title: Preliminary analysis of risk factors for late rectal toxicity after helical tomotherapy for prostate cancer.
abstract: The purpose of this study is to examine risk factors for late rectal toxicity for localized prostate cancer patients treated with helical tomotherapy (HT). The patient cohort of this retrospective study was composed of 241 patients treated with HT and followed up regularly. Toxicity levels were scored according to the Radiation Therapy Oncology Group grading scale. The clinical and dosimetric potential factors increasing the risk of late rectal toxicity, such as age, diabetes, anticoagulants, prior abdominal surgery, prescribed dose, maximum dose of the rectum, and the percentage of the rectum covered by 70 Gy (V70), 60 Gy (V60), 40 Gy (V40) and 20 Gy (V20) were compared between ≤ Grade 1 and ≥ Grade 2 toxicity groups using the Student's t-test. Multivariable logistic regression analysis of the factors that appeared to be associated with the risk of late rectal toxicity (as determined by the Student's t-test) was performed. The median follow-up time was 35 months. Late Grade 2-3 rectal toxicity was observed in 18 patients (7.4%). Age, the maximum dose of the rectum, V70 and V60 of the ≥ Grade 2 toxicity group were significantly higher than in those of the ≤ Grade 1 toxicity group (P = 0.00093, 0.048, 0.0030 and 0.0021, respectively). No factor was significant in the multivariable analysis. The result of this study indicates that the risk of late rectal toxicity correlates with the rectal volume exposed to high doses of HT for localized prostate cancer. Further follow-up and data accumulation may establish dose-volume modeling to predict rectal complications after HT.
authors.affiliation: Department of Radiation Oncology, Aichi Cancer Center Hospital, 1-1 Kanokoden, Chikusaku, Nagoya 464-8681, Japan.
authors.forename: Natsuo
authors.initials: N
authors.lastname: Tomita
authors.forename: Norihito
authors.initials: N
authors.lastname: Soga
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ogura
authors.forename: Norio
authors.initials: N
authors.lastname: Hayashi
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Shimizu
authors.forename: Takashi
authors.initials: T
authors.lastname: Kubota
authors.forename: Junji
authors.initials: J
authors.lastname: Ito
authors.forename: Kimiko
authors.initials: K
authors.lastname: Hirata
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Ohshima
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tachibana
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kodaira
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D015897:Comorbidity; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D007674:Kidney Diseases / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000453:epidemiology*; D020266:Radiotherapy, Conformal / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D012307:Risk Factors; D015996:Survival Rate
keywords: helical tomotherapy; image-guided radiation therapy; intensity-modulated radiation therapy; late toxicity; prostate cancer