High Dose Rate Brachytherapy for prostate cancer is a newer technology which combines the advantages of intensity modulated external beam radiation and permanent seed implantation. We use the rationale, protocol and procedure and non-fixed template technique known as the California Endocurietherapy or CET method.1 There are essentially four steps as described below.
CET HDR method
A temporary matrix of thin hollow closed ended treatment catheters (called flexiguides) are implanted into the prostate through the perineal skin in the operating room under ultrasound and intra operative x ray guidance.2
Figure 1. Side view diagram of pelvis with temporary treatment catheters and template in place.
Typically about seventeen treatment catheters are implanted in the prostate. The catheters are placed at the prostatic capsule perimeter and within the substance of the gland which provides the matrix for an unlimited number of treatment points within the gland. In a typical prostate treatment plan there are between ten to fifteen points per flexiguide catheter which gives over two hundred treatment points within the prostate.
Then a series of computerized tomography cuts of the implanted matrix of treatment catheters is done which can be reconstructed to a virtual image of the prostate, prostatic urethra, seminal vesicles, bladder and rectum.3
Figure 2. CT cross section through the middle of the prostate gland showing the symmetric distribution of treatment catheters around the urethra in the center of the prostate and away from the rectum in the lower portion of the image.
Then computerized dosimetry calculations are done based on those images to optimize the dose to the prostate gland and keep the dose to the normal urethra, bladder and rectum below the normal tissue tolerance threshold.4
Figure 3. CT cross section of the prostate with the overlying dose curves. The dark red line is the prostate capsule. Note that treatment covers 5mm of normal margin around the gland and minimal dose to the urethra and rectum.
Figure 4. Three dimensional reconstruction of the dose curves showing prostate in purple, and the treatment catheters and treatment points in blue with patient on his back. The bladder is yellow, the urethra is green and the rectum is pink.
Then treatment is given under controlled conditions with a computerized robot that runs a single “seed” on the end of a cable into each one of the hollow treatment catheters in sequence.1,2
Figure 5. Patient in position for treatment and connected via transfer tubes to the computerized robot on the lower right.
Typically for low risk prostate cancer the patient stays overnight in the hospital and a second treatment is given the next morning and four to six hours later the third treatment is given. Then all the catheters are removed and the patient is discharged home. One week later the entire process is repeated so there are two overnight stays in the hospital separated by one week and a total of six treatments.
That sequence of high dose rate brachytherapy to the prostate gives the same cure rate stage for stage as radical surgery, external beam radiation or permanent seeds.
Patients who are in the high risk groups may have a combination of high dose rate brachytherapy and external beam radiation. In that case we recommend that the external beam radiation start approximately two weeks following HDR. In some cases this is combined with a course of androgen deprivation therapy as well.
Post Treatment Follow Up Care
After discharge home we encourage returning to normal activity. The only precaution is to not sit for prolonged periods. There will be some transient urinary and maybe bowel symptoms. We recommend a follow up visit about one week following the implant procedure because the temporary urinary and bowel symptoms are just passing their peak. Although we prescribe pain medication to take as needed at home, the majority of men find no need to take it. We then recommend follow up visits every three months for the first two years, then every six months to five years, then annually after that. The follow up includes a PSA blood test and digital rectal exam of the prostate. No special scans or studies are needed routinely. PSA testing requires correct interpretation because transient rises called PSA bounce occur in a few cases and should not be misinterpreted as treatment failures.28