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W. Vogel



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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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      MO23.07 - Impact of a gradient-based FDG-PET auto-contouring method on non-small cell lung cancer delineation (ID 1993)

      11:10 - 11:15  |  Author(s): W. Vogel

      • Abstract
      • Presentation
      • Slides

      Background
      Manual target volume delineation using CT/FDG-PET is the standard method used for radiotherapy treatment planning of non-small cell lung cancer (NSCLC) patients. Since manual delineation is prone to inter-observer variability and is time consuming, many FDG-PET auto-contouring methods were proposed in literature. The purpose of this study was to investigate to what extent a gradient-based FDG-PET auto-contouring method reduces observer variation, reduces delineation time and influences delineation behavior in radiotherapy treatment planning for NSCLC patients.

      Methods
      Seven radiation oncologists (observers) dedicated to lung cancer treatment delineated the primary tumor (PT) and involved lymph nodes (LN) for 10 patients with stage IIA-IIIB NSCLC on a co-registered CT/FDG-PET scan. The study was separated in two phases. In the first phase, the observers manually delineated the PT and LN for all patients. For the second phase (four months later), auto-contours were generated for both the PT and LN using a gradient-based FDG-PET segmentation method. Bone and air tissue were removed from these auto-contours using CT thresholding. These auto-contours were provided as initial delineation and were adapted by the observers. Delineation times, delineated contours and agreement with the auto-contour were analyzed. Delineated contours were analyzed based on volume, the ratio between the common volume and the encompassing volume (C/E), Dice Index (DI), local standard deviation (SD) and the local distance between median surface and delineated surface. Regions were identified where the observers did or did not change the provided auto-contours.

      Results
      The observers agreed with the provided auto-contour for 37.3% of the PT and for 42.6% of the LN. Notable regions of agreement were the tumor/bone and tumor/air interfaces. The mean delineation time was reduced by 23.9% from 25.5 minutes in phase 1 to 19.4 minutes for phase 2 (p=0.000). The mean delineated volume was smaller in phase 2 compared to phase 1: 8.9% for the PT (155.8 to 142.0 cm[3], p=0.000) and by 9.1% for the LN (13.2 to 12.0 cm[3], p=0.001), respectively. The C/E ratio and DI both did not change significantly and were 0.79 and 0.88 for the PT and 0.54 and 0.67 for the LN in both phases. The mean local SD for the PT was 1.7 mm and 1.5 mm and for the LN was 1.5 mm and 1.4 mm and both did not change significantly, for both phases respectively. The mean distance between the median surface and PT delineations was slightly reduced from 2.1 to 1.8 mm for phase 2, and was 2.0 mm for the LN in both phases.

      Conclusion
      The gradient-based FDG-PET auto-contouring method reduced delineation time by 24%, but was sufficient in only 37.3% of the primary tumors and 42.6% of the involved lymph nodes; most notably at the tumor/bone and tumor/air interfaces segmented using the CT scan. The results suggest the FDG-PET auto-contour is currently primarily used for localization, and not so much for delineation. Multi-modal auto-contouring has the potential to reduce inter-observer variation when further developed in close collaboration with radiation oncologists.

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    P3.08 - Poster Session 3 - Radiotherapy (ID 199)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      P3.08-014 - Very high radiation dose escalation in NSCLC does not lead to unexpected toxicity: A planned toxicity analysis of the PET-boost study (NCT01024829) (ID 1925)

      09:30 - 09:30  |  Author(s): W. Vogel

      • Abstract

      Background
      Locoregional failure rates are high in patients with locally advanced non-small cell lung cancer (NSCLC), even when using concurrent chemoradiation. Recurrences have been shown to be predominantly located in the primary tumor, more specifically in areas with a high FDG-uptake that can be identified on a pre-treatment FDG PET-CT scan. Improved tumor control could be accomplished by dose escalation. The PET-boost trial is an ongoing randomized phase II trial investigating radiation dose-escalation using an individualized, accelerated schedule either to the entire primary tumor or to the regions of high FGD-uptake (>50% SUVmax) within the primary tumor. We present a preliminary analysis of the acute toxicity of the first 45 patients.

      Methods
      Patients with NSCLC stage IB-III with a primary tumor diameter ≥4 cm are eligible. Patients are treated with concurrent or sequential chemoradiation or radiotherapy only. Permitted regimens are: daily dose cisplatin (only in concurrent chemoradiation) or cisplatin-etoposide in concurrent and sequential chemoradiation. Eligible patients receive a planning PET-CT scan on which an IMRT plan is constructed up to a dose of 66 Gy in 24 fractions of 2.75 Gy to the involved lymph nodes and the primary tumor. In patients where normal tissue constraints allow further dose escalation to the primary tumor up to a minimal dose of 72 Gy of ≥ 3 Gy-fractions, 2 plans (with equal mean lung dose) are constructed: either giving the integrated boost to the entire primary tumor (Arm A) or redistributing the boost to areas of high FGD-uptake (>50% SUVmax) in the tumor (Arm B), up to a maximal prescribed dose of 129.6 Gy in 24 fractions of 5.4 Gy. All pts are followed according to study protocol. Toxicity is scored according to the CTCv3.0 criteria. Primary endpoint of this study is local progression-free survival at 1 year. Secondary endpoints are acute and late toxicity, overall survival and quality of life.

      Results
      Between 2010 and 2013 71 patients were registered of which 45 were randomized: 22 pts to arm A and 23 to arm B. In both arms, median follow up was 13.3 months. Patient and tumor characteristics were equally distributed in both arms. Thirty-seven patients (82.2%) had stage III lung cancer. Concurrent chemoradiotherapy was given in 25 patients (55.6%). Mean GTV was 154.2 cm ³ (range 26-416 cm³). Mean fraction size in both arms was 3.46 Gy (range 3.0-5.4 Gy). Baseline toxicity grade 3 occurred in 4 patients (8.8%) consisting of dyspnea in 1 patient, cough in 2 patients and renal dysfunction in 1 patient. During treatment grade ≥3 hematologic toxicity was seen in 6 patients (13.3%), whereas 2 patients (4.4%) suffered from cardiac toxicity grade 4 (ischemia/infarction). Seven patients (15.6%) had grade ≥3 dysphagia. 82.2% of the patients finished treatment according to study protocol. Radiation treatment was completed in all patients. Seven patients have died of which 3 (6.6%) due to pulmonary hemorrhage.

      Conclusion
      This first toxicity analysis of the multicenter phase II randomized PET-boost trial at a median follow up of 13.3 months did not reveal any unexpected acute or late toxicity.