Preliminary study and establishment of LQB model and qLQB model for radiation-induced lung injury / 中华放射肿瘤学杂志

Objective To build two mathematical models, named LQB model and quantified LQB ( qLQB) model, based on the LQ model, and to test their effectiveness in evaluation of radiation?induced lung injury using the Lyman?Kutcher?Burman ( LKB) model. Methods Firstly, a qualitative LQB model was established. Forty?five patients with thoracic cancer were enrolled as subjects. For each patient, two plans were designed using ELEKTA Precise 2. 12 treatment planning system. The plans preferred by the qualitative LQB model and the LKB model were compared. Secondly, a qLQB model was established based on the LQB model. The model was used to calculate the percentage of radiation pneumonitis (RP) for the 45 plans obtained in the first step. Comparison between the percentage of RP and normal tissue complication probability (NTCP) calculated by the LKB model was made by paired t test. Results In the plans for 45 patients, the coincidence rate of the qualitative LQB model with the LKB model was 96%(43/46). For the 45 plans preferred by the LKB model, there was no difference between the percentage of RP by the qLQB model and the NTCP by the LKB model ( P=0. 412) . Conclusions The LQB model and the qLQB model are in good accordance with the LKB model in plan preference and evaluation of radiation?induced lung injury.

BIOLOGICAL BASIS OF TIME,DOSE AND FRACTIONATION IN FRACTIONATED RADIOTHERAPY / 中华放射肿瘤学杂志

The biology rationale for radiotherapy in the treatment of malignant disease is based on repair, repopulation,reoxygenation and cell cycle redistribution. Various aspects of the roles of the 4R' are discussed, including in determining the sensitivity of tumors and normal tissue tolerances. An improvement in therapeutic ratio may derive from reducing the dose per fraction and minimizing the overall treatmemt duration. Some methods have developed to predict the response of normal and tumor tissues before radiotherapy. The parameters of cell survival at 2Gy(SF2) was correlated with clinical outcome. There is reasons to suppose that the pretreatment tumor LI and Tpot mat be good predictors for tumor repopulation kinetics. This review also discussed the rationale for the use of LQ model in fractionated radiotherapy.