What is brachytherapyinterstitialseed therapy Who is a candidate What are the risks

Brachytherapy derives from the Greek word brachy, which means near to. Brachytherapy is a technique in which either permanent radioactive seeds (Figure 13) or

Greek Word Prostate

temporary needles are placed directly into the prostate gland. Palladium 103 and iodine 125 are two radioactive agents that can be used for permanent seed placement and both are effective in the treatment of prostate cancer. Palladium gives a higher initial dose of radiation when it is placed, and some people think that it may be more helpful in high-grade, fast-growing tumors. Palladium tends to be used for tumors with a Gleason score of at least 7, and iodine is used for tumors with a Gleason score of 6 or lower. Before the seeds are placed, either a transrectal ultrasound or a CT scan of the prostate is performed to assess the prostate volume. This helps determine needle placement and seed positioning within the needle. Typically, the target volume includes the original prostate volume plus 2-mm margins laterally and anterior to the prostate gland, as well as additional 5-mm margins at the top and bottom of the prostate. This measurement is done to try to ensure that the pro-static capsule is included in the treatment. No additional margins are added posteriorly to prevent injury to the rectum. It is also important to limit the dose received by the urethra to prevent urethral irritation. Typically, a dose of 144 Gy is given for iodine 125, and 125 Gy is given for palladium 103. Iodine 125 has a half-life of 60 days, whereas palladium has a half-life of only 17 days.

The most commonly encountered side effects of interstitial seed therapy include voiding troubles related to

Frequency

A term used to describe the need to urinate 8 or more times per day.

Acute urinary retention

The inability to pass urine from the bladder.

Catheterization

The passage of a catheter into the bladder to empty the bladder of urine.

Clean intermittent catheterization

The placement of a catheter into the bladder to drain urine and the removal after the urine is drained at defined intervals throughout the day, to allow for bladder emptying. It may also be performed to maintain patency after treatment of a bladder neck contracture or urethral stricture.

bladder outlet obstruction, urinary incontinence, and rectal ulceration and bleeding. In addition, in some patients a benign increase in the PSA may occur after interstitial seed therapy. Urinary symptoms occur earlier with palladium because it releases high energy earlier than iodine. Individuals may develop urinary frequency, dysuria, or urinary retention. Urinary symptoms, if they are not associated with urinary retention, are often treated with nonsteroidal anti-inflammatories and an alpha-blocker, such as doxazosin (Cardura), terazosin (Hytrin), alfu-zosin (Uroxatral), tamsulosin (Flomax) and silodosin (Rapaflo). They often resolve over 1 to 4 months, but may persist for 12 to 18 months.

Bladder Outlet Obstruction

Trouble urinating after interstitial seed therapy occurs in 7 to 25% of patients, possibly as a result of blood clots in the bladder or swelling of the prostate. About 10% of men will experience acute urinary retention requiring temporary placement of a Foley catheter. Your doctor may want you to try some medications, including an alpha-blocker, such as doxasin (Cardura), terazosin (Hytrin), tamsulosin (Flomax) or silodosin (Rapaflo), and/or an anti-inflammatory (e.g., ibuprofen) (see Question 39). If you are not able to void for awhile, then a suprapubic tube or clean intermittent catheterization may be easier for you. A suprapubic tube is a catheter that is placed through the skin of the lower abdomen into the bladder to drain the urine. It remains in place until you can urinate on your own. It has the advantages of being able to be changed on a monthly basis in your urologist's office, and it does not cause urethral irritation like a Foley catheter.

Clean intermittent catheterization involves placing a catheter through the penis into the bladder to drain the bladder on a regular schedule (usually every 4 to 6 hours) throughout the day. The advantages of clean intermittent catheterization are that it allows you to know when you are able to void on your own, it minimizes bladder and urethral irritation, and it has less risk of infections and bladder stones over the long term. Although it is discouraging to be unable to urinate after the procedure, it is important to allow time to pass and see whether the problem will resolve. A TURP should be delayed to give you a sufficient trial because of the increased risk of urinary incontinence.

Urinary Incontinence

Urinary incontinence is uncommon in men undergoing interstitial seed therapy affecting < 1%. However, in men who have had a prior TURP, the risk of incontinence is 25% and is up to 40% if more than one TURP has been performed.

Rectal Ulceration/Bleeding

Rectal irritation does not occur as commonly as urinary symptoms and tends to improve quicker than urinary symptoms do. Fewer than 5% of patients will have a rectal ulcer or rectal bleeding, which occurs as a result of irritation of the rectal lining. It may be associated with pain, rectal spasms, and the feeling that one needs to have a bowel movement. This condition can be treated with several topical medications, including Anusol, hydrocortisone, Proctofoam hydrocortisone, mesalamine (Rowasa) suppositories, Metamucil, and a low-roughage diet.

Clean intermittent catheterization involves placing a catheter through the penis into the bladder to drain the bladder on a regular schedule (usually every 4 to 6 hours) throughout the day.

PSA "Bounce" or "Blip"

This occurs when the PSA increases on two consecutive blood draws and then decreases and remains low without rising again. The cause of this phenomenon is not known. It occurs in about one-third of men treated with interstitial seeds and typically occurs around 9 to 24 months after the treatment. It may or may not be accompanied by symptoms of prostate inflammation; if such symptoms are present, then treatment for prostati-tis may decrease the symptoms and the PSA level.

Urethral Stricture

This narrowing of the urethra is related to the development of scar tissue and occurs in 5 to 12% of men, and tends to develop later. It may present with a change in the force of stream or the need to strain to void. A stricture is identified by cystoscopy in the doctor's office. Treatment of the stricture depends on the location and the extent of the stricture; it may require simple office dilation or an incision under anesthesia.

Erectile Dysfunction

This condition may occur in as many as 40 to 60% of men who undergo interstitial seed therapy. Unlike radical prostatectomy, the erectile dysfunction tends to occur a year or more after the procedure and not right away. As with post radical prostatectomy ED, there are a variety of options available to treat it (see Part Three, Erectile Dysfunction).

Who is a candidate for interstitial seed therapy ? Similar to radical prostatectomy, the goal of interstitial therapy is to cure the patient of prostate cancer. With this in mind, the candidate should have a life expectancy of more than 7 to 10 years and no underlying illness that would contraindicate the procedure such that he will not benefit from a cure. Men with significant obstructive voiding symptoms and/or prostate volumes greater than 60 mL are at increased risk for voiding troubles and urinary retention after the procedure. Men who have undergone a prior TURP are at increased risk for urinary incontinence after brachytherapy. Men with clinically localized prostate cancer of low to intermediate risk are candidates for interstitial seed therapy. Men with high-risk prostate cancer (PSA > 20 ng/mL, Glea-son score > 8, or stage T3a prostate cancer) should not be treated with interstitial seed therapy alone. Depending on your risk, hormonal therapy may be used in addition to interstitial seed therapy.

In some individuals who are deemed to be at higher risk, external beam radiation therapy may be used in addition to interstitial seed therapy. Interstitial seed therapy is limited in its ability to reach tissue outside of the prostate, especially the back of the prostate. The addition of EBRT may help in patients who are judged to be at high risk for disease penetrating through or outside the prostate capsule. Use of interstitial seeds alone is appropriate for patients with tumors in clinical stage T1c to T2a, a Gleason score < 6, and a PSA < 10. Patients with a Gleason score of 7 or greater, a PSA > 10, tumors in clinical stage T2b or minimal T3a, and at least four of six biopsies positive for cancer or per-ineural invasion on the biopsy appear to be the best served by the combination of interstitial seeds and EBRT.

Men with

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i-h

prostate cancer oflow to intermediate

c r

risk are

candidates for

interstitial

seed therapy.

How is one monitored after interstitial seed therapy and what is the success rate?

Unlike with radical prostatectomy, the prostate remains in your body, and thus the PSA does not decrease to an undetectable level. In addition, it may take at least 2 years for the PSA to reach its lowest level (PSA nadir). The PSA is typically checked 1 month after seed

PSA nadir

The lowest value that the PSA reaches during a particular treatment.

placement, then every 3 to 6 months for 2 years thereafter if the level remains stable. After 2 years, the PSA is checked yearly. In January 2005 the definition of PSA failure after radiation therapy was refined. The Phoenix definition defines PSA failure after radiation therapy as a rise by 2 ng/ml or more above the nadir PSA with or without the use of androgen blockade.

A rise in PSA may occur in as many as one third of the patients between the first and second year after the implantation. This is called a benign PSA bump, and it appears to be related to late tissue reactions to the radiation, but it does not mean that the seeds have failed or that you are at increased risk of failure. In this situation, the PSA does not continue to rise, and this is how one differentiates a PSA bump from a failure.

The results of prostate brachytherapy are comparable to those of radical prostatectomy for 5 to 7 years after treatment. The long-term data (i.e., the data for longer than 10 years after treatment) are limited. Reported studies demonstrate success rates of 64 to 85% at ten years, with success being defined by either a PSA < 0.5 ng/mL or the absence of three consecutive rises in PSA in patients who received brachytherapy EBRT.

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