Strahlentherapie und Onkologie

, Volume 188, Issue 6, pp 484–491 | Cite as

Chest wall radiotherapy with volumetric modulated arcs and the potential role of flattening filter free photon beams

  • S. Subramaniam
  • S. Thirumalaiswamy
  • C. Srinivas
  • G.A. Gandhi
  • M. Kathirvel
  • K.K. Kumar
  • S. Mallik
  • M. Babaiah
  • Y. Pawar
  • A. Clivio
  • A. Fogliata
  • P. Mancosu
  • G. Nicolini
  • E. Vanetti
  • L. Cozzi
Original article

Abstract

Purpose

The goal of the work was to assess the role of RapidArc treatments in chest wall irradiation after mastectomy and determine the potential benefit of flattening filter free beams.

Methods and material

Planning CT scans of 10 women requiring post-mastectomy chest wall radiotherapy were included in the study. A dose of 50 Gy in 2 Gy fractions was prescribed. Organs at risk (OARs) delineated were heart, lungs, contralateral breast, and spinal cord. Dose–volume metrics were defined to quantify the quality of concurrent treatment plans assessing target coverage and sparing of OARs. Plans were designed for conformal 3D therapy (3DCRT) or for RapidArc with double partial arcs (RA). RapidArc plans were optimized for both conventional beams as well as for unflattened beams (RAF). The goal for this planning effort was to cover 100% of the planning target volume (PTV) with ≥ 90% of the prescribed dose and to minimize the volume inside the PTV receiving > 105% of the dose. The mean ipsilateral lung dose was required to be lower than 15 Gy and V20 Gy < 22%. Contralateral organ irradiation was required to be kept as low as possible.

Results

All techniques met planning objectives for PTV and for lung (3DCRT marginally failed for V20 Gy). RA plans showed superiority compared to 3DCRT in the medium to high dose region for the ipsilateral lung. Heart irradiation was minimized by RAF plans with ~4.5 Gy and ~15 Gy reduction in maximum dose compared to RA and 3DCRT, respectively. RAF resulted in superior plans compared to RA with respect to contralateral breast and lung with a reduction of ~1.7 Gy and 1.0 Gy in the respective mean doses.

Conclusion

RapidArc treatment resulted in acceptable plan quality with superior ipsilateral tissue sparing compared to traditional techniques. Flattening filter free beams, recently made available for clinical use, might provide further healthy tissue sparing, particularly in contralateral organs, suggesting their applicability for large and complex targets.

Keywords

Breast cancer Thoracic wall Radiotherapy RapidArc Flattening filter free photons 

Brustwandbestrahlung mittels volumetrisch modulierter Bögen und die potentielle Rolle von Photonenfeldern ohne Ausgleichsfilter

Zusammenfassung

Ziel

Bewertung von RapidArc-Behandlungen bei der Brustwandbestrahlung nach Mastektomie und die potentielle Rolle von Photonenfeldern ohne Ausgleichsfilter.

Material und Methoden

Die Planungs-CT-Bilder von 10 Frauen, die eine Brustwandbestrahlung nach Mastektomie benötigten, wurden in die Studie eingeschlossen. Es wurde eine Dosis von 50 Gy in 2-Gy-Fraktionen verschrieben. Folgede Risikorgane (RO) wurden berücksichtigt: Herz, Lungen, kontralaterale Brust und Rückenmark. Es wurden Dosis-Volumen-Maße festgelegt, um die Qualität von anderen Therapieplänen hinsichtlich Zielvolumenabdeckung und Schonung von RO zu quantifizieren. Die Pläne wurden für die konformale 3-D-Therapie (3DCRT) oder für RapidArc mit 2 partiellen Bögen (RA) errechnet. Die RapidArc-Pläne wurden sowohl für konventionelle Felder als auch für Felder ohne Ausgleichsfilter (RAF) optimiert. Das Ziel dieser Pläne war, 100% des PTV mit ≥ 90% der verschriebenen Dosis abzudecken und innerhalb des PTV das Volumen, auf das > 105% der Dosis trifft, zu minimieren. Die mittlere Dosis der ipsilateralen Lunge sollte < 15 Gy und V20 Gy < 22% sein. Die Dosis in den kontralateralen Organen war so niedrig wie möglich zu halten.

Ergebnisse

Alle Techniken erreichten die Planungsziele für PTV und Lunge (3DCRT verfehlte es knapp für V20 Gy). RA-Pläne zeigten sich im Vergleich zu 3DCRT im mittleren bis hohen Dosisbereich für die ipsilaterale Lunge überlegen. Die Dosisbelastung des Herzens wurde durch RAF-Pläne mit einer Rücknahme von ~4,5 Gy und ~15 Gy der maximalen Dosis im Vergleich zu RA oder 3DCRT minimiert. Verglichen mit den RA-Plänen ergaben die RAF-Pläne eine Verringerung der mittleren Dosis der kontralateralen Brust und Lunge um ~1,7 Gy bzw. 1,0 Gy.

Schlussfolgerung

Die RapidArc-Technik führte im Vergleich mit herkömmlichen Techniken zu einer akzeptablen Planungsqualität mit erhöhter Schonung von ipsilateralem Gewebe. Die vor kurzem in die klinische Praxis eingeführten Photonenfelder ohne Ausgleichsfilter könnten die Schonung des gesunden Gewebes weiter verbessern, insbesondere in den kontralateralen Organen, was für eine Anwendbarkeit bei großen und komplexen Zielevolumina spricht.

Schlüsselwörter

Brustkrebs Brustwand Strahlentherapie RapidArc Photonenfelder ohne Ausgleichsfilter 

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Copyright information

© Urban & Vogel 2012

Authors and Affiliations

  • S. Subramaniam
    • 1
  • S. Thirumalaiswamy
    • 1
  • C. Srinivas
    • 1
  • G.A. Gandhi
    • 1
  • M. Kathirvel
    • 1
  • K.K. Kumar
    • 1
  • S. Mallik
    • 1
  • M. Babaiah
    • 1
  • Y. Pawar
    • 1
  • A. Clivio
    • 2
  • A. Fogliata
    • 2
  • P. Mancosu
    • 3
  • G. Nicolini
    • 2
  • E. Vanetti
    • 2
  • L. Cozzi
    • 2
  1. 1.Yashoda Super Speciality HospitalHyderabadIndia
  2. 2.Medical Physics, Oncology Institute of Southern SwitzerlandOsp.S.GiovanniBellinzonaSwitzerland
  3. 3.Radiation Oncology DepartmentIstituto Clinico HumanitasMilan-RozzanoItaly

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