title: Sector analysis provides additional spatial information on the permanent prostate brachytherapy learning curve.
abstract: OBJECTIVE
  To evaluate the permanent prostate brachytherapy (PPB) learning curve using postimplant multisector dosimetric analysis and to assess the correlation between sector -specific dosimetry and patient-reported outcome measures (PROMs).
  
  
  METHODS
  First 200 patients treated with (125)I PPB monotherapy (145 Gy) at a single institution were assessed. Postimplant dosimetry (PID) using CT was evaluated for whole prostate (global) and 12 sectors, assessing minimum dose to 90% of prostate (D90) and dose to 0.1 cm(3) of rectum (D0.1cc). Global and sector PID results were evaluated to investigate changes in D90 with case number. Urinary and bowel PROMs were assessed using the International Prostate Symptom Score and the Expanded Prostate Cancer Index Composite questionnaire. The correlation between global and individual sector PID and urinary/bowel PROMs was also evaluated.
  
  
  RESULTS
  Linear regression confirmed a significant improvement in global D90 with case number (r(2) = 0.20; p = 0.001) at a rate of 0.11 Gy/case. Postimplant D90 of base sectors increased at a rate of 0.11-0.15 Gy/case (p = 0.0001) and matched global improvement. The regression lines of midgland and apex sectors were significantly different from global D90 (p = 0.01). Posterior midgland sectors showed a significant reduction in D90 with case number at a rate of 0.13-0.19 Gy/case (p = 0.01). Dose to posterior midgland sectors correlated with rectal D0.1cc dose but not bowel PROMs. Dose to posterior midgland sectors correlated with urinary International Prostate Symptom Score change, which was not apparent when global D90 alone was considered.
  
  
  CONCLUSIONS
  Sector analysis provided increased spatial information regarding the PPB learning curve. Furthermore, sector analysis correlated with urinary PROMs and rectal dose.
authors.affiliation: Department of Radiotherapy Medical Physics, Northern Ireland Cancer Centre, Belfast City Hospital, Belfast, Antrim, Northern Ireland, UK. Electronic address: ahamed.badusha@belfasttrust.hscni.net.
authors.forename: Ahamed Badusha
authors.initials: AB
authors.lastname: Mohamed Yoosuf
authors.affiliation: Department of Clinical Oncology, Northern Ireland Cancer Centre, Belfast City Hospital, Belfast, Antrim, Northern Ireland, UK.
authors.forename: Darren M
authors.initials: DM
authors.lastname: Mitchell
authors.affiliation: Department of Radiotherapy Medical Physics, Northern Ireland Cancer Centre, Belfast City Hospital, Belfast, Antrim, Northern Ireland, UK.
authors.forename: Geraldine
authors.initials: G
authors.lastname: Workman
authors.affiliation: Department of Clinical Oncology, Northern Ireland Cancer Centre, Belfast City Hospital, Belfast, Antrim, Northern Ireland, UK.
authors.forename: Sai
authors.initials: S
authors.lastname: Jonnada
authors.affiliation: Department of Radiology, Northern Ireland Cancer Centre, Belfast City Hospital, Belfast, Antrim, Northern Ireland, UK.
authors.forename: Eoin
authors.initials: E
authors.lastname: Napier
authors.affiliation: Department of Clinical Oncology, Northern Ireland Cancer Centre, Belfast City Hospital, Belfast, Antrim, Northern Ireland, UK.
authors.forename: Suneil
authors.initials: S
authors.lastname: Jain
mesh_terms: D000328:Adult; D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D059032:Learning Curve; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000150:complications / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D053448:Prostatism / Q000209:etiology; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D012007:Rectum / Q000528:radiation effects; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed
chemical_list: D007457:Iodine Radioisotopes
keywords: Global and sector analysis; Learning curve; Permanent prostate brachytherapy; Spatial dose distribution