Purpose: To propose a novel treatment approach, designated VMAT+, involving addition of <5 IMRT beams with computer-optimized non-coplanar orientations to VMAT, and evaluate it for liver Stereotactic Body Radiation Therapy (SBRT). VMAT+ is investigated as an alternative for (1) coplanar VMAT and (2) multi-beam non-coplanar treatment. Methods/materials: For fifteen patients with liver metastases, VMAT+ plans were compared with (1) dual-arc VMAT and (2) 25-beam, non-coplanar treatment with computer-optimized beam orientations (25-NCP). All plans were generated fully automatically for delivery of the highest feasible tumor Biologically Effective Dose (BED). OAR doses, intermediate-dose-spillage, dose-compactness, and measured delivery times were evaluated. Results: With VMAT+ the maximum achievable tumor BED was equal to that of 25-NCP. Conversely, VMAT resulted in a lower tumor BED in 5 patients. Compared to VMAT, VMAT+ yielded significant dose reductions in OARs. Intermediate-dose-spillage and dose-compactness were significantly improved by 9.8% and 17.3% (p ≤. 0.002), respectively. Treatment times with VMAT+ were only enhanced by 4.1. min on average, compared to VMAT (8.4. min). Improvements in OAR sparing with 25-NCP, compared to VMAT+, were generally modest and/or statistically insignificant, while delivery times were on average 20.5. min longer. Conclusions: For liver SBRT, VMAT+ is equivalent to time-consuming treatment with 25 non-coplanar beams in terms of achievable tumor BED. Compared to VMAT, OAR sparing and intermediate-dose-spillage are significantly improved, with minor increase in delivery time.

Additional Metadata
Keywords Automated planning, Beam angle optimization, IMRT, Liver SBRT, Non-coplanar, VMAT
Persistent URL dx.doi.org/10.1016/j.radonc.2017.02.018, hdl.handle.net/1765/98856
Journal Radiotherapy & Oncology
Citation
Sharfo, A.W.M, Dirkx, M.L.P, Breedveld, S, Romero, A.M, & Heijmen, B.J.M. (2017). VMAT plus a few computer-optimized non-coplanar IMRT beams (VMAT+) tested for liver SBRT. Radiotherapy & Oncology, 123(1), 49–56. doi:10.1016/j.radonc.2017.02.018