Hypersensitivity to low single doses and split-dose recovery: two manifestations of induced resistance that might be related

Purpose: To study retrospectively the relationship between intrinsic radiosensitivity (SF2), and both the low-dose inducible response (alphas/alphar) and the amount of split-dose recovery (betaRR). Materials and methods: A total of 53 sets of experimental data obtained with 44 human cell lines were collected from the literature and the above relationships were studied. Results: Analysis showed a statistically significant correlation between alphas/alphar and SF2 (p = 0.0023, 10 sets of data), and a statistically significant inverse correlation between betaRR and SF2 (p = 0.0005, 36 sets of data, AT excluded). Furthermore, the analysis of the relationship between the challenge dose SF2 (after a clinical-sized priming dose) and that of the single-dose SF2 (27 sets of data, AT excluded) showed a statistically significant correlation (p < 0.0001), which deviates from, and becomes higher than, the one-to-one relationship for single-dose SF2 < 0.30, suggesting that the final response to fractionated irradiation...