Three-dimensional dose evaluation in breast cancer patients to define decision criteria for adaptive radiotherapy

Catharina M L Zegers*, Jose A Baeza, Wouter van Elmpt, Lars H P Murrer, Karolien Verhoeven, Liesbeth Boersma, Frank Verhaegen, Sebastiaan M J J G Nijsten

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Background: Dose-guided adaptive radiation therapy (DGART) is the systematic evaluation and adaptation of the dose delivery during treatment for an individual patient. The aim of this study is to define quantitative action levels for DGART by evaluating changes in 3D dose metrics in breast cancer and correlate them with clinical expert evaluation.

Material and methods: Twenty-three breast cancer treatment plans were evaluated, that were clinically adapted based on institutional IGRT guidelines. Reasons for adaptation were variation in seroma, hematoma, edema, positioning or problems using voluntary deep inspiration breath hold. Sixteen patients received a uniform dose to the breast (clinical target volume 1; CTV1). Six patients were treated with a simultaneous integrated boost to CTV2. The original plan was copied to the CT during treatment (re-CT) or to the stitched cone-beam CT (CBCT). Clinical expert evaluation of the re-calculated dose distribution and extraction of dose-volume histogram (DVH) parameters were performed. The extreme scenarios were evaluated, assuming all treatment fractions were given to the original planning CT (pCT), re-CT or CBCT. Reported results are mean +/- SD.

Results: DVH results showed a mean dose (Dmean) difference between pCT and re-CT of -0.4 +/- 1.4% (CTV1) and -1.4 +/- 2.1% (CTV2). The difference in V95% was -2.6 +/- 4.4% (CTV1) and -9.8 +/- 8.3% (CTV2). Clinical evaluation and DVH evaluation resulted in a recommended adaptation in 17/23 or 16/23 plans, respectively. Applying thresholds on the DVH parameters: Dmean CTV, V95% CTV, Dmax, mean lung dose, volume exceeding 107% (uniform dose) or 90% (SIB) of the prescribed dose enabled the identification of patients with an assumed clinically relevant dose difference, with a sensitivity of 0.89 and specificity of 1.0. Re-calculation on CBCT imaging identified the same plans for adaptation as re-CT imaging.

Conclusions: Clinical expert evaluation can be related to quantitative DVH parameters on re-CT or CBCT imaging to select patients for DGART.

Original languageEnglish
Pages (from-to)1487-1494
Number of pages8
JournalActa Oncologica
Volume56
Issue number11
DOIs
Publication statusPublished - Nov 2017
Event15th Acta Oncologica Symposium - Biology-Guided Adaptive Radiotherapy (BiGART) - Aarhus, Denmark
Duration: 13 Jun 201716 Jun 2017

Keywords

  • Breast Neoplasms/radiotherapy
  • Cone-Beam Computed Tomography/methods
  • Decision Support Techniques
  • Female
  • Humans
  • Image Processing, Computer-Assisted/methods
  • Imaging, Three-Dimensional/methods
  • Organs at Risk/radiation effects
  • Radiotherapy Dosage
  • Radiotherapy Planning, Computer-Assisted/methods
  • Radiotherapy, Intensity-Modulated/methods
  • Retrospective Studies

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