Planning issues on linac-based stereotactic radiotherapy

Table 1 The detailed data of 13 representative articles on stereotactic radiotherapy planning

Ref.	Planning issues	Conclusions
Podder et al[5], 2018	Treatment technology	In SBRT treatment of prostate cancer, IMRT/VMAT was superior to 3DCRT/DCAT in terms of target dose conformality and protection of organs at risk
Fernandez et al[21], 2020	Interplay effects	Interplay effects were most evident for large amplitude respirations, complex fields, and small field margins
Tahmasebi et al[22], 2019	Energy	Mixing different ratios of 6 MV and 18 MV X-rays in radiotherapy could fit PDD data equivalent to 6-18 MV energies, thus controlling the incidence of hot spots and better regulating the dose distribution in the target volume
Ruggieri et al[23], 2018	Number of isocenters	Using the novel VMAT technique to perform single-isocenter treatment of multiple intracranial metastases could achieve similar plan quality as multiple-isocenters while significantly reducing treatment time
Tajaldeen et al[24], 2019	Number of fields	In the 3DCRT plans, a minimum of nine beams were used to reduce the dose to the chest wall
Hanna et al[25], 2019	Coplanar/noncoplanar issue	The noncoplanar plans were superior to the coplanar plans in terms of CI of the target volume and protection of healthy brain tissues
Hoffmann et al[26], 2018	The dose calculation algorithm of treatment planning system	Both AcurosXB and MC algorithms had matured to a level where their differences were below the typical experimental detection thresholds for clinical treatment
Younge et al[27], 2017	MLC leaf width	In spinal SBRT, 2.5 mm MLC had limited improvement in planning quality yet increased planning complexity and decreased dose delivery accuracy compared with 5 mm MLC
Ma et al[28], 2019	FFF mode	The FFF mode was fully available for all sizes of clinical fields and had outstanding advantages in reducing treatment time, and predicted a trend of complete replacement of the FF mode by the FFF mode
Duan et al[29], 2020	Auxiliary contours such as ring/shell	When the numbers of peripheral lung cancer SBRT plans shells did not exceed 6, it could consistently improve CI and GI in the target volume and reduce the maximum dose in the spinal cord and V20 and V10 to the bilateral lung
Huq et al[30], 2018	Small field dosimetry	The beam model used to simulate the small field in TPS should pay special attention to the influence of the primary beam source and collimator in the calculation of energy fluence and dose
Snyder Karen et al[31], 2017	Grid size	The use of the 1.5 mm grid size balanced dose accuracy and calculation time
Visak et al[32], 2021	Auto planning	The KBP program reduced the maximum dose of OARs compared to the manual VMAT plans, and each of the planning time was less than 30 min

SRT: Stereotactic radiotherapy; SBRT: Stereotactic body radiotherapy; IMRT: Intensity-modulated radiotherapy; VMAT: Volumetric-modulated arc therapy; 3DCRT: Three-dimensional conformal radiotherapy; DCAT: Dynamic conformal arc therapy; PDD: Percentage depth dose; CI: Conformity index; MC: Monte carlo; MLC: Multi-leaf collimator; FFF: Flattening filter free; GI: Gradient index; V₂₀, V₁₀: Greater than or equal to 20 Gy/10 Gy dose wrap volume as a percentage of total volume; TPS: Treatment planning system; OAR: Organ at risk; KBP: Knowledge-based planning; OARs: Organs at risk.