MO-G-201-04: Knowledge-Based Planning for Single-Isocenter Stereotactic Radiosurgery to Multiple Brain Metastases

Abstract Background Single-isocenter dynamic conformal arc (SIDCA) therapy is an efficient way of delivering stereotactic radiosurgery (SRS) to multiple metastases simultaneously. This study reports on the safety and feasibility of SRS with SIDCA for patients with multiple brain metastases.Methods All patients who received SRS with this technique between November 2017 and June 2019 within a prospective registry trial, were included. The patients were irradiated using a VersaHD® linear accelerator (LINAC) from Elekta (Stockholm, Sweden). Follow-up was performed every three months, including a clinical and radiological examination with cranial magnetic resonance imaging (MRI). The data were analyzed using descriptive statistics and the Kaplan-Meier method.Results 65 patients with 254 lesions (range 2–12) were included in this analysis. Median beam on time was 23 minutes. The median follow-up at the time of analysis was 13 months (95% CI 11.1–14.9). Median overall survival and median progression-free survival was 15 months (95% CI 7.7–22.3) and 18 months (95% CI 11.1–24.9), respectively. Intracranial and local control after 6 months was 73.0% and 97.5%, respectively. During follow-up, CTCAE grade 1 adverse effects (AE) were experienced by 29 (44.6%) patients (18 of them therapy-related (27.7%)), CTCAE grade 2 AEs by 4 (6.2%) patients (one of them therapy-related (1.5%)) and CTCAE grade 3 by 3 patients (4.6%) (none of them therapy-related). 2 lesions (0.8%) in 2 patients (3.1%) were proven as radiation necrosis. Conclusions Simultaneous SRS using SIDCA seems to be a feasible and safe treatment for patients with multiple metastases.

Download Full-text

Operation and calibration of the novel PTW 1600SRS detector for the verification of single isocenter stereotactic radiosurgery treatments of multiple small brain metastases

British Journal of Radiology ◽

10.1259/bjr.20210473 ◽

2021 ◽

pp. 20210473

Author(s):

Esther Decabooter ◽

Ans CC Swinnen ◽

Michel C Öllers ◽

Fabian Göpfert ◽

Frank Verhaegen

Keyword(s):

Brain Metastases ◽

Stereotactic Radiosurgery ◽

Volumetric Modulated Arc Therapy ◽

Calibration Procedure ◽

Accurate Solution ◽

Array Detector ◽

Multiple Brain Metastases ◽

Flattening Filter Free ◽

Cross Calibration ◽

Single Isocenter

Objectives: The aim of this work was to evaluate the operation of the 1600SRS detector and to develop a calibration procedure for verifying the dose delivered by a single isocenter stereotactic radiosurgery (SRS) treatment of small multiple brain metastases (BM). Methods: 14 clinical treatment cases were selected with the number of BM ranging from 2 to 11. The dosimetric agreement was investigated between the calculated and the measured dose by an OCTAVIUS 1600SRS array detector in an OCTAVIUS 4D phantom equipped with dedicated SRS top. The cross-calibration procedure deviated from the manufacturer’s as it applied field sizes and dose rates corresponding to the volumetric modulated arc therapy segments in each plan. Results: Measurements with a plan specific cross-calibration showed mean ± standard deviation (SD) agreement scores for cut-off values 50%, 80%, 95%, of 98.6 ± 1.7%, 96.5 ± 4.6%, 97.3 ± 4.4% for the 6 MV plans respectively, and 98.6 ± 1.5%, 96.6 ± 4.0% 96.4 ± 6.3%, for the 6 MV flattening filter free (FFF) plans respectively. Using the default calibration procedure instead of the plan specific calibration could lead to a combined systematic dose offset of 4.1% for our treatment plans. Conclusion: The 1600SRS detector array with the 4D phantom offers an accurate solution to perform routine quality assurance measurements of single isocenter SRS treatments of multiple BM. This work points out the necessity of an adapted cross-calibration procedure. Advances in knowledge: A dedicated calibration procedure enables accurate dosimetry with the 1600SRS detector for small field single isocenter SRS treatment of multiple brain metastases for a large amount of BM.

Download Full-text