Isotoxic radiosurgery planning for brain metastases

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• 作者：Omar Bohoudi ; Anna M.E. Bruynzeel ; Frank J. Lagerwaard ; Johan P. Cuijpers ; Ben J. Slotman ; Miguel A. Palacios ; ^{m.palacios@vumc.nl" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Knowledge-based ; Radiosurgery ; Brain metastases ; Dose prediction ; Brain toxicity
• 刊名：Radiotherapy and Oncology
• 出版年：2016
• 出版时间：August 2016
• 年：2016
• 卷：120
• 期：2
• 页码：253-257
• 全文大小：612 K

文摘

Radionecrosis (RN) has previously been correlated with radiosurgery (RS) dose, lesion volume, and the volume of the brain receiving specific doses, i.e. V_10–14Gy. A knowledge-based individualized estimation of the optimum RS dose has been derived based on lesional volume and brain toxicity parameters.

Methods and materials

A prediction model for brain toxicity parameters and estimation of the optimum RS dose was derived using 30 historical linac-based dynamic conformal arc RS plans for single brain metastases (BM) (0.2–20.3 cc) with risk-adapted dose prescription ranging from 15 to 24 Gy. Derivation of the model followed a three-step process: (1) Derivation of formulas for the prediction of brain toxicity parameters V_10–18Gy; (2) Establishing the relationship of the coefficients used for the prediction of V_12Gy with prescription dose; (3) Derivation of the optimum prescription dose for a given maximum V_12Gy as a function of a given lesion volume. Model validation was performed on 65 new patients with 138 lesions (44 with multiple BM) treated with non-coplanar volumetric modulated stereotactic arc treatment (VMAT).

Results

A linear dependence with the PTV size was found for all investigated brain toxicity parameters (V_10–18Gy). Individualized RS prescription doses can be calculated for any given PTV size based on a linear relationship between V_12Gy and PTV size, according to the formula PD=[V_12Gy+0.96+(1.44×PTV)]/[0.12+(0.12×PTV)]$\text{PD}=[V_{12\text{Gy}}+0.96+(1.44\times \text{PTV})]/[0.12+(0.12\times \text{PTV})]$. A very good correlation (R² = 0.991) was found between the predicted V_12Gy and the resulting V_12Gy in 65 new patients with 138 lesions treated with non-coplanar VMAT technique in our clinic.

Conclusions

A simple formula is proposed for estimation of the optimal individual RS dose for any given lesion volume for patients with (multiple) BM. This formula is based on calculation of the brain toxicity parameter, V_12Gy, for the normal brain minus PTV.