Improving efficiency in the radiation management of multiple brain metastases using a knowledge‐based planning solution for single‐isocentre volumetric modulated arc therapy (VMAT) technique

Abstract

Introduction: This study aimed to develop a single-isocentre volumetric modulated arc therapy (si-VMAT) technique for multiple brain metastases using knowledge-based planning software, comparing it with a multipleisocentre stereotactic radiosurgery (mi-SRS) planning approach. Methods: Twenty-six si-VMAT plans were created and uploaded into RapidPlan TM (RP) to create a si-VMAT model. Ten patients, with 2 to 6 metastases (mets), were planned with a si-VMAT technique utilising RP, and a mi-SRS technique on Brainlab iPlan. Paddick Conformity Index (PCI) was used to compare conformity. The volumes of the brain receiving 15Gy, 12Gy, 10Gy, 7.5Gy and 3Gy were also compared. Retrospective treatment times from the last eight patients treated were averaged for pre-imaging and beam on time to calculate treatment times for both techniques. Results: There was a significant difference in the PCI scores for the mi-SRS plans (M = 0.667, SD = 0.114) and si-VMAT plans (M = 0.728, SD = 0.088), with PCI values suggesting better prescription dose conformity with the si-VMAT technique (P = 0.014). Percentage of total brain volume receiving low-dose wash at four of the five different dose levels was significantly less (P < 0.05) with mi-SRS. Average time to treat a single met with current mi-SRS technique is 25.7 min, with each additional met requiring this same amount of time. The average time to treat 2-3 mets using si-VMAT would be 25.3 min and 4+ metastases 33.5 min. Conclusion: A knowledge-based si-VMAT approach was efficient in planning and treating multi metastases while achieving clinically acceptable dosimetry with respect to dose conformity and low-dose fall off.

Sparing the Hippocampus in Prophylactic Cranial Irradiation Using Three Different Linear Accelerators: A Comparative Study

“…Nevertheless, it is worth mentioning that a randomized phase III study by Belderbos et al (2019) did not find any difference in patients' memory compared to the standard PCI [17][18][19]. The VMAT technique for whole-cranial irradiation may protect the hippocampus by delivering a lower than the prescribed radiation dose to that organ in order to reduce toxicity, but with a higher number of MUs than a three-dimensional conformal radiation therapy (3DCRT) of whole-cranial and less than intensity-modulated radiation therapy (IMRT) [20,21]. Such a treatment plan is a challenge in clinical practice for the radiation therapy department since the thresholds for the hippocampus are pretty low and its volume is small compared to the volume of the whole brain.…”

Can the use of knowledge-based planning systems improve stereotactic radiotherapy planning? A systematic review

“…In contrast, in their multiple isocentre technique, each metastasis requires its own plan and treatment delivery. 40 Where quality improvements in studies are reported, it is not necessarily the case that KBP planning performs better in every metric. In some cases, improved performance in one area might be offset by a reduction in another.…”

“…For example, O'Toole et al found that the average CI were better in KBP plans but that low-dose wash was worse in four out of five dose levels. 40 Like all radiotherapy planning, there are trade-offs in what can be prioritised; therefore, studies that include blinded physician review are of particular interest, as discussed earlier.…”