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

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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.