転移性脳腫瘍に対するLQモデルに基づく分割照射方法の効果比較

Abstract

The Biologically Effective Dose (BED) based on the linear quadratic (LQ) model is often used for evaluating the effect of fraction size and total dose in fractionated radiotherapy ; however, it has recently been suggested that the BED is not always available for stereotactic irradiation (STI). In the present study, we analyzed the relationship between the different fractionation schedules and the efficacy of STI for metastatic brain tumors using the LQ model. The BED for each prescribed dose was calculated in stereotactic radiosurgery and stereotactic radiation therapy, and the tumor volume was evaluated using MRI images acquired during the follow-up after the irradiation. The cumulative probabilities of partial response rates (PRR) and disease control rates (DCR) were estimated as a function of the day after the initial treatment using the Kaplan-Meier method. Comparisons among the groups were accomplished using a log-rank test. SRS showed a significantly better PRR and DCR compared with SRT using a fraction size of 4Gy or less (p=0.0193 and p=0.0193, respectively). A single high dose radiation therapy has been suggested to be more effective than that predicted by the LQ model.