title: In vitro determination of radiation sensitivity parameters for DU-145 prostate cancer cells.
abstract: OBJECTIVE
  The prolonged delivery times associated with intensity modulated radiation therapy (IMRT) may reduce treatment effectiveness of radiation therapy for cancers with short repair half-times. In this study, in vitro radiation experiments with DU-145 prostate cancer cells were designed to quantify the half-time of sublethal damage repair.
  
  
  METHODS
  A series of single-fraction and split-dose clonogenic survival experiments were performed and analyzed using the linear-quadratic (LQ) survival model with mono-/two-component exponential and reciprocal-time repair kinetic models.
  
  
  RESULTS
  Our data indicate that DU-145 cells are very radiosensitive (alpha = 0.44 Gy(-1), standard CI: 0.41-0.49 Gy(-1)) and are relatively insensitive to dose fractionation (alpha/beta = 16 Gy, standard CI: 12-34 Gy). The estimated repair half-time is 23 min (standard CI: 10-97 min) with some evidence that a small portion of the sublethal damage is repaired more slowly.
  
  
  CONCLUSIONS
  The reported radiosensitivity parameters (alpha and alpha/beta) are larger than those derived from other in vitro experiments and clinical data. In contrast, the half-time for sublethal damage repair ( approximately 23 min) is close to the one derived from clinical data ( approximately 16 min). For such short repair half-times, the effectiveness of IMRT treatments may be substantially improved by decreasing the fraction delivery time.
authors.affiliation: Department of Radiation Medicine, The Ohio State University, Columbus, Ohio 43210, USA. wang.993@osu.edu
authors.forename: Jian Z
authors.initials: JZ
authors.lastname: Wang
authors.forename: Juong G
authors.initials: JG
authors.lastname: Rhee
authors.forename: Peipei
authors.initials: P
authors.lastname: Shi
authors.forename: Robert D
authors.initials: RD
authors.lastname: Stewart
authors.forename: X
authors.initials: X
authors.lastname: Allen Li
mesh_terms: D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D050397:Radiotherapy, Intensity-Modulated