Prostate cancer brachytherapy

Brachytherapy is a type of radiotherapy.

There are two types of brachytherapy – high dose-rate (HDR) and low dose-rate (LDR).

LDR brachytherapy is the one most commonly used to treat prostate cancer. 

It may be referred to as ‘seed implantation.

Particles are known as seeds, and they can be inserted linked together as strands, or individually. 

The seeds deliver high doses of radiation to the tumour without affecting the normal healthy tissues around it. 

The procedure is less damaging than conventional radiation therapy, where the radioactive beam is delivered from outside the body and must pass through other tissues before reaching the tumor.

In addition to seeds, a polymer-encapsulated LDR source is available, which creates a very homogenous dose distribution.

Under a general anesthesia, the radioactive seeds are injected through fine needles directly into the prostate.

The seeds are permanently implanted.

The radioactivity decays naturally and safely over time.

Brachytherapy requires no incisions and is normally carried out as an outpatient procedure. 

Most men can return to work or normal daily activities within a few days. 

LDR brachytherapy has fewer side-effects with less risk of incontinence or impotence than other treatment options.

Isotopes used include iodine 125 (half-life 59.4 days) palladium 103 (half-life 17 days) and cesium-131 (half life 9.7 days).

The radiation does not affect the rectum, at all.

When prostate brachytherapy is carried out, an ultrasound probe is inserted into the rectum, and images from this probe are used to assess the size and shape of the prostate gland. 

 The seeds are inserted in the exact locations identified at the beginning of the procedure. 

Brachytherapy usually takes 1–2 hours.

Radioactive seeds are inserted into the prostate gland using needles which pass through the skin between the scrotum and the rectum.

Between 70 and 150 seeds are placed into the prostate, using a grid or template to pinpoint the exact positions in the prostate where the seeds are to be placed. 

A computer software program is used to make sure the prostate gland is completely covered by just the right dose of radiation to ensure that all cancer cells present in the prostate have been completely treated.

The seeds or sources slowly release their radiation. 

While contact with adults are fine, for the first two months following seed implantation, small children and pregnant women should not be in direct contact with the patient for prolonged periods.

Sexual intercourse can should be avoided for a few weeks. 

It is advisable to use a condom for the first two or three occasions of intercourse following LDR brachytherapy, as occasionally a seed can be expelled in the semen on ejaculation.

LDR prostate brachytherapy is recommended as a treatment for patients whose cancer is at an early stage (cancer stages T1 to T2), and which has not spread beyond the prostate.

LDR brachytherapy in combination with external beam radiotherapy may also be recommended for patients with later-stage cancer and higher PSA level and Gleason score.

The rate of survival with no increase in average PSA levels after LDR brachytherapy is similar to that achieved with external beam radiotherapy and radical prostatectomy.

However LDR brachytherapy has a lower risk of some of the complications associated with other treatment options.

Patients may experience urinary problems for the first six months and lasting problems are rare, only occurring in about 1–2% of patients.

Urinary problems may include:  urinary incontinence, stress incontinence or urge incontinence, difficulty with urination, and urinary retention. 

Long term, significant obstructive symptoms or persistent urinary retention requiring TURP occurred in 0–8.7% of patients. 

Urinary incontinence was found in up to 19% of patients treated by implant who had not had a previous TURP.

The percentage was a lot higher in those who did have prior TURP, up to 86%.

Stress incontinence from  prostate brachytherapy is a result of direct damage to the external urethral sphincter that results from the radiation. 

Stress incontinence treatment may include lifestyle changes, bladder training, and the use of incontinence pads. 

Surgical treatment in those who fail initial therapy can include the use of a urethral sling or an artificial urinary sphincter.

Less than 10% report an increase in bowel problems of diarrhea or urgency of the bowels, after prostate brachytherapy.

Radiation proctitis can be found in 0.5–21.4% of patients who received prostate brachytherapy due to the proximity of the prostate and the large bowel.

Fistula-occurring in 1–2.4% of patients.

Erectile dysfunction ranges from 25 to 50% of men who receive prostate brachytherapy, which is less than that observed in men receiving standard external beam radiation.

Mot many men will see significant improvement in potency, and occasionally the numbers may worsen.

Any bleeding disorder is a contraindication of brachytherapy for prostate cancer.

Aspirin or anticoagulants should stop prior to brachytherapy.

Combination with external beam radiation therapy is used for patients with intermediate or higher risk of failure with life expectancy greater than five years.

Prostate cancer brachytherapy exclusion criteria: Prostate volume bigger than 60 cm³, TURP within six months, tumor infiltration of bladder neck, significant urinary tract obstructive symptoms, pubic interference, lack of proper positioning.

Absolute prostate cancer brachytherapy contraindications include: rectal fistula, impossibility of anesthesia administration.

After treatment PSA, increase in resultant biopsy may not be interpretable within 30 months after implantation of radiation seeds.

Obesity and BMI are not contraindications to therapy.

PA 10 ngmL or less, Gleason score 6 or lower are appropriate pretreatment factors.

If Gleason super score is seven or greater, and PSA is greater than 10 ng/mL, a higher stage than 2B patients should have supplemental external beam radiotherapy.

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