In Vitro Radiosensitivity of Six Human Cell Lines: A Comparative Study with Different Statistical Models

Abstract

The intrinsic radiosensitivity of human cell lines (5 tumor and one nontransformed fibroblastic) was studied in vitro. The survival curves were fitted by the single-hit multitarget, the 2-hit multitarget, the single-hit multitarget with initial slope and the quadratic models. A statistical test (comparison of variances left unexplained by the 4 models) and a biological consideration (check for independence of the fitted parameters vis-a-vis the portion of the survival curve in question) were carried out. The quadratic model was best with each test. Since the quadratic model described the low-dose effects, revealing a single-hit lethal component, and the 6 survival curves displayed a continuous curvature, the target models and the widely used linear regression were ruled out. With the quadratic model the parameters of the 6 cell lines were calculated. The intrinsic radiosensitivity varies greatly among the different cell lines; the interpretation of the fibroblast survival curve is basically not different from the tumor cell lines; and the radiosensitivity of these human cell lines is comparable to that of other mammalian cell lines.