Fractionated grid therapy in treating cervical cancers: conventional fractionation or hypofractionation?
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.
Zhang
Hualin
H
Department of Radiation Medicine, The Ohio State University, 300 West 10th Avenue, Columbus, OH 43210-1228, USA. zhang.568@osu.edu
Wang
Jian Z
JZ
Mayr
Nina
N
Kong
Xiang
X
Yuan
Jiankui
J
Gupta
Nilendu
N
Lo
Simon
S
Grecula
John
J
Montebello
Joseph
J
Martin
Douglas
D
Yuh
William
W
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*