Abstract
Background
The dosimetric variability in spine stereotactic body radiation therapy (SBRT) planning was investigated in a large number of centres to identify crowd knowledge-based solutions.
Methods
Two spinal cases were planned by 48 planners (38 centres). The required prescription dose (PD) was 3 × 10 Gy and the planning target volume (PTV) coverage request was: VPD > 90% (minimum request: VPD > 80%). The dose constraints were: planning risk volume (PRV) spinal cord: V18Gy < 0.35 cm3, V21.9 Gy < 0.03 cm3; oesophagus: V17.7 Gy < 5 cm3, V25.2 Gy < 0.03 cm3. Planners who did not fulfil the protocol requirements were asked to re-optimize the plans, using the results of planners with the same technology. Statistical analysis was performed to assess correlations between dosimetric results and planning parameters. A quality index (QI) was defined for scoring plans.
Results
In all, 12.5% of plans did not meet the protocol requirements. After re-optimization, 98% of plans fulfilled the constraints, showing the positive impact of knowledge sharing. Statistical analysis showed a significant correlation (p < 0.05) between the homogeneity index (HI) and PTV coverage for both cases, while the correlation between HI and spinal cord sparing was significant only for the single dorsal PTV case. Moreover, the multileaf collimator leaf thickness correlated with the spinal cord sparing. Planners using comparable delivery/planning system techniques produced different QI, highlighting the impact of the planner’s skills in the optimization process.
Conclusion
Both the technology and the planner’s skills are fundamentally important in spine SBRT planning optimization. Knowledge sharing helped to follow the plan objectives.
Zusammenfassung
Hintergrund
Die dosimetrische Variabilität in der Bestrahlungsplanung der spinalen stereotaktischen Körperstamm-Strahlentherapie (SBRT) wurde in einer großen Anzahl von Kliniken untersucht, um eine Gruppenwissen-abhängige Lösung zu finden.
Methoden
Zwei spinale Behandlungsfälle wurden von 48 Planern (38 Kliniken) geplant. Die geforderte verschriebene Dosis (VD) lag bei 3 × 10 Gy, und die zu erreichende PTV-Abdeckung bei VVD > 90 % (minimale Anforderung: VVD > 80 %). Die Dosislimitierungen waren: „PRV spinal cord“: V18Gy < 0,35 cm3, V21.9 Gy < 0,03 cm3; „oesophagus“: V17.7 Gy < 5 cm3, V25.2 Gy < 0,03 cm3. Planer, die die Protokollanforderungen nicht erfüllten, wurden gebeten, die Pläne unter Verwendung der Ergebnisse von Planern mit der gleichen Technologie erneut zu optimieren. Eine statistische Analyse wurde durchgeführt, um die Korrelation zwischen dosimetrischen Ergebnissen und Planungsparametern zu untersuchen. Ein Qualitätsindex (QI) wurde festgelegt, um das Abschneiden der Pläne zu bestimmen.
Ergebnisse
Insgesamt 12,5 % der Pläne haben die Protokollanforderungen nicht erfüllt. Nach Reoptimierung erfüllten 98 % der Pläne die Bedingungen, was den positiven Einfluss des Wissensaustauschs zeigte. Die statistische Analyse zeigte in beiden Fällen eine signifikante Korrelation (p < 0,05) zwischen Homogenitätsindex (HI) und PTV-Abdeckung, während die Korrelation zwischen HI und Rückenmarkschonung nur für den einzelnen dorsalen PTV-Fall signifikant war. Darüber hinaus korrelierte die MLC-Blattdicke mit der Schonung des Rückenmarks. Planer, die vergleichbare Bestrahlungs‑/Planungssystem-Techniken nutzen, produzierten unterschiedliche QI, was den Einfluss der Erfahrungen des Planers im Optimierungsprozess verdeutlichte.
Schlussfolgerung
Sowohl die Technologie als auch die Erfahrungen des Planers sind für die Optimierung der spinalen SBRT-Planung äußerst wichtig. Der Wissensaustausch half dabei, die Planungsbedingungen erfüllen zu können.
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Acknowledgements
The authors thank Miss Verlie Jones, dosimetrist at the European Institute of Oncology, for her editorial assistance in English.
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M. Esposito, L. Masi, M. Zani, R. Doro, D. Fedele, C. Garibaldi, S. Clemente, C. Fiandra, F.R. Giglioli, C. Marino, L. Orsingher, S. Russo, M. Stasi, L. Strigari, E. Villaggi and P. Mancosu declare that they have no competing interests.
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Esposito, M., Masi, L., Zani, M. et al. SBRT planning for spinal metastasis: indications from a large multicentric study. Strahlenther Onkol 195, 226–235 (2019). https://doi.org/10.1007/s00066-018-1383-2
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DOI: https://doi.org/10.1007/s00066-018-1383-2
Keywords
- Crowd knowledge-based optimization
- Stereotactic body radiation therapy
- Radiotherapy
- Spine metastasis
- Treatment planning