optimal number of seeds, needles and the distribution in the prostate in order to achieve the proper dose.
Routine pre-operative tests (Blood test, EKG, chest X-ray etc.) will be done a few days before the treatment. Specific instructions will be given to you regarding diet and bowel prep.
Procedures During Seed Implant
Unless there are contraindications (preventing factors), the procedure is performed in the operating room under spinal or general anesthesia.
An ultrasound probe is inserted into the rectum to image the prostate. The prostate is continuously visualized during the course of the procedure.
Based on the planning map, an average of 60-120 seeds are placed in the prostate through a needle that is placed through the perineum (skin between the rectum and the scrotum). The ultrasound guidance provides for precise and accurate positioning of the seeds.
Intra-operative real time dosimetry programs identify a radiation field on the computer screen any time a seed is placed in the prostate during the procedure. If a cold spot (poor radiation field) is detected, an extra seed is placed to correct the radiation distribution. Therefore, near perfect implantation is achieved.
At the end of the procedure, a catheter is temporarily inserted into the patient’s bladder to assure adequate drainage of urine. The entire seed placement procedure takes about one hour.
Procedures After Implant
The patient is transferred to a recovery room and remains there approximately two hours with an ice bag placed at the needle entry site in the perineum. This is done to reduce local swelling. The Foley catheter is removed after the anesthesia has worn off and the patient has regained urinary control. Occasionally, the catheter may be left in overnight.
The patient is usually discharged that same day. However, it is strongly recommended that he not drive himself home. There are no diet restrictions. Heavy lifting and/or strenuous exercise are prohibited for approximately two weeks.
Potential dangers of radiation to the family members are almost non-existent. Iodine-125 emits very low energy radiation, which is mostly contained in the region of the prostate. However, small amounts of radiation may escape from the prostate and travel a short distance. It is also possible for very small amounts of radiation to escape the body when a patient passes a radioactive pellet through the urine. For this reason, it might be prudent to avoid contact small children or pregnant women during the first two months following implantation.
Clinical Outcome and Complications
Recent 12 year follow-up data (Ragde, Cancer, July 2000) shows a 66% biochemical disease free rate (PSA < 0.5 ng/ml). Dr. Bahn’s data, containing more advanced cancer patients than Ragde’s study, also showed 67.5% biochemical disease free rate. When the PSA < 1.0 ng/ml is used as a criterion for disease free status, it was 86%. The results are very similar to cryotherapy statistics. However, it should be noted that the patient selection process was more stringent in seed implant group. Seed implantation therapy is only offered to a select group of patients who have small-volume, early-stage cancer.
Complication rates are generally lower in brachytherapy than with other modalities. Complications include proctitis, cystitis, incontinence and rectal bleeding. Current literature reports that significant rectal complications can occur in 5-10% of patients and urethral complications can occur in 10-14%.
It is common to experience problems with urination for a few months after seed implantation. Various degrees of impotency are also common after the procedure. The reported impotency rates are in the 20-30% range. However, there is also a correlation to the patient’s age and general state of health.
As with cryotherapy, the brachytherapy procedure is highly operator-dependent. If a patient is considering brachytherapy, he should look for the following:
- An institution that utilizes the highest quality color-Doppler ultrasound equipment.
- Intra-operative real time dosimetry capability.
- Physician experience of a minimum of 100 patients.