Clinical Feasibility of Using Single-isocentre Non-coplanar Volumetric Modulated Arc Therapy Combined with Non-coplanar Cone Beam Computed Tomography in Hypofractionated Stereotactic Radiotherapy for Five or Fewer Multiple Intracranial Metastases

• Published in: Clinical oncology (Royal College of Radiologists (Great Britain)) 2023-06, Vol.35 (6), p.408-416
• Main Authors: Lai, J.L., Liu, S.P., Liu, J., Li, X.K., Chen, J., Jia, Y.M., Lei, K.J., Zhou, L.
• Format: Article
• Language: English
• Subjects: Brain Neoplasms - diagnostic imaging; Brain Neoplasms - radiotherapy; Brain Neoplasms - secondary; Cone-Beam Computed Tomography; Feasibility Studies; Humans; Hypofractionated stereotactic radiotherapy; multiple brain metastases; non-coplanar cone beam computed tomography; plan quality; Radiosurgery - methods; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy, Intensity-Modulated - methods; set-up accuracy
• ISSN: 0936-6555; 1433-2981
• DOI: 10.1016/j.clon.2023.03.011

To evaluate the clinical feasibility of single-isocentre non-coplanar volumetric modulated arc therapy (NC-VMAT) with non-coplanar cone beam computed tomography (NC-CBCT) in hypofractionated stereotactic radiotherapy (HSRT) for five or fewer multiple brain metastases. Ten patients with multiple brain metastases who underwent single-isocentre NC-VMAT HSRT with limited couch rotations (within ±45°) and NC-CBCT with a limited scanning range (150–200°) were included in the current analysis. Conventional single-isocentre coplanar VMAT (C-VMAT) plans were generated and compared with NC-VMAT plans. The intracranial response and toxicities of single-isocentre NC-VMAT HSRT were also evaluated. Compared with C-VMAT, NC-VMAT generated better target conformity (P < 0.05), a lower gradient index (P < 0.05) and better normal brain tissue sparing, especially for volume ≥12 Gy, with a median reduction of 12.65 cm3. For 45° couch rotation, NC-CBCT produced sufficient image quality to differentiate bony anatomy, even with a 150° scanning range, which could be successfully used for patient set-up correction. After NC-CBCT, 57.1% of the measured non-coplanar set-up errors exceeded the threshold value. The median gamma passing rate of NC-VMAT was higher than that of C-VMAT plans (P < 0.05). The non-coplanar beam of NC-VMAT with NC-CBCT corrections exhibited superior gamma passing rate to that without NC-CBCT corrections. The intracranial objective response rate and disease control rate for all patients were 80% (8/10) and 100% (10/10), respectively, and the most common toxicities were headache (20%) and dizziness (20%). NC-VMAT with limited couch rotation (within ±45°) combined with NC-CBCT with a limited scanning range (150–200°) markedly improves the plan quality and set-up accuracy in single-isocentre multiple-target HSRT. •Non-coplanar CBCT with limited scanning range could achieve set-up error correction at non-zero couch angle in multiple-target HSRT.•57.1% of the measured non-coplanar set-up errors exceeded the preset tolerance of 0.5 mm/0.5°in multiple-target HSRT.•HSRT delivered by single-isocentre non-coplanar VMAT with limited couch rotations could bring dosimetric advantages over coplanar VMAT.•Non-coplanar CBCT corrections could generate better dose delivery accuracy to HSRT with non-coplanar VMAT, demonstrated by high-resolution SRS MapCHECK®.