title: Refining prostate seed brachytherapy: Comparing high-, intermediate-, and low-activity seeds for I-125 permanent seed prostate brachytherapy.
abstract: OBJECTIVE
  To analyze the difference in prostate coverage and dose to the rectum in men with prostate carcinoma treated with permanent seed brachytherapy with different seed activities.
  
  
  METHODS
  Forty-nine patients treated with iodine-125 permanent seed prostate brachytherapy with low-activity seeds of 0.30-0.37 mCi were identified. For each of these patients, 2 patients with similar prostate volume (±2 cc) were paired: one treated with intermediate seed activity (0.44-0.46 mCi) and one with high seed activity (0.60-0.66 mCi). The doses to prostate and rectum were compared using CT on Day 30.
  
  
  RESULTS
  A total of 147 patients divided into the three seed activity groups were analyzed. Mean prostate volume was 35.7 cc (standard deviation [SD], 11.70). Compared with low-activity seeds, implants with high-activity seeds consisted of an average of 22 seeds and 4.7 needles less. The dose to the prostate (prostate volume receiving 100% of the prescribed dose [V100], prostate volume receiving 150% of the prescribed dose, and minimal dose covering 90% of the prostate volume expressed in Gy) was not higher on Day 30 (p = 0.58-0.97). The mean volume (in cubic centimeters) of rectal wall receiving 100% of the prescribed dose (V100) increased with activity: low activity, 0.34 cc (SD, 0.49), intermediate activity, 0.47 cc (SD, 0.48), and high activity, 0.72 cc (SD, 0.79) (p = 0.009). There was a trend (p = 0.073) toward a higher frequency of clinically unfavorable rectal dosimetry (V100 > 1.3 cc) in patients with high-activity seeds (16.7%) compared with low-activity (6.3%) or intermediate-activity (4.2%) seeds.
  
  
  CONCLUSIONS
  High-activity seeds do not result in a higher dose to the prostate but in a higher dose to the rectum.
authors: Department of Radiation Oncology, Centre hospitalier de l'Universiténde Montréal (CHUM), Hôpital Notre-Dame, Montreal, Canada; CRCHUM-Centre de recherche du Centre Hospitalier de l'Universiténde Montréal, Quebec, Canada.
authors: Guila
authors: G
authors: Delouya
authors: Department of Radiation Oncology, Centre hospitalier de l'Universiténde Montréal (CHUM), Hôpital Notre-Dame, Montreal, Canada.
authors: Pascal
authors: P
authors: Bahary
authors: Department of Radiation Oncology, Centre hospitalier de l'Universiténde Montréal (CHUM), Hôpital Notre-Dame, Montreal, Canada.
authors: Jean-François
authors: JF
authors: Carrier
authors: Department of Radiation Oncology, Centre hospitalier de l'Universiténde Montréal (CHUM), Hôpital Notre-Dame, Montreal, Canada.
authors: Renée-Xavière
authors: RX
authors: Larouche
authors: Department of Radiation Oncology, Centre hospitalier de l'Universiténde Montréal (CHUM), Hôpital Notre-Dame, Montreal, Canada.
authors: Yannick
authors: Y
authors: Hervieux
authors: Department of Radiation Oncology, Centre hospitalier de l'Universiténde Montréal (CHUM), Hôpital Notre-Dame, Montreal, Canada.
authors: Dominic
authors: D
authors: Béliveau-Nadeau
authors: Department of Radiation Oncology, Centre hospitalier de l'Universiténde Montréal (CHUM), Hôpital Notre-Dame, Montreal, Canada.
authors: David
authors: D
authors: Donath
authors: Department of Radiation Oncology, Centre hospitalier de l'Universiténde Montréal (CHUM), Hôpital Notre-Dame, Montreal, Canada; CRCHUM-Centre de recherche du Centre Hospitalier de l'Universiténde Montréal, Quebec, Canada. Electronic address: daniel.taussky.chum@ssss.gouv.qc.ca.
authors: Daniel
authors: D
authors: Taussky
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000473:pathology / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011874:Radiometry; D011879:Radiotherapy Dosage; D012007:Rectum / Q000528:radiation effects
chemical_list: D007457:Iodine Radioisotopes
keywords: Permanent seed brachytherapy; Prostate cancer; Source activity