Abstract
BackgroundWe retrospectively evaluated the efficacy and toxicity of gross tumor volume (GTV) mean-dose-optimized and real-time motion-compensated robotic stereotactic body radiation therapy (SBRT) in the treatment of liver metastases.MethodsBetween March 2011 and July 2015, 52 patients were treated with SBRT for a total of 91 liver metastases (one to four metastases per patient) with a median GTV volume of 12 cc (min 1 cc, max 372 cc). The optimization of mean GTV dose was prioritized during treatment planning at the potential cost of planning target volume (PTV) coverage reduction while adhering to safe normal tissue constraints. The delivered median GTV biological effective dose (BED10) was 142.1 Gy10 (range, 60.2 Gy10 –165.3 Gy10) and the prescribed PTV BED10 ranged from 40.6 Gy10 to 112.5 Gy10 (median, 86.1 Gy10). We analyzed local control (LC), progression-free interval (PFI), overall survival (OS), and toxicity.ResultsMedian follow-up was 17 months (range, 2–49 months). The 2-year actuarial LC, PFI, and OS rates were 82.1, 17.7, and 45.0 %, and the median PFI and OS were 9 and 23 months, respectively. In univariate analysis histology (p < 0.001), PTV prescription BED10 (HR 0.95, CI 0.91–0.98, p = 0.002) and GTV mean BED10 (HR 0.975, CI 0.954–0.996, p = 0.011) were predictive for LC. Multivariate analysis showed that only extrahepatic disease status at time of treatment was a significant factor (p = 0.033 and p = 0.009, respectively) for PFI and OS. Acute nausea or fatigue grade 1 was observed in 24.1 % of the patients and only 1 patient (1.9 %) had a side effect of grade ≥ 2.ConclusionsRobotic real-time motion-compensated SBRT is a safe and effective treatment for one to four liver metastases. Reducing the PTV prescription dose and keeping a high mean GTV dose allowed the reduction of toxicity while maintaining a high local control probability for the treated lesions.
Highlights
We retrospectively evaluated the efficacy and toxicity of gross tumor volume (GTV) mean-dose-optimized and real-time motion-compensated robotic stereotactic body radiation therapy (SBRT) in the treatment of liver metastases
Because of the large amount of inoperable patients and because hepatic recurrences occur in nearly two thirds of the patients after surgical resection [10], several alternative or complementary therapies have been established such as radiofrequency ablation (RFA) [11], trans-arterial chemoembolization (TACE) [12], laser-induced thermotherapy (LITT) [13], selective internal radiation therapy (SIRT) [14] or stereotactic body radiation therapy (SBRT) [15,16,17,18,19,20,21]
In univariate analysis histology, planning target volume (PTV) prescription BED10 (Hazard Ratio hazard ratio (HR) 0.95, 95 % confidence interval (CI) 0.91– 0.98, p = 0.002) and GTV mean BED10 (HR 0.975, CI 0.954–0.996, p = 0.011), both variables considered as continuous variables, were predictive for local control
Summary
We retrospectively evaluated the efficacy and toxicity of gross tumor volume (GTV) mean-dose-optimized and real-time motion-compensated robotic stereotactic body radiation therapy (SBRT) in the treatment of liver metastases. New developments in SBRT technology, such as active-breathing-controlled tumor localization [21] or real-time tumor-tracking technology (CyberKnife®, Accuray Incorporated, Sunnyvale, CA, USA) [22, 23], have allowed the application of high radiation doses within the gross tumor volume (GTV) while applying minimal safety margins aiming at maximal sparing of surrounding normal tissue. This is especially challenging in presence of large tumor motion which is predominantly found in the lower part of the lung and in the liver. A dose response relationship for local control of liver metastases has been reported and effective SBRT of liver metastases should aim at delivering high biologically effective radiation doses (BED) within the tumor [15, 17, 24]
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