title: Assessment of testicular dose during preoperative radiotherapy for rectal cancer.
abstract: BACKGROUND
  Radiotherapy (RT) for rectal cancer can have adverse effects on testicular function resulting in azoospermia and low testosterone levels. Variability of testicular dose (TD) due to differences in position of testes has been assessed with scrotal dosimeters and resulted in substantial variability of delivered TD. The aim of this study was to estimate planned and delivered TD using a treatment planning system (TPS).
  
  
  METHODS
  In 101 men treated with RT for rectal cancer the cumulative mean TD (mTD) was calculated by TPS based on plan-computed tomography (CT) to evaluate the effect of different predictors on planned TD. The delivered TD was estimated by TPS based on repeated cone-beam CTs in 32 of 101 men to assess within-person variability of planned and delivered TD in a longitudinal analysis.
  
  
  RESULTS
  The median planned mTD for short course RT was 0.57 Gy (range 0.06-14.37 Gy) and 0.81 Gy (range 0.36-10.80 Gy) for long course RT. The median planned mTD was similar to the median delivered mTD in the 32 men analysed over the entire course of RT (p=0.84). The mTD did not change significantly over time of planning and delivering RT. The variation in proximity between testes and planning target volume (PTV) was related to within-person variability of mTD in men on the 50th and 75th percentile of mTD and as expected the absolute difference between planned and delivered mTD increased with higher mTD.
  
  
  CONCLUSIONS
  Testicular doses calculated based on plan-CT are an accurate estimation of delivered TD based on repeated cone beam (CB)CT. The within-person variability of TD is related to variation in proximity between testes and PTV in men with moderate to high TD.
authors.affiliation: a Department of Molecular Medicine and Surgery , Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden .
authors.forename: Christian
authors.initials: C
authors.lastname: Buchli
authors.affiliation: b Department of Medical Physics , Karolinska University Hospital , Stockholm , Sweden .
authors.forename: Massoud
authors.initials: M
authors.lastname: Al Abani
authors.affiliation: a Department of Molecular Medicine and Surgery , Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden .
authors.forename: Madelene
authors.initials: M
authors.lastname: Ahlberg
authors.affiliation: a Department of Molecular Medicine and Surgery , Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden .
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Holm
authors.affiliation: c Department of Oncology , Karolinska University Hospital , Stockholm , Sweden .
authors.forename: Tone
authors.initials: T
authors.lastname: Fokstuen
authors.affiliation: d Unit of Biostatistics , Institute of Environmental Medicine, Karolinska Institutet , Stockholm , Sweden , and.
authors.forename: Matteo
authors.initials: M
authors.lastname: Bottai
authors.affiliation: e Department of Oncology-Pathology , Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden.
authors.forename: Jan-Erik
authors.initials: JE
authors.lastname: Frödin
authors.affiliation: b Department of Medical Physics , Karolinska University Hospital , Stockholm , Sweden .
authors.forename: Ingmar
authors.initials: I
authors.lastname: Lax
authors.affiliation: a Department of Molecular Medicine and Surgery , Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden .
authors.forename: Anna
authors.initials: A
authors.lastname: Martling
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D057234:Preoperative Period; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012004:Rectal Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D013737:Testis / Q000528:radiation effects*