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Brachytherapy for prostate cancer


Medical editor Oslo University Hospital

General

In brachytherapy, the radioactive source is implanted directly into the prostate. This involves a number of advantages compared to external radiation treatment.

Benefits compared to external radiation treatment

  • Problem with positioning of patient and organ movement is eliminated.
  • Allows increased dosing to the target volume and thereby possible increase in curative potential. 
  • Shorter treatment time
  • Saves normal tissue structures (especially rectum and bladder)

Disadvantages of brachytherapy

  • Invasive procedure with the need for anesthesia
  • Over dosing of urethra (the apex-region)
  • Obesity can cause technical problems
  • Increase in risk for complications in diabetes and symptom-causing arteriosclerosis in the pelvis
  • Risk of underdosage outside the prostate gland

To ensure the irradiation of possible microscopic cancer outside the prostate capsule, brachytherapy is always given combined with conformal (organ configured) external radiation therapy.
We destinguish between high-dose (HDR) and low-dose (LDR) brachytherapy.  In HDR, a boost dose is given with iridium 192 before external radiation therapy. The radiation sources are implanted transperineally. In LDR, the seeds are implanted with iridium 131 permanently in the prostate. Theoretically, there is a great difference between these two methods for administration of brachytherapy.  The practical implication of this is uncertain.

It can be appropriate to give hormone treatment in addition to the radiation therapy in patients where:

  • The volume of the prostate is large (< 60 cc)
  • The tumor has grown through the capsule (T3 and/or serum-PSA > 20 ng/ml and/pr Gleason score ≥ 8

Indications

  • T1/T2 pN0, PSA  ≥ 20
  • T1/T2 pN0, Gleason score ≥ 8
  • T2 pN0, 20 < PSA < 70
  • T3 pN0, PSA < 70

Contraindications

  • Obstructive symptoms from the urinary tract
  • IPSS > 12 (significant urine retention)
  • Pathology in urethra (tumor breakthrough, stenosis/strictures)
  • Infiltration to tthe rectum and/or seminal vesicles
  • TUR-P < 6 months or large cavity
  • Large adenoma  in the prostate (lobus tertius)
  • Large volume > 60 cc (many needles, os pubis)
  • A lot of prostate calcification
  • Serum PSA > 50
  • Previous rectal amputation

Goal

  • Curative treatment

 


Preparation

In addition to biopsy, measurement of PSA and possibly lymph node staging, the following is normally done:

  • Skeletal scintigraphy: To map possible metastases to the bone, a bone scan  is performed ahead of  radiation therapy. If the bone scan shows an increase in radioactive uptake, it may be necessary with supplementary x-ray examination, most often of the spine, pelvis, and hips.
  • Pulmonary x-ray

In some instances, MRI investigations and supplementary biopsies may also be necessary.

Neoadjuvant androgen block

For large prostates (>60 cc), hormone treatment before radiation therapy may be  appropriate. The prostate can shrink 40-50% after 3-6 months with LH-RH agonist treatment. Cytoreduction of target volume causes less toxicity and better oportunity for dose escalation.

At Oslo University Hospital, 6 month neoadjuvant therapy is given for:

  • T1/T2 with Gleason ≥ 8
  • T2 with PSA > 20
  • T3

Preparation of patient for HDR-brachytherapy

  • Fast previous night
  • Foley catheter is inserted in the morning of the treatment
  • Pre-medication one hour before scheduled treatment
  • Patients who are taking  long-term pain medication should take it as usual. An additional dose can be given with the rest of the premedication.
  • Enema is only given to patients with constipation to avoid unnecessary bowel  irritation after external radiating of the pelvis.

Implementation

HDR-Brachytherapy

Brachytherapy is performed under general or spinal anesthesia.

Brachytherapy is given as 10 Gy x 2 with two week intervals. Thereafter, conformal external radiation therapy 50 Gy over five weeks 1-2 weeks after brachytherapy. 

  • Patient in supine position with leg supports.
  • The ultrasound probe is placed in the rectum and contrast is introduced.
  • Based on the US examination, a preliminary assessment of the number of needles and their position in the prostate is done.
  • Multiple needles are introduced  parallel to each other transperineally into the prostate.
  • An ultrasound investigation is repeated to calculate radiation dose for each individual needle.
  • The radiation plan is assessed by an oncologist, who makes adjustments with regards to tumor and organs at risk such as bladder and rectum, and finally decides if one obtains an adequate irradiation.
  • The plan is then transferred to the treatment machine. This has in the mean time been connected to the inserted applicators.
  • Treatment is given (5-10 minutes). Pole-formed iridium 192 sources are fed into the applicators with after-loading technique. 
  • The equipment is removed and the patient can return to the bed.
  • Total time for the entire process is  on average 1 hour and 30 minutes.

Follow-up

Acute complications

  • Postoperative fever
  • Urethra/bladder
    • Cystitis symptoms
    • Pollakisuria
    • Incontinence
    • Hematuria
    • Dysuria can be treated with alfa-blocker and anti-inflammatory drugs
  • Rectum:
    • Tenesmus
    • Local soreness
    • Sphincter disturbances

Chronic complications

Related to total dose, radiated volume, fractioning, and patient related factors (diabetes, inflammatory bowel disease, previous pelvic operation)

  • Impotence
    • Up to 50% (30-60%), depending on age
    • It is important to resume sex life early after external radiation therapy before fibrosis worsens the condition
  • Chronic cystitis (4-8%), possibly with hematuria and bladder shrinkage
  • Urethra strictures (3-6%, increased risk by indwelling catheter
  • Chronic proctitis (1-4%)
  • Incontinence (0.5%-1.5%)
  • Osteoradionecrosis

Follow-up

Follow-up after 3, 6, 12, 18, 24, and 26 months. Thereafter, yearly for 5 years.

Additionally the patient should be seen by the referring physician at local hospital when appropriate.


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