title: Modelling second malignancy risks from low dose rate and high dose rate brachytherapy as monotherapy for localised prostate cancer.
abstract: To estimate the risks of radiation-induced rectal and bladder cancers following low dose rate (LDR) and high dose rate (HDR) brachytherapy as monotherapy for localised prostate cancer and compare to external beam radiotherapy techniques.
  
  
  
  LDR and HDR brachytherapy monotherapy plans were generated for three prostate CT datasets. Second cancer risks were assessed using Schneider's concept of organ equivalent dose. LDR risks were assessed according to a mechanistic model and a bell-shaped model. HDR risks were assessed according to a bell-shaped model. Relative risks and excess absolute risks were estimated and compared to external beam techniques.
  
  
  
  Excess absolute risks of second rectal or bladder cancer were low for both LDR (irrespective of the model used for calculation) and HDR techniques. Average excess absolute risks of rectal cancer for LDR brachytherapy according to the mechanistic model were 0.71 per 10,000 person-years (PY) and 0.84 per 10,000 PY respectively, and according to the bell-shaped model, were 0.47 and 0.78 per 10,000 PY respectively. For HDR, the average excess absolute risks for second rectal and bladder cancers were 0.74 and 1.62 per 10,000 PY respectively. The absolute differences between techniques were very low and clinically irrelevant. Compared to external beam prostate radiotherapy techniques, LDR and HDR brachytherapy resulted in the lowest risks of second rectal and bladder cancer.
  
  
  
  This study shows both LDR and HDR brachytherapy monotherapy result in low estimated risks of radiation-induced rectal and bladder cancer. LDR resulted in lower bladder cancer risks than HDR, and lower or similar risks of rectal cancer. In absolute terms these differences between techniques were very small. Compared to external beam techniques, second rectal and bladder cancer risks were lowest for brachytherapy.
authors.affiliation: Departments of Radiotherapy and Medical Physics, St James's Institute of Oncology, UK; University of Leeds, UK.
authors.forename: Louise
authors.initials: L
authors.lastname: Murray
authors.affiliation: Departments of Radiotherapy and Medical Physics, St James's Institute of Oncology, UK.
authors.forename: Joshua
authors.initials: J
authors.lastname: Mason
authors.affiliation: Departments of Radiotherapy and Medical Physics, St James's Institute of Oncology, UK; University of Leeds, UK. Electronic address: a.henry@leeds.ac.uk.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Henry
authors.affiliation: Mount Vernon Cancer Centre, Northwood, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Hoskin
authors.affiliation: Klinik fur Strahlentherapie, Kiel, Germany.
authors.forename: Frank-Andre
authors.initials: FA
authors.lastname: Siebert
authors.affiliation: Institute Verbeeten, Tilburg, Netherlands.
authors.forename: Jack
authors.initials: J
authors.lastname: Venselaar
authors.affiliation: Departments of Radiotherapy and Medical Physics, St James's Institute of Oncology, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Bownes
mesh_terms: D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008297:Male; D008954:Models, Biological; D009381:Neoplasms, Radiation-Induced / Q000209:etiology*; D016609:Neoplasms, Second Primary / Q000209:etiology* / Q000473:pathology; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012004:Rectal Neoplasms / Q000209:etiology*; D012007:Rectum / Q000528:radiation effects; D012306:Risk; D014057:Tomography, X-Ray Computed / Q000379:methods; D001743:Urinary Bladder / Q000528:radiation effects; D001749:Urinary Bladder Neoplasms / Q000209:etiology*
keywords: High dose rate brachytherapy; Localised prostate cancer; Low dose rate brachytherapy; Second cancer risks