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What is brachytherapy/interstitialseed 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

Actual size of 1-125 seeds used for brachytherapy.

Figure 13. Actual size of 1-125 seeds used for brachytherapy.

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 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[1], 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[2] 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[3] 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[4] involves placing a catheter through the penis into the bladder to drain the bladder on a regular schedule (usually every 4to6 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.

  • [1] A term used to describe the need to urinate 8 or more times per day.
  • [2] The inability to pass urine from the bladder.
  • [3] The passage of a catheter into the bladder to empty the bladder of urine.
  • [4] 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.
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