Dosimetric Comparison, Treatment Efficiency Estimation, and Biological Evaluation of Popular Stereotactic Radiosurgery Options in Treating Single Small Brain Metastasis.

Yanhua Duan,Yinghui Wu,Dong Liu,Yan Shao,Boheng Wu,Xiaolong Fu,Yang Lin,Qing Kong,Hong Fu,Hongbin Cao,Aihui Feng,Ying Huang,Hao Wang,Hengle Gu,Kui Ma,Hua Chen,Zhiyong Xu,Lijun Zhou

doi:10.3389/fonc.2021.716152

Abstract

ObjectivesThis study aimed to show the advantages of each stereotactic radiosurgery (SRS) treatment option for single small brain metastasis among Gamma Knife (GK), Cone-based VMAT (Cone-VMAT), and MLC-based CRT (MLC-CRT) plans.Materials and MethodsGK, Cone-VMAT, and MLC-CRT SRS plans were retrospectively generated for 11 patients with single small brain metastasis whose volume of gross tumor volume (GTV) ranged from 0.18 to 0.76 cc (median volume 0.60 cc). Dosimetric parameters, treatment efficiency, and biological parameters of the three techniques were compared and evaluated. The metric variation with the planning target volume (PTV) was also studied.ResultsThe conformity index (CI) was similar in GK and MLC-CRT plans, higher than Cone-VMAT. Cone-VMAT achieved comparable volume covered by 12 Gy (V12) and gradient index (GI) as GK, lower than MLC-CRT. The heterogeneity index (HI) of GK, Cone-VMAT, and MLC-CRT decreased sequentially. GK gave the lowest volume covered by 3 Gy (V3) and 6 Gy (V6), while MLC-CRT got the highest. The beam-on time and treatment time of GK, Cone-VMAT, and MLC-CRT decreased in turn. Tumor control probability (TCP) of all three SRS plans was greater than 98%, and normal tissue complication probability (NTCP) of all organs at risk (OARs) was below 0.01%. GK and Cone-VMAT resulted in superior TCP and NTCP of the normal brain tissue than MLC-CRT. The relative value of Cone-VMAT and GK for all metrics hardly changed with the target volume. Except for the unchanged HI and TCP, the other results of MLC-CRT with respect to GK improved as the target volume increased. MLC-CRT could produce higher CI than GK and Cone-VMAT when the target volume increased above 2 and 1.44 cc, respectively.ConclusionFor single small brain metastases, Cone-VMAT may be used as an alternative to GK-free centers. In addition to the advantage of short treatment time, MLC-CRT showed superiority in CI as the target volume increased. Treatment centers can choose appropriate SRS technique on a case-by-case basis according to institutional conditions and patients’ individual needs.

Highlights

Brain metastasis is one of the most common brain tumors, and its morbidity and mortality are very high [1]
multileaf collimator (MLC)-CRT resulted in a similar conformity index (CI) to Gamma Knife (GK) for single small brain metastasis, and Cone-VMAT could compete with GK in terms of V12, gradient index (GI), TCP, and NTCP of the brain
This study provides useful dosimetric, treatment efficiency, and biological insights of GK, Cone-VMAT, and MLC-CRT for single small brain metastasis

Summary

Introduction

Brain metastasis is one of the most common brain tumors, and its morbidity and mortality are very high [1]. The development of radiotherapy enables stereotactic radiosurgery (SRS) to deliver high doses to brain metastases through a single fraction, giving the tumor ablative dose while minimizing organs at risk (OARs) damage. SRS can achieve a similar curative effect as surgery [3, 4]. The introduction of Gamma Knife (GK) has made SRS a common treatment for small brain tumors (diameter

Objectives

Methods

Results

Discussion

Conclusion