Effect of different fraction interval on tumor control in C57BL mice implanted with Lewis lung cancer

Abstract

Objective To study the effect of different fraction interval with same total radiation dose on tumor growth delay and survival in C57BL mice implanted with lewis lung cancer,and to determine whether prolonged fraction interval will decrease the tumor response to radiation. Methods Forty-eight mice were implanted with lewis lung cancer in the back legs.When the diameter of transplanted tumor reached 0.8 to 1 cm,the mice were randomized into 6 groups:normal control group,single fraction of 18 Gy group,18 Gy in 2 fractions of 9 Gy at 30 min interval group,18 Gy in 7 fractions of 2.57 Gy at 5 min inter val group,18 Gy in 2 fractions of 9 Gy at 60 min interval group and 18 Gy in 7 fractions of 2.57 Gy at 10 rain interval group.The maximal and minimal diameters of the tumor were measured and record every other day to study the tumor growth tendency,the tumor growth delay and the mice survival time. Results The tumor growth delay of groups at prolonged fraction interval was shorter than the group with single fraction of 18 Gy (P 0.05).The mice survival time of the groups with prolonged fraction interval was shortened when omparing to the group with single fraction of 18 Gy.While the difference was not significant between the groups at fraction interval of 30 min and 60 min. Conclusions The pro longed fraction interval but same total radiation dose shortens the tumor growth delay and survival time in the mice implanted with Lewis lung cancer.The longer fraction interval impairs the tumor control more signifi candy.However the difference of the effect on mice survival time is not significant between the groups at fraction interval of 30 min and 60 min. Key words: Lewis lung cancer/irradiation; Fraction interval time; Mouse