Demonstration of Bystander Response in High Dose Technique of Grid Using Theoretical Calculation by Linear Quadratic Model Along With Experimental Investigations Publisher



Pakniyat F¹ ; Gholami S² ; Nedaie HA^{1, 2} ; Mozdarani H³ ; Mahmoudzadeh A⁴ ; Salimi M⁵ Show Affiliations
Source: International Journal of Radiation Research Published:2020

Abstract

Background: The Linear Quadratc (LQ) equaton as the most common formula in radiotherapy has a debatable accuracy in modeling high-dose effects. The purpose of this study was to demonstrate bystander response of the Grid treatment in SCC cell line, based on both theoretcal calculatons and experimental investgatons. Materials and methods: The linear quadratc model was used to calculate the equivalent uniform dose (EUD) of a Grid-field with the 10 Gy maximum doses. According to the EUD definiton, the identcal tumor survival fracton (SF) was expected to obtain from both Grid and open-field single fracton. After observing the difference, the clonogenic and apoptosis assays were exerted to investgate bystander response via medium transfer strategy which was performed from 10Gy-irradiated donors to 1.5Gy-irradiated recipients. Results: The EUD was equal to 4 Gy and the SF of 4 Gy EUD and 10 Gy Grid-field were 0.1 ± 0.02 and 0.051 ± 0.008, respectvely. These findings contradicted the theoretcal expectatons of their survivals equality. Moreover, the bystander clonogenic cells death enhanced approximately by 2.91 tmes (statstcally significant); highlightng the bystander response role. The apoptotc findings illustrated that the bystander cells experienced an approximately 10% increase and the apoptotc rate confirmed the clonogenic survival result which was less in the EUD than the Grid-field. Conclusion: Since the SF of the Grid-field was less than the EUD, it revealed the Grid therapeutc advantages plus bystander response manifestaton; that was ignored in the LQ equaton and may not be demonstrated by sheer theoretcal calculatons of the modulated-field. © 2020 Novin Medical Radiation Institute. All rights reserved.