Tumor-dose-rate variations during robotic radiosurgery of oligo and multiple brain metastases

• Published in: Strahlentherapie und Onkologie 2021-07, Vol.197 (7), p.581-591
• Main Authors: Wilhelm, Maria-Lisa, Chan, Mark K. H., Abel, Benedikt, Cremers, Florian, Siebert, Frank-Andre, Wurster, Stefan, Krug, David, Wolff, Robert, Dunst, Jürgen, Hildebrandt, Guido, Schweikard, Achim, Rades, Dirk, Ernst, Floris, Blanck, Oliver
• Format: Article
• Language: English
• Subjects: Brain; Brain cancer; Breast cancer; Collimators; Confidence intervals; Dosage; Histology; Lesions; Mathematical analysis; Medicine; Medicine & Public Health; Metastasis; Multivariate analysis; Oncology; Original; Original Article; Radiation effects; Radiology; Radiosurgery; Radiotherapy; Robotic surgery; Tumors
• ISSN: 0179-7158; 1439-099X
• DOI: 10.1007/s00066-020-01652-6

Purpose For step-and-shoot robotic stereotactic radiosurgery (SRS) the dose delivered over time, called local tumor-dose-rate (TDR), may strongly vary during treatment of multiple lesions. The authors sought to evaluate technical parameters influencing TDR and correlate TDR to clinical outcome. Material and methods A total of 23 patients with 162 oligo (1–3) and multiple (>3) brain metastases (OBM/MBM) treated in 33 SRS sessions were retrospectively analyzed. Median PTV were 0.11 cc (0.01–6.36 cc) and 0.50 cc (0.12–3.68 cc) for OBM and MBM, respectively. Prescription dose ranged from 16 to 20 Gy prescribed to the median 70% isodose line. The maximum dose-rate for planning target volume (PTV) percentage  p in time span  s during treatment (TDR s,p ) was calculated for various  p and  s based on treatment log files and in-house software. Results TDR 60min,98% was 0.30 Gy/min (0.23–0.87 Gy/min) for OBM and 0.22 Gy/min (0.12–0.63 Gy/min) for MBM, respectively, and increased by 0.03 Gy/min per prescribed Gy. TDR 60min,98% strongly correlated with treatment time (ρ = −0.717, p