Prostate Brachy

Indications for Brachytherapy

Clinical Exclusion Criteria:

  • Life expectancy , 5 years
  • Large or poorly healed TURP defect
  • Unacceptable operative risks
  • Distant metastases

Relative Contraindications for Brachytherapy:

These patients are not ideal candidates for brachytherapy, but have nevertheless been successfully implanted. Beginners should not implant these patients. Patients at increased risk of developing complications.

  • Large median lobes
  • Previous pelvic irradiation
  • High AUA score
  • History of multiple pelvic surgeries
  • Severe diabetes with healing problems

Technical difficulties which may result in inadequate dose coverage

  • Previous transurethral resection of prostate (TURP)
  • Gland size > 60 cc at time of implantation
  • Prominent median lobe
  • Positive seminal vesicles

Brachytherapy as Monotherapy:

  • Stage T1 to T2a and
  • Grade Gleason sum 2–6 and
  • PSA < 10 ng/ml

Brachytherapy as a Boost to EBRT:

  • Stage Clinical T2b, T2c or
  • Grade: Gleason sum 8–10 or
  • PSA . 20 ng/ml

Other possible indications for Brachytherapy as a Boost to EBRT:

  • Perineural invasion
  • Multiple positive biopsies
  • Bilateral positive biopsies
  • MRI positive for capsular penetration

Brachytherapy (including Boosting EBRT) in Conjunction with Androgen Deprivation:

  • Patients with initially large prostate (> 60 cc) that have downsized sufficiently

Treatment Technique

  • modified peripheral loading to reduce urethral complications with homogenous loading

Isotope and Dose

  • I-125 uses 144 Gy prescribed to the isodose surface that completely encompasses the prostate as contoured
    • half-life of I-125 is 60 days
    • mean photon energy of 27 KeV
    • initial dose rate of 7 cGy/hr
  • Pd-103 uses 125 Gy
    • half-life of Pd-103 is 17 days
    • mean photon energy of 21 KeV
    • initial dose rate of 19 cGy/hr
Procedure I-125 Pd-103
Boost Therapy 110 Gy 100 Gy
Monotherapy 145 Gy 125 Gy

Postimplantation Dosimetric Evaluation

  • A dose-volume histogram (DVH) of the prostate should be performed
  • D90 (dose to 90% of the prostate gland) ≥ 100%[1]
    • D90 should be < 130% of the prescription
  • V100 ≥ 90% of the prescription dose [1]
  • the rectal, and urethral doses should be reported
  • (CT)-based dosimetry should be done at 1 month following the implant.
  • Urethral dose
    • urethral D10: mimimum dose received by hottest 10% of CT-defined urethra volume
    • D10 < 150% Rx dose
  • Rectum (based on data from Mount Sinai)
    • R100 ≥ 1.3 cc resulted in 18% [2]
    • R100 < 1.3 cc had 5%.[2]
Bibliography
1. Wallner K, Merrick G, True L, Sutlief S, Cavanagh W, Butler W. 125I versus 103Pd for low-risk prostate cancer: preliminary PSA outcomes from a prospective randomized multicenter trial. Int J Radiat Oncol Biol Phys. 2003 Dec 1;57(5):1297-303.
2. Snyder KM, Stock RG, Hong SM, et al. Defining the risk of developing grade 2 proctitis following 125I prostate brachytherapy using a rectal dose-volume histogram analysis. Int J Radiat Oncol Biol Phys 2001;50:335–341.
Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-Share Alike 2.5 License.