title: Impact of learning curve and technical changes on dosimetry in low-dose brachytherapy for prostate cancer.
abstract: OBJECTIVE
  To assess the impact of experience and technical changes on peri- and postimplantation (1 month later) dosimetry for permanent prostate brachytherapy (PPB).
  
  
  METHODS
  From July 2003 to May 2010, 150 prostate cancer patients underwent low-dose, loose-seed I(125) PPB as monotherapy with intraoperative planning. Patients were divided into three groups-P1 (n = 64), P2 (n = 45), P3 (n = 41)-according to the technical changes that occurred during the study period: use of an automatic stepper at the beginning of P2 and a high-frequency ultrasound probe in P3. Peri- and postimplantation dosimetric parameters (on day 30) were reported: D90 (dose received by 90% of prostate volume), V100 and V150 (prostate volume receiving, respectively, 100% and 150% of the prescribed dose), D2 cc and D0.1 cc (doses received by 2 cc and 0.1 cc of the rectum), R100 (rectum volume that received 100% of the prescribed dose), and D10 and D30 (doses received by 10% and 30% of the urethra, only during peri-implantation).
  
  
  RESULTS
  We observed a decrease in the number of needles and seeds used over time. The mean peri-implantation D90 was 187.52 Gy without a significant difference between the three periods (p = 0.48). The postimplantation D90, V100, and V150 parameters were, respectively, 168.3 Gy, 91.9%, and 55% with no significant difference between the three periods. The peri-implantation and postimplantation D0.1 cc and R100 significantly decreased over time; on day 30: D0.1 cc P1 = 223.1 Gy vs. D0.1 cc P3 = 190.4 Gy (p = 8.10(-5)) and R100 P1 = 1.06 cc vs. R100 P3 = 0.53 cc (p = 0.0008).
  
  
  CONCLUSIONS
  We observed a learning curve for the implantation parameters, which led to a significant decrease in the rectal doses without having any impact on the prostate dosimetric parameters.
authors.affiliation: Radiation Therapy Department, CHU Brest, 5 avenue Foch, 29200 Brest, France. emmanuelle.lefur@chu-brest.fr
authors.forename: E
authors.initials: E
authors.lastname: Le Fur
authors.forename: J P
authors.initials: JP
authors.lastname: Malhaire
authors.forename: D
authors.initials: D
authors.lastname: Baverez
authors.forename: F
authors.initials: F
authors.lastname: Delage
authors.forename: M A
authors.initials: MA
authors.lastname: Perrouin-Verbe
authors.forename: F
authors.initials: F
authors.lastname: Schlurmann
authors.forename: S
authors.initials: S
authors.lastname: Guerif
authors.forename: G
authors.initials: G
authors.lastname: Fournier
authors.forename: O
authors.initials: O
authors.lastname: Pradier
authors.forename: A
authors.initials: A
authors.lastname: Valeri
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000295:instrumentation*; D004502:Education, Medical, Continuing; D006801:Humans; D007318:Inservice Training; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D059032:Learning Curve; D008297:Male; D008611:Mentors; D008875:Middle Aged; D009367:Neoplasm Staging; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D018787:Radiation Oncology / Q000193:education; D011874:Radiometry / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation*; D014572:Urology / Q000193:education
chemical_list: D007457:Iodine Radioisotopes