Department of Radiation Oncology, University of California San Francisco (UCSF), San Francisco, CA, USA.
Department of Neurosurgery, University of California San Francisco (UCSF), San Francisco, CA, USA.
Acta Neurochir Suppl. 2021;128:101-106. doi: 10.1007/978-3-030-69217-9_10.
The present proof-of-principle study investigated radiobiological effects of redistributing central target dose hot spots across different treatment fractions during hypofractionated stereotactic radiosurgery (HSRS) of large intracranial tumors.
Redistribution of central target dose hot spots during HSRS was simulated, and its effects were evaluated in eight cases of brain metastases. To assess dose variations in the target across N number of treatment fractions, a generalized biologically effective dose (gBED) was formulated. The gBED enhancement ratio was defined as the ratio of gBED in the tested treatment plan (with central target dose hot spot redistributions across fractions) to gBED in the conventional treatment plan (without central target dose hot spot redistributions).
At a median α value of 0.3/Gy, the tested treatment plans resulted in average gBED increases of 15.6 ± 3.5% and 8.3 ± 1.8% for α/β ratios of 2 and 10 Gy, respectively. In comparison with conventional treatment plans, the differences in the Paddick conformity index and gradient index did not exceed 2%.
Redistributing central target dose hot spots across different treatment fractions during HSRS may be considered promising for enhancing gBED in the target. It may be beneficial for management of large intracranial neoplasms; thus, it warrants further clinical testing.
本原理验证研究调查了在大颅内肿瘤的立体定向放射外科（HSRS）中，在分次治疗过程中重新分配中央靶区热点的放射生物学效应。
模拟了 HSRS 过程中中央靶区热点的重新分布，并在 8 例脑转移瘤中评估了其效果。为了评估目标在 N 个治疗分次中的剂量变化，制定了广义生物有效剂量（gBED）。gBED 增强比定义为测试治疗计划（中央靶区剂量热点跨分次重新分布）的 gBED 与常规治疗计划（无中央靶区剂量热点重新分布）的 gBED 之比。
在中位α值为 0.3/Gy 时，对于α/β比为 2 和 10 Gy 的情况，测试治疗计划分别导致平均 gBED 增加 15.6±3.5%和 8.3±1.8%。与常规治疗计划相比，Paddick 适形指数和梯度指数的差异不超过 2%。
在 HSRS 过程中，在不同的分次治疗中重新分配中央靶区热点，可能有助于提高靶区的 gBED。这可能有益于大颅内肿瘤的管理，因此值得进一步的临床测试。
