Effect of Photon-Beam Energy on VMAT and IMRT Treatment Plan Quality and Dosimetric Accuracy for Advanced Prostate Cancer

Der Einfluss der Photonenenergie auf VMAT- und IMRT-Planqualität und dosimetrische Genauigkeit für fortgeschrittenen Prostatatumor

Abstract

Purpose:

The goal of the research was to evaluate treatment plan quality and dosimetric accuracy of volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) plans using 6, 10, and 15 MV photon beams for prostate cancer including lymph nodes.

Methods:

In this retrospective study, VMAT and IMRT plans were generated with the Pinnacle© treatment planning system (TPS) (V9.0) for 10 prostate cancer cases. Each plan consisted of two target volumes: PTVB included the prostate bed, PTVPC+LN contained PTVB and lymph nodes. For plan evaluation statistics, the homogeneity index, conformity index, mean doses, and near-max doses to organs at risk (OAR) were analyzed. Treatment time and number of monitor units were assessed to compare delivery efficiency. Dosimetric plan verification was performed with a 2D ionization chamber array placed in a full scatter phantom.

Results:

No differences were found for target and OAR parameters in low and high energy photon beam plans for both VMAT and IMRT. A slightly higher low dose volume was detected for 6 MV VMAT plans (normal tissue: Dmean = 16.47 Gy) compared to 10 and 15 MV VMAT plans (Dmean = 15.90 Gy and 15.74 Gy, respectively), similar to the findings in IMRT. In VMAT, > 96% of detector points passed the 3%/ 3 mm γ criterion; marginally better accuracy was found in IMRT (> 97%).

Conclusion:

For static and rotational IMRT, 15 MV photons did not show advantages over 6 and 10 MV high energy photon beams in large volume pelvic plans. For the investigated TPS and linac combination, 10 MV photon beams can be used as the general purpose energy for intensity modulation.

Zusammenfassung

Ziel:

Vergleich von Planqualität und dosimetrischer Genauigkeit von volumetrisch modulierter Rotationstherapie (VMAT) und intensitätsmodulierter Strahlentherapie (IMRT) mit 6, 10 und 15 MV Photonenenergie für Patienten mit fortgeschrittenem Prostatatumor einschließlich Lymphabfluss.

Patienten und Methoden:

In dieser retrospektiven Planungsstudie wurden VMAT- und IMRT-Pläne mit dem Pinnacle©-Planungssystem (V9.0) für 10 Patienten mit Prostatatumoren (PC) generiert. Jeder Plan enthielt 2 Zielvolumina: PTVB umschloss die Prostata, PTVPC+LN beinhaltete PTVB und den Lymphabfluss. Für die Beurteilung der Planqualität wurden Homogenitätsindex, Konformitätsindex, mittlere Dosis und Nahe-Maximum-Dosis für Risikoorgane (OAR) berechnet. Als Parameter für die Bestrahlungseffizienz wurden Bestrahlungszeit und Anzahl der Monitoreinheiten (MU) herangezogen. Die Planverifikation wurde mit einer 2D Ionisationskammer-Matrix in einem Festkörperphantom durchgeführt.

Ergebnisse:

Es wurden keine Unterschiede zwischen niedrigen und hohen Energien für Zielvolumen- und Risikoorgan-Parametern in VMAT- und IMRT-Plänen gefunden (Tabellen 2 und 3, Abbildung 2). In 6-MV-VMAT-Plänen wurde ein geringfügig höheres Niedrigdosisvolumen (Normalgewebe: Dmean = 16,47 Gy) als in 10- und 15-MV-Plänen (je Dmean = 15,90 Gy und 15,74 Gy) gefunden; ähnliche Ergebnisse wurden für IMRT-Pläne ermittelt. VMAT-Pläne erreichten einen Gamma-Index < 1 (3 mm Abstand und 3% Dosis) für > 96% der Detektorpunkte; IMRT-Pläne erreichten > 97% der Detektorpunkte (Abbildung 3).

Schlussfolgerung:

Unsere Studie zeigt für große Beckenvolumina bei 15-MV-VMAT- und -IMRT-Plänen keinen Vorteil gegenüber Plänen mit 6 und 10 MV. Für die verwendete Kombination von TPS und Linac wurde festgestellt, dass 10-MV-Photonen als ‚Universal’-Energie für Intensitätsmodulation verwendet werden können.

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References

  1. 1.

    Alvarez-Moret J, Koelbl O, Bogner L. Quasi-IMAT technique and secondary cancer risk in prostate cancer. Strahlenther Onkol 2009;185:248–253.

    PubMed  Article  Google Scholar 

  2. 2.

    Bertelsen A, Hansen CR, Johansen J et al. Single arc volumetric modulated arc therapy of head and neck cancer. Radiother Oncol 2010;95:142–148.

    PubMed  Article  Google Scholar 

  3. 3.

    Boehmer D, Maingon P, Poortmans P et al. Guidelines for primary radiotherapy of patients with prostate cancer. Radiother Oncol 2006;79:259–269.

    PubMed  Article  Google Scholar 

  4. 4.

    Bzdusek K, Friberger H, Eriksson K et al. Development and evaluation of an efficient approach to volumetric arc therapy planning. Med Phys 2009;36:2328–2339.

    PubMed  Article  Google Scholar 

  5. 5.

    Clivio A, Fogliata A, Franzetti-Pellanda A et al. Volumetric-modulated arc radiotherapy for carcinomas of the anal canal: a treatment planning comparison with fixed field IMRT. Radiother Oncol 2009;92:118–124.

    PubMed  Article  Google Scholar 

  6. 6.

    Cotrutz C, Xing L. Segment-based dose optimisation using a genetic algorithm. Phys Med Biol 2003;48:2987–2998.

    PubMed  Article  Google Scholar 

  7. 7.

    Cozzi L, Dinshaw KA, Shrivastava SK et al. A treatment planning study comparing volumetric arc modulation with RapidArc and fixed field IMRT for cervix uteri radiotherapy. Radiother Oncol 2008;89:180–191.

    PubMed  Article  Google Scholar 

  8. 8.

    Eppinga E, Lagerwaard F, Verbakel W et al. Volumetric modulated arc therapy for advanced pancreatic cancer. Strahlenther Onkol 2010;186:382–387.

    PubMed  Article  Google Scholar 

  9. 9.

    Georg D, Stock M, Kroupa B et al. Patient-specific IMRT verification using independent fluence-based dose calculation software: experimental benchmarking and initial clinical experience. Phys Med Biol 2007;52(16):4981–4992.

    PubMed  Article  Google Scholar 

  10. 10.

    Georg D, Nyholm T, Olofsson J et al. Clinical evaluation of monitor unit software and the application of action levels. Radiother Oncol 2007;85:306–315.

    PubMed  Article  Google Scholar 

  11. 11.

    Hall EJ, Wuu CS. Radiation-induced second cancers: the impact of 3D-CRT and IMRT. Int J Radiat Oncol Biol Phys 2003;56:83–88.

    PubMed  Article  Google Scholar 

  12. 12.

    Hall EJ. Intensity-modulated radiation therapy, protons, and the risk of second cancers. Int J Radiat Oncol Biol Phys 2006;65:1–7.

    PubMed  Article  Google Scholar 

  13. 13.

    International Commission on Radiation Units and Measurements (ICRU). ICRU Report No. 83: Prescribing, Recording, and Reporting Photon-Beam Intensity-Modulated Radiation Therapy (IMRT).

  14. 14.

    Kry SF, Salehpour M, Titt U et al. Out-of-field photon and neutron dose equivalents from step-and-shoot intensitymodulated radiation therapy. Int J Radiat Oncol Biol Phys 2005;62:1204–1216.

    PubMed  Article  Google Scholar 

  15. 15.

    Laughlin JS, Mohan R, Kutcher GJ. Choice of optimum megavoltage for accelerators for photon beam treatment. Int J Radiat Oncol Biol Phys 1986;12:1551–1557.

    PubMed  Article  CAS  Google Scholar 

  16. 16.

    Lawton CA, Michalski J, El-Naqa I et al. RTOG GU Radiation oncology specialists reach consensus on pelvic lymph node volumens for high risk prostate cancer. Int J Radiat Oncol Biol Phys 2009;74:383–387.

    PubMed  Article  Google Scholar 

  17. 17.

    Low DA, Harms WB, Mutic S et al. A technique for the quantitative evaluation of dose distributions. Med Phys 1998;25:656–661.

    PubMed  Article  CAS  Google Scholar 

  18. 18.

    Matuszak M, Yan D, Grills I et al. Clinical applications of volumetric modulated arc therapy. Int J Radiat Oncol Biol Phys 2010;77:608–616.

    PubMed  Article  Google Scholar 

  19. 19.

    Michalski JM, Lawton, El-Naqa I et al. Development of RTOG consensus guidelines for the definition of the clinical target volume for postoperative conformal radiation therapy for prostate cancer. Int J Radiat Oncol Biol Phys 2010;76:361–368.

    PubMed  Article  Google Scholar 

  20. 20.

    Ost P, Speleers B, De Merleer G et al. Volumetric modulated arc therapy and intensity modulated radiotherapy for primary prostate radiotherapy with simultaneous integrated boost to intraprostatic lesion with 6 and 18 MV: a planning comparison study. Int J Radiat Oncol Biol Phys 2011;79:920–926.

    PubMed  Article  Google Scholar 

  21. 21.

    Paddick I. A simple scoring ratio to index the conformity of radiosurgical treatment plans. Technical note. J Neurosurg 2000;93:219–222.

    PubMed  Google Scholar 

  22. 22.

    Pirzkall A, Carol M, Pickett B et al. The effect of beam energy and number of fields on photon-based IMRT for deep-seated targets. Int J Radiat Oncol Biol Phys 2002;53:434–442.

    PubMed  Article  Google Scholar 

  23. 23.

    Ruben JD, Davis S, Evans C et al. The effect of intensity- modulated radiotherapy on radiation-induced second malignan- cies. Int J Radiat Oncol Biol Phys 2008;70:1530–1536.

    PubMed  Article  Google Scholar 

  24. 24.

    Schneider U, Lomax A, Pemler P et al. The impact of IMRT and proton radiotherapy on secondary cancer incidence. Strahlenther Onkol 2006;182:647–652.

    PubMed  Article  Google Scholar 

  25. 25.

    Shepard DM, Earl MA, Li XA et al. Direct aperture optimisation: a turnkey solution for step-and-shoot IMRT. Med Phys 2002;29:1007–1018.

    PubMed  Article  CAS  Google Scholar 

  26. 26.

    Sternick ES, Bleier AR, Carol MP et al. Intensity modulated radiation therapy: what photon energy is best? (Abstr.). Proceedings of the International Conference on the Use of Computers in Radiation Therapy (ICCR), XIIth Annual Meeting, Salt Lake City, UT. Madison, WI: Medical Physics Publishing; 1997; 418–419.

    Google Scholar 

  27. 27.

    Vandecasteele K, De Neve W, De Gersem W et al. Intensity-modulated arc therapy with simultaneous integrated boost in the treatment of primary irresectable cervical cancer. Strahlenther Onkol 2009;185:799–807.

    PubMed  Article  Google Scholar 

  28. 28.

    Vanetti E, Clivio A, Nicolini G et al. Volumetric modulated arc radiotherapy for carcinomas of the oro-pharynx, hypo-pharynx and larynx: A treatment planning comparison with fixed field IMRT. Radiother Oncol 2009;92:111–117.

    PubMed  Article  Google Scholar 

  29. 29.

    Van Esch A, Clermont C, Devillers M et al. On-line quality assurance of rotational radiotherapy treatment delivery by means of a 2D ion chamber array and the Octavius phantom. Med Phys 2007;34:3825–3837.

    PubMed  Article  Google Scholar 

  30. 30.

    Wiezorek T, Banz N, Schwedas M et al. Dosimetric quality assurance for intensity- modulated radiotherapy. Feasibility study for a filmless approach. Strahlenther Onkol 2005;181:468–474.

    PubMed  Article  Google Scholar 

  31. 31.

    Wiezorek T, Voigt A, Metzger N et al. Experimental determination of peripheral doses for different IMRT techniques delivered by a Siemens linear accelerator. Strahlenth Onkol 2008;184:73–79.

    Article  Google Scholar 

  32. 32.

    Wolff D, Stieler F, Hermann B et al. Clinical Implementation of Volumetric Intensity-modulated arc therapy (VMAT) with ERGO++. Strahlenther Onkol 2010;186:280–288.

    PubMed  Article  Google Scholar 

  33. 33.

    Yu CX. Intensity-modulated arc therapy with dynamic multileaf collimation: an alternative to tomotherapy. Phys Med Biol 1995;40:1435–1449.

    PubMed  Article  CAS  Google Scholar 

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Correspondence to Assoc. Prof. Dr. Dietmar Georg.

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Pasler, M., Georg, D., Wirtz, H. et al. Effect of Photon-Beam Energy on VMAT and IMRT Treatment Plan Quality and Dosimetric Accuracy for Advanced Prostate Cancer. Strahlenther Onkol 187, 792–798 (2011). https://doi.org/10.1007/s00066-011-1150-0

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Key Words

  • VMAT
  • IMRT
  • Advanced prostate cancer

Schlüsselwörter

  • VMAT
  • IMRT
  • Fortgeschrittener Prostatatumor