Hypofractionated stereotactic radiotherapy for large brain metastases: Optimizing the dosimetric parameters

Area of Science:

• Radiation Oncology
• Neurosurgery
• Medical Physics

Background:

• Stereotactic radiotherapy is a cornerstone in managing brain metastases (BM).
• Hypofractionated stereotactic radiotherapy (HFSRT) is increasingly used for larger BM.
• Optimizing treatment plans is crucial for maximizing efficacy and minimizing toxicity.

Purpose of the Study:

• To compare the dosimetric performance of four HFSRT planning techniques for large brain metastases (BM).
• To evaluate volumetric modulated arc therapy (VMAT) against dynamic conformal arcs (DCA).
• To assess target coverage, organ-at-risk sparing, and dose distribution.

Main Methods:

• Ten patients with single, large BM (≥25mm diameter) treated with NovalisTx® DCA HFSRT were retrospectively analyzed.
• Three VMAT techniques were evaluated: VMATc_Eclipse® (coplanar), VMATnc_Eclipse® (non-coplanar), and VMATnc_Elements® (non-coplanar).
• Prescribed dose: 23.1Gy in three fractions; PTV marginal dose at 70% isodose.

Main Results:

• All VMAT techniques demonstrated superior conformity indices compared to DCA (1.05 vs 1.28, P<0.05).
• VMATnc_Elements® and DCA showed better gradient indices (2.43 vs 3.02, P<0.001).
• VMAT techniques significantly reduced high-dose delivery to healthy brain tissue (5.6-6.3 cc vs 9.4 cc, P<0.001) and low-dose spillage (V5Gy) compared to DCA.

Conclusions:

• NovalisTx® VMAT HFSRT for large BM (≥25mm) offers an improved dosimetric profile.
• VMAT provides a better balance of target coverage, healthy tissue sparing, and reduced low-dose delivery versus DCA.
• Non-coplanar VMAT techniques may offer further advantages in specific dosimetric parameters.