Arrhenius analysis of the thermal response of human colonic adenocarcinoma cells in vitro using the multi-target, single-hit and the linear-quadratic model.

In order to compare the intrinsic thermal sensitivity of different malignant cell lines the multi-target, single-hit model has been widely accepted. It is even applied in clinical hyperthermia by the so-called thermal isoeffect dose (TID) concept originated from this model. The second model which is preferentially used to describe radiation survival curves is the linear-quadratic (LQ) model which can be also applied to thermal response. Interestingly, no breaking point and different activation energies are obtained with this model. In the present paper we demonstrate this discrepancy with the two human colonic adenocarcinoma cell lines WiDr and SW620. Our results further validate the already earlier published persuasion, that neither the multi-target, single-hit model, nor the LQ model are adequate to describe hyperthermic survival. Since both models give completely different results, further data aquisition of isoeffect factors, breaking points and activation enthalpies based on the multi-target, single-hit model only, is unprofitable until advanced models of thermal inactivation have been developed.