Isotoxic dose escalation in the treatment of lung cancer by means of heterogeneous dose distributions in the presence of respiratory motion

Mariwan Baker, Morten Nielsen, Olfred Hansen, JW Jahn, Stine Korreman, Carsten Brink

    Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

    Abstract

    Purpose

    To test, in the presence of intrafractional respiration movement, a margin recipe valid for a homogeneous and conformal dose distribution and to test whether the use of smaller margins combined with heterogeneous dose distributions allows an isotoxic dose escalation when respiratory motion is considered.

    Methods and Materials

    Twenty-three Stage II–III non–small-cell lung cancer patients underwent four-dimensional computed tomography scanning. The gross tumor volume and clinical target volume (CTV) were outlined in the mid-ventilation phase. The CTV–to–planning target volume (PTV) margin was calculated by use of a standard margin recipe and the patient-specific respiration pattern. Standard three-dimensional treatment plans were generated and recalculated on the remaining respiration phases. The planning was repeated for a CTV-to-PTV margin decreased by 2.5 and 5 mm relative to the initial margin in all directions. Time-averaged dose–volume histograms (four-dimensional dose–volume histograms) were calculated to evaluate the CTV-to-PTV margin. Finally, the dose was escalated in the plans with decreased PTV such that the mean lung dose (predictor of radiation-induced pneumonitis) was equal to mean lung dose in the plan by use of the initially calculated margin.

    Results

    A reduction of the standard margin by 2.5 mm compared with the recipe resulted in too low of a minimum dose for some patients. A combination of dose escalation and use of heterogeneous dose distribution was able to increase the minimum dose to the target by approximately 10% and 20% for a CTV-to-PTV margin reduction of 2.5 mm and 5.0 mm, respectively.

    Conclusion

    The margin recipe is valid for intrafractional respiration-induced tumor motions. It is possible to increase the dose to the target without increased mean lung dose with an inhomogeneous dose distribution.
    OriginalsprogEngelsk
    TidsskriftInternational Journal of Radiation Oncology, Biology, Physics
    Vol/bind81
    Udgave nummer3
    Sider (fra-til)849-855
    ISSN0360-3016
    DOI
    StatusUdgivet - 1 nov. 2011

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