title: The application of the linear quadratic model to compensate the effects of prolonged fraction delivery time on a Balb/C breast adenocarcinoma tumor: An in vivo study.
abstract: Purpose To investigate the effect of increasing the overall treatment time as well as delivering the compensating doses on the Balb/c breast adenocarcinoma (4T1) tumor. Materials and methods A total of 72 mice were divided into two aliquots (classes A and B) based on the initial size of their induced tumor. Each class was divided into a control and several treatment groups. Among the treatment groups, group 1 was continuously exposed to 2 Gy irradiation, and groups 2 and 3 received two subfractions of 1 Gy over the total treatment times of 30 and 60 min, respectively. To investigate the effect of compensating doses, calculated based on the developed linear quadratic model (LQ) model, the remaining two groups (groups 4 and 5) received two subfractions of 1.16 and 1.24 Gy over the total treatment times of 30 and 60 min, respectively. The growing curves, Tumor Growth Time (TGT), Tumor Growth Delay Time (TGDT) and the survival of the animals were studied. Results For class A (tumor size ≤ 30 mm(3)), the average tumor size in the irradiated groups 1-5 was considerably different compared to the control group as one unit (day) change in time, by amount of -160.8, -158.9, +39.4 and +44.0, respectively. While these amounts were +22.0, +17.9, -21.7 and -0.1 for class B (tumor size ≥ 400 mm(3)). For the class A of animals, the TGT and TGDT parameters were significantly lower (0 ≤ 0.05) for the groups 2 and 3, compared to group 1. There was no significant difference (p > 0.05) between groups 1, 4 and 5 in this class. There was no significant difference (p > 0.05) between all the treated groups in class B. Conclusions Increasing total treatment time affects the radiobiological efficiency of treatment especially in small-sized tumor. The compensating doses derived from the LQ model can be used to compensate the effects of prolonged treatment times at in vivo condition.
authors.affiliation: a Department of Medical Physics, Faculty of Medical Sciences , Tarbiat Modares University , Tehran, Iran ;|b Department of Medical Physics, Faculty of Medicine , Hamadan University of Medical Sciences , Hamadan , Iran ;
authors.forename: Safoora
authors.initials: S
authors.lastname: Nikzad
authors.affiliation: a Department of Medical Physics, Faculty of Medical Sciences , Tarbiat Modares University , Tehran, Iran ;
authors.forename: Bijan
authors.initials: B
authors.lastname: Hashemi
authors.affiliation: c Department of Immunology , Faculty of Medical Sciences, Tarbiat Modares University , Tehran , Iran ;
authors.forename: Zuhair Saraf
authors.initials: ZS
authors.lastname: Hasan
authors.affiliation: d Department of Medical Genetics, Faculty of Medical Sciences , Tarbiat Modares University , Tehran , Iran ;
authors.forename: Hossein
authors.initials: H
authors.lastname: Mozdarani
authors.affiliation: e Department of Medical Physics and Medical Engineering & Medical Student's Research Center, School of Medicine , Isfahan University of Medical Sciences , Isfahan , Iran ;|f Department of Medical Radiation Engineering, Faculty of Advanced Sciences & Technologies , Isfahan University , Isfahan , Iran ;
authors.forename: Milad
authors.initials: M
authors.lastname: Baradaran-Ghahfarokhi
authors.affiliation: g Department of Biostatistics , Hamadan University of Medical Sciences , Hamadan , Iran.
authors.forename: Payam
authors.initials: P
authors.lastname: Amini
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology* / Q000532:radiotherapy*; D000818:Animals; D001943:Breast Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D003198:Computer Simulation; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D016014:Linear Models; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome
keywords: Intensity Modulated Radiation Therapy (IMRT); breast adenocarcinoma; compensating dose; fractionation; tumor size