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Introduction
We retrospectively evaluated the efficacy and toxicity of gross tumor volume (GTV) mean dose optimized stereotactic body radiation therapy (SBRT) for primary and secondary lung tumors with and without robotic real-time motion compensation.
Materials and methods
Between 2011 and 2017, 208 patients were treated with SBRT for 111 primary lung tumors and 163 lung metastases with a median GTV of 8.2 cc (0.3–174.0 cc). Monte Carlo dose optimization was performed prioritizing GTV mean dose at the potential cost of planning target volume (PTV) coverage reduction while adhering to safe normal tissue constraints. The median GTV mean biological effective dose (BED)10 was 162.0 Gy10 (34.2–253.6 Gy10) and the prescribed PTV BED10 ranged 23.6–151.2 Gy10 (median, 100.8 Gy10). Motion compensation was realized through direct tracking (44.9%), fiducial tracking (4.4%), and internal target volume (ITV) concepts with small (≤5 mm, 33.2%) or large (>5 mm, 17.5%) motion. The local control (LC), progression-free survival (PFS), overall survival (OS), and toxicity were analyzed.
Results
Median follow-up was 14.5 months (1–72 months). The 2-year actuarial LC, PFS, and OS rates were 93.1, 43.2, and 62.4%, and the median PFS and OS were 18.0 and 39.8 months, respectively. In univariate analysis, prior local irradiation (hazard ratio (HR) 0.18, confidence interval (CI) 0.05–0.63, p = 0.01), GTV/PTV (HR 1.01–1.02, CI 1.01–1.04, p < 0.02), and PTV prescription, mean GTV, and maximum plan BED10 (HR 0.97–0.99, CI 0.96–0.99, p < 0.01) were predictive for LC while the tracking method was not (p = 0.97). For PFS and OS, multivariate analysis showed Karnofsky Index (p < 0.01) and tumor stage (p ≤ 0.02) to be significant factors for outcome prediction. Late radiation pneumonitis or chronic rip fractures grade 1–2 were observed in 5.3% of the patients. Grade ≥3 side effects did not occur.
Conclusion
Robotic SBRT is a safe and effective treatment for lung tumors. Reducing the PTV prescription and keeping high GTV mean doses allowed the reduction of toxicity while maintaining high local tumor control. The use of real-time motion compensation is strongly advised, however, well-performed ITV motion compensation may be used alternatively when direct tracking is not feasible.
1751 histologische Befunde des Zeitraumes 1990-1995 werden mit 1711 des Zeitraumes 1982-1987 verglichen. 1990-1995 wurden 573 Mammakarzinome neu diagnostiziert (1982-1987 n=499). Als Maß für die Effektivität der Diagnostik werden die Tumorgröße und der axillare Lymphknotenbefall zum Zeitpunkt der Erstdiagnose angesehen. Das Verhältnis von benignen zu malignen Veränderungen beträgt in Stralsund in beiden Zeiträumen 2:1, in Bergen (Rügen) hat es sich von 5:1 auf 2:1 verbessert. 1990-1995 Nachweis einer signifikanten Verschiebung zu niedrigeren Tumorstadien (50,1%<=pT1). Andererseits hat die Zahl der Patientinnen mit einem Tumor >50 mm signifikant zugenommen. Die Häufigkeit der Patientinnen mit axillaren Lymphknotenmetastasen hat sich nicht signifikant verändert. Die Zahl der entnommenen Lymphknoten pro Axilladissektion hat im Zeitraum 1990-1995 zugenommen. Die Ergebnisse werden als Maß für die Effizienz der in Deutschland zur Verfügung stehenden Früherkennungsmaßnahmen angesehen.