The effect of delivering compensating doses on the survival of F10B16 melanoma and 4T1 breast adenocarcinoma treated with prolonged radiation delivery time

�Background: Increasing the complexity in modern radiotherapy techniques have increased the delivery Ɵ me lowering consequently the treatment efficacy. Through simulaƟ ng the delivery Ɵ me delay encountered in such techniques, its’ effect on two cancer cell lines and the compensaƟ ng doses given to prevent such effect was invesƟ gated. Materials and Methods: F10B16 and 4T1 cancer cell lines were exposed to simulated clinical fracƟ onated radiotherapy procedures commonly used in complex techniques. The survival rate of the cells exposed to 2, 4, and 6 Gy of ionizing radiaƟ on with two equal subfracƟ ons given at various Ɵ me intervals between the fracƟ ons (0.25‐4 hours) were determined using the MTT assay. Then, relevant compensaƟ ng doses were calculated and their efficacy in counterbalancing the Ɵ me delay was assessed. Results: The cells’ survival was increased with prolonged treatment Ɵ mes in the fracƟ onated groups being more significant at the lower Ɵ me intervals (up to 2 hours) and for the higher radiosensiƟ ve cells (4T1). Giving the compensated doses decreased the survival of the cells. Conclusion: Delivering appropriate compensaƟ ng doses to the prolonged fracƟ onated groups can counterbalance the effect of Ɵ me delays encountered in complex radiotherapy techniques.