IMPLANTS FOR THE TREATMENT OF PROSTATE CANCER

Prostate cancer is the most common type of cancer of the male reproductive and urinary tracts, occurring in a mild form in almost one half of American men over 60 years of age. If not treated early and effectively, however, prostate tumors can start to grow and spread into other tissues such as bone. Although only a small proportion of prostate cancers progress to this severe stage, the ones that do can spread relatively quickly and are not easily treated or cured.

Treatment options

To ensure that prostate cancer does not develop further and is halted soon after diagnosis, physicians recommend early treatment to either remove or kill the tumor. Until recently, there were only two basic forms of treatment, surgery and external radiation therapy aimed at the prostate gland.

In the early 1970s, a new approach was developed to confine radiation exposure to the prostate gland, increase radiation dosage to the tumor in order to kill the cancer, and minimize side effects. Researchers began to implant radioactive iodine (I-125 seeds) directly into the prostate, thereby providing internal radiation therapy exactly where it was needed. In these early attempts, surgery was performed to expose the prostate gland (which is known as open retropubic surgery) and the radioactive seeds were implanted by the surgeon essentially freehand, without the aid of imaging techniques now available. This early method of prostate implantation began at New York City's Memorial Sloan-Kettering Cancer Center. Although other radioactive agents are available, I-125 appears to be well suited for prostate implantation. It gives off very low energy radiation, or X-rays, that do not travel outside the prostate gland and pose no threat to patients or those in close contact with them. In fact, up to 90% of I-125 seed radiation is used up by six months, with all of it gone in 1 year.

Development of Improved Methods for I-125 Seed Implantation

After about 1000 implants the surgical method was abandoned at Memorial Sloan-Kettering because it produced success rates inferior to prostate removal or external radiotherapy techniques. The subsequent development of an implant allowed more precise placement of I-125 seeds without an operation or an incision. Since 1985 a method has been devised that allows very accurate placement of the I-125 seeds. Now the ultrasound machine plus fluoroscopy permits a very accurate placement and distribution of I-125 seeds.

Who Are the Best Candidates for Implantation of I-125 Seeds?

Patients with early-stage and small prostate tumors are the best candidates. That means that about 50% of the patients with prostate cancer will fit this criteria. The development of more sensitive tumor detection techniques means that prostate cancer patients are being diagnosed at earlier stages, permitting more of them to become potential candidates for I-125 seed implantation.

What should you expect?

Before you undergo the seed implantation procedure you need to have a prostate volume study. This is a procedure where the prostate gland is measured with the ultrasound machine and then reconstructed into a three dimensional diagram to plot the location and the number of seeds needed for the procedure. You will be asked to undergo the same preparation for the prostate volume study as you did for the prostate biopsy. That usually consists of an enema and no food or fluids the morning of the study.

Some patients will need to have their lymph nodes examined. This can be either done through an operation or through the laparoscope. The latter is in the insertion of a tube in the abdomen and removing the lymph nodes to determine if there is any spread of the cancer outside of the prostate gland.

The I-125 seed implantation is most often performed as an outpatient procedure and takes 1-2 hours to complete. You may have a catheter in the bladder for a day or two and you may experience some blood in the urine and burning on urination for a few days. Within 3-4 days, you can return to your active lifestyle-even playing golf and tennis.

The I-125 seed implantation technique is associated with apparently fewer and less severe side effects than surgery or external beam radiotherapy. Patients are less tired and have less diarrhea than they do after external beam therapy which usually requires 6-8 weeks of daily treatments. The I-125 technique is associated with a very low incidence of incontinence (urgency incontinence), which may occur in as many as 4-8% of patients undergoing prostate surgery. In addition, implantation patients have experienced only 20-25% decreases in sexual potency, which may occur in nearly 50% of those patients that have radical surgery or external radiotherapy.

The preliminary data shows that patients with early stage prostate cancer who receive implants enjoy as great a success rate as that of surgery or external radiation. These data must be construed as experimental at this point until long term follow-up is available. All patients will need to be followed by the urologists or radiation oncologists with periodic rectal examination and PSA (prostate specific antigen) testing. In addition to trying to achieve equivalent treatment success and fewer side effects, the I-125 seed implantation technique is approximately 35% less costly than either surgery or external beam radiation. The procedure minimizes length of hospital stay and expense in our already over-burdened health care system. In this era of cost-containment, the I-125 seed implantation technique may offer the most rapid and least expensive method of treatment with the least side effects.