title: Predictive factors of rectal toxicity after permanent iodine-125 seed implantation: Prospective cohort study in 2339 patients.
abstract: To evaluate the incidence and the associated factors of rectal toxicity in patients with prostate cancer undergoing permanent seed implantation (PI) with or without external beam radiation therapy (EBRT) in a nationwide prospective cohort study in Japan (J-POPS) during the first 2 years.
  
  
  
  A total of 2,339 subjects were available for the analyses. Rectal toxicity was evaluated using the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0.
  
  
  
  The 3-year cumulative incidence for grade ≥2 rectal toxicity was 2.88%, 1.76%, and 6.53% in all subjects, PI group and EBRT combination therapy group, respectively. On multivariate analysis, among all subjects, grade ≥2 rectal toxicity was associated with rectal volumes receiving 100% of the prescribed dose (R100; p < 0.0001) and EBRT combination therapy (p = 0.0066). R100in the PI group (p = 0.0254), and R100(p = 0.0011) and interactive planning (p = 0.0267) in the EBRT combination therapy group were also associated with grade ≥2 toxicity. The 3-year cumulative incidence of grade ≥2 rectal toxicity was 3.80% and 1.37% for R100≥ 1 mL and R100< 1 mL, respectively, in the PI group (p = 0.0068), and 14.09% and 5.52% for R100≥ 1 mL and R100< 1 mL, respectively, in the EBRT combination therapy group (p = 0.0070).
  
  
  
  Rectal toxicity was relatively rare in this study compared with previous reports. For Japanese prostate cancer patients, R100< 1 mL in both PI and EBRT combination therapy groups and interactive planning in EBRT combination therapy group may be effective in decreasing the incidence of rectal toxicity.
authors.affiliation: Department of Radiology, Okayama University Graduate School of Medicine, Okayama, Japan. Electronic address: n-katayama@bea.hi-ho.ne.jp.
authors.forename: Norihisa
authors.initials: N
authors.lastname: Katayama
authors.affiliation: Department of Radiation Oncology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.
authors.forename: Atsunori
authors.initials: A
authors.lastname: Yorozu
authors.affiliation: Translational Research Informatics Center, Kobe, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Maruo
authors.affiliation: Translational Research Informatics Center, Kobe, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Kojima
authors.affiliation: Department of Radiation Oncology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Ohashi
authors.affiliation: Department of Urology, Nara Medical University School of Medicine, Nara, Japan.
authors.forename: Nobumichi
authors.initials: N
authors.lastname: Tanaka
authors.affiliation: Translational Research Informatics Center, Kobe, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikuchi
authors.affiliation: Translational Research Informatics Center, Kobe, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Higashide
authors.affiliation: Department of Urology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Saito
authors.affiliation: Department of Radiology, Kyoundo Hospital, Tokyo, Japan.
authors.forename: Takushi
authors.initials: T
authors.lastname: Dokiya
authors.affiliation: Translational Research Informatics Center, Kobe, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Fukushima
authors.affiliation: Institutes of Preventive Medicine, Kurosawa Hospital, Takasaki, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Yamanaka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D015994:Incidence; D007457:Iodine Radioisotopes / Q000009:adverse effects* / Q000627:therapeutic use; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000453:epidemiology* / Q000209:etiology; D012007:Rectum / Q000528:radiation effects*; D012307:Risk Factors
chemical_list: D007457:Iodine Radioisotopes
keywords: Brachytherapy; Dose-volume histogram parameters; External beam radiation therapy; Interactive planning; Prostate cancer; Rectal toxicity