title: Fractionated grid therapy in treating cervical cancers: conventional fractionation or hypofractionation?
abstract: OBJECTIVE
  To evaluate the conventionally fractionated and hypofractionated grid therapy in debulking cervical cancers using the linear quadratic (LQ) model.
  
  
  METHODS
  A Monte Carlo technique was used to calculate the dose distribution of a commercially available grid in a 6-MV photon beam. The LQ model was used to evaluate the therapeutic outcome of both the conventionally fractionated (2 Gy/fraction) and hypofractionated (15 Gy/fraction) grid therapy regimens to debulk cervical cancers with different LQ parameters. The equivalent open-field dose (EOD) to the cancer cells and therapeutic ratio (TR) were defined by comparing grid therapy with the open debulking field. The clinical outcomes from 114 patients were used to verify our theoretical model.
  
  
  RESULTS
  The cervical cancer and normal tissue cell survival statistics for grid therapy in two regimens were calculated. The EODs and TRs were derived. The EOD was only a fraction of the prescribed dose. The TR was dependent on the prescribed dose and the LQ parameters of both the tumor and normal tissue cells. The grid therapy favors the acutely responding tumors inside radiosensitive normal tissues. Theoretical model predictions were consistent with the clinical outcomes.
  
  
  CONCLUSIONS
  Grid therapy provided a pronounced therapeutic advantage in both the hypofractionated and conventionally fractionated regimens compared with that seen with single fraction, open debulking field regimens, but the true therapeutic advantage exists only in the hypofractionated grid therapy. The clinical outcomes and our study indicated that a course of open-field radiotherapy is necessary to control tumor growth fully after a grid therapy.
authors.affiliation: Department of Radiation Medicine, The Ohio State University, 300 West 10th Avenue, Columbus, OH 43210-1228, USA. zhang.568@osu.edu
authors.forename: Hualin
authors.initials: H
authors.lastname: Zhang
authors.forename: Jian Z
authors.initials: JZ
authors.lastname: Wang
authors.forename: Nina
authors.initials: N
authors.lastname: Mayr
authors.forename: Xiang
authors.initials: X
authors.lastname: Kong
authors.forename: Jiankui
authors.initials: J
authors.lastname: Yuan
authors.forename: Nilendu
authors.initials: N
authors.lastname: Gupta
authors.forename: Simon
authors.initials: S
authors.lastname: Lo
authors.forename: John
authors.initials: J
authors.lastname: Grecula
authors.forename: Joseph
authors.initials: J
authors.lastname: Montebello
authors.forename: Douglas
authors.initials: D
authors.lastname: Martin
authors.forename: William
authors.initials: W
authors.lastname: Yuh
mesh_terms: D002470:Cell Survival; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D016014:Linear Models; D009010:Monte Carlo Method; D011878:Radiotherapy / Q000295:instrumentation / Q000379:methods; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*