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

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.

Comparative analysis of dose calculation algorithms for CyberKnife-based stereotactic radiotherapy in lung cancer

“…In the future, we can evaluate the impact of different algorithms on patient clinical outcomes through long-term multi-institutional follow-up observations. Furthermore, utilizing the built-in biological assessment module in TPS, evaluating the impact of different algorithms on tumor control probability (TCP) and normal tissue complications probability (NTCP) in terms of dose differences is considered a future research direction ( 33 , 37 , 38 ). This study can assist radiation oncologists in prospectively understanding the impact of these three algorithms on patient prognosis.…”

Stereotactic radiosurgery for limited brain metastasis using three different techniques: helical tomotherapy, volumetric modulated arc therapy, and cone-based LINAC radiosurgery

“…Another common SRS modality is Gamma-Knife radiosurgery (GK). The outcome from a study conducted in China revealed applicable of Cone-based VMAT in a GK-free RT center [ 18 ]. They retrospectively analyzed dosimetric comparison between GK, Cone-based VMAT, and MLC-based conformal radiotherapy for small single brain metastases.…”

“…They retrospectively analyzed dosimetric comparison between GK, Cone-based VMAT, and MLC-based conformal radiotherapy for small single brain metastases. The result showed better CI and HI, similar GI, but longer beam-on time for GK compared to Cone-based approach [ 18 ].…”

Stereotactic Radiation Therapy of Single Brain Metastases: A Literature Review of Dosimetric Studies

“…The choice of hypofractionation did not correlate with a high metastasis size because some studies used a single fraction even for large targets. Consequently, intervals of BM's size treated with single and three fractions overlapped (0.01-29.18 cc and 10.5-21.4 cc, respectively) [19][20][21][22][23][24][25][26][27][28][29]. which 10 were duplicates.…”

“…The dose and isodose prescriptions lacked homogeneity as well. Nine studies used SRS [21][22][23][24][25][26][27][28][29] and only two studies used HF-SRT [19,20]. The choice of hypofractionation did not correlate with a high metastasis size because some studies used a single fraction even for large targets.…”