A comparison of the in vivo and in vitro radiation response of three human cervix carcinomas.

The radiation response of three carcinoma of the cervix tumours has been compared in vivo in xenografts using growth delay and in vitro by means of a monolayer-based clonogenic assay. Tumours have been irradiated with 60Co gamma-rays at both high (70-100 cGy/min) and continuous low dose rates (3-5 cGy/min) in order to determine the relative in vivo and in vitro sparing effects associated with lowering radiation dose rate. In vitro, two of the lines (HX155c and HX156c) showed significant low dose rate sparing when compared to the HX160c line (which showed little sparing) (p = 0.012). Despite greater scatter for the in vivo data, there was a general tendency for the in vivo results to follow that predicted from the in vitro experiments. In vivo, HX156 exhibited significant sparing (p = 0.011) whereas HX160 again exhibited no significant sparing (p = 0.15). Although the HX155 line did show some sparing in vivo this did not reach significance (p = 0.111). All three lines showed less actual specific growth delay in vivo than that predicted from in vitro data. These in vitro/in vivo findings lead to the conclusion that rapid predictive testing of radiosensitivity (ideally utilising low dose rate irradiation) would be beneficial in determining the choice of radiotherapy regimens for the treatment of this disease.