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W. De Wever



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    MO23 - Radiotherapy II: Lung Toxicity, Target Definition and Quality Assurance (ID 107)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      MO23.10 - Addition of EBUS-mapping of the mediastinum to PET/CT based selective nodal irradiation in NSCLC decreases geographical miss and nodal GTV volume (ID 2841)

      11:25 - 11:30  |  Author(s): W. De Wever

      • Abstract
      • Presentation
      • Slides

      Background
      FDG-PET/CT based selective lymph node (LN) irradiation is the standard when using 3D-conformal techniques (3D-CRT) for locally advanced NSCLC. With 3D-CRT, adjacent LN not included in the target volume still receive a substantial radiation dose. With current new techniques (IMRT/VMAT), the radiation dose to non-involved LN decreases, which raises the question whether selective nodal irradiation based on PET/CT is still safe. We therefore evaluated the impact of adding EBUS-TBNA (endobronchial ultrasound guided transbronchial needle aspiration)-mapping of the mediastinal LN to PET/CT in avoiding geographical miss, and on the size of nodal GTV (gross tumor volume).

      Methods
      Consecutive NSCLC-patients referred for radiotherapy (RT) in 2012 who underwent EBUS-TBNA were included. False negative (FN) LN for different constellations of PET, CT and EBUS-TBNA based on literature data were calculated, to evaluate the safety of excluding LNs based on CT, PET and EBUS findings. A practical algorithm when to include LN in the GTV was made, and tested on our patients. Results are expressed as mean +/- SD and range.

      Results
      Twenty-five consecutive patients with a full EBUS-TBNA mapping before RT were included: 11 women, 14 men; 17 adenocarcinoma, 8 squamous cell carcinoma; 14 right-sided and 11 left-sided tumors. Mean age: 62.5 +/- 9.7 years. All patients had stage III-disease based on PET-CT. LN stations 1,2R,2L,3,4R,4L,5,6,7,8,9,10-11L,10-11R were analyzed on CT- and PET-scan (=325 LN). Sixty-seven were enlarged (≥10mm), of which 63 were PET-positive. Twelve normal-sized LNs were PET-positive. Fifty LNs were investigated with EBUS-TBNA (mean: 2/patient +/-0.96;1-5): 28 were malignant, 22 normal. EBUS-TBNA detected 1 cancer-containing normal-sized LN without FDG-uptake, thus 1/25 geographical miss (4%). The cancer prevalence, taking into account the FN rate of EBUS of 20%, was calculated (Fig.1). With addition of EBUS, in PET-negative patients FN decreases with 10% for enlarged LN, and with 5% for normal-sized LN. An algorithm when to include a LN in the GTV is proposed (Fig.1). According to this algorithm, in our population 3/79 (4%) enlarged or PET-positive LN would be excluded from the GTV. At patient level, this was a GTV decrease in 3 (12%) patients.

      Conclusion
      When incidental nodal irradiation is low such as in IMRT or VMAT, EBUS-TBNA should be added to FDG-PET/CT for mediastinal staging. This avoids geographical miss in 4% of patients, and decreases the radiation volume in 12% of patients. A practical algorithm is proposed.

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    P2.19 - Poster Session 2 - Imaging (ID 180)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Imaging, Staging & Screening
    • Presentations: 1
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      P2.19-004 - Characterization of solitary pulmonary lesions combining visual perfusion and quantitative diffusion MR imaging (ID 1000)

      09:30 - 09:30  |  Author(s): W. De Wever

      • Abstract

      Background
      To evaluate the diagnostic accuracy of dynamic contrast enhanced (DCE)magnetic resonance (MR) and diffusion weighted imaging (DWI) sequences for defining benign or malignant character of solitary pulmonary lesion (SPL) in a preoperative setting.

      Methods
      This study was approved by the local ethics committee; all patients provided written informed consent. First, 54 consecutive patients with SPL, clinically staged (CT and PET or integrated PET-CT) as N0M0, were included in this prospective study. An additional MR examination including DCE and DWI was performed one day before the surgical procedure. Histopathology of the surgical specimen served as standard of reference. Subsequently, this functional method for SPL characterization was validated with a second cohort of 54 patients.

      Results
      In the feasibility group, 11 benign and 43 malignant SPL were included with a maximal diameter that varied from 3 to 71 mm (mean 23.2 mm). Using the conventional MR sequences with visual interpretation of DCE-MR curves sensitivity, specificity, accuracy were respectively 100%, 55% and 91%. By additional interpretation of quantitative apparent diffusion coefficient (ADC) values (with a cutoff value of 1.52x10-3 mm2/sec for ADC calculated from high b-values (ADChigh) these results improved to 98%, 82% and 94% respectively. In the validation group, with 14 benign and 40 malignant SPL (diameter ranged between 7 mm and 10 cm - mean 26.5 mm), these results were confirmed with a sensitivity, specificity and accuracy of 95%, 79%, and 91%, respectively.

      Conclusion
      Visual DCE-MR-based curve interpretation can be used for initial differentiation of benign from malignant SPL, while additional quantitative DWI-based interpretation can further improve the specificity.