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A. Van Baardwijk



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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): A. Van Baardwijk

      • 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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    O27 - Clinical Trials and Practice (ID 142)

    • Event: WCLC 2013
    • Type: Oral Abstract Session
    • Track: Other Topics
    • Presentations: 1
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      O27.05 - Is primary tumor standardized uptake value (SUV) an independent prognostic factor for non-small cell lung cancer (NSCLC)? A meta-analysis based on individual patients data. (ID 3888)

      17:00 - 17:10  |  Author(s): A. Van Baardwijk

      • Abstract
      • Presentation
      • Slides

      Background
      [18]F-fluoro-2-deoxy-D-glucose positron emission tomography complements conventional imaging for staging lung cancer although its ability to predict outcome is less well established. Two literature-based meta-analyses suggest a prognostic value in univariate analysis. To assess FDG-PET value in predicting survival adjusted for some known prognostic factors, we carried out a meta-analysis based on individual patients data from multiple independent studies.

      Methods
      Following literature search, and after writing of a protocol for the meta-analysis, we contacted the authors of identified studies and requested individual patients data; we also tried to collect some unpublished data. Data analysis used Cox regression models stratified for the study with overall survival as primary outcome. SUV max was used as a binary covariate (median value for each study).

      Results
      Data were collected for 1526 patients (57% of the identified patients) from 11 publications and 1 unpublished series (median age : 64 years, 60% male patients, squamous cell in 34%, adenocarcinoma in 47%, stages I-II in 58%). Combined univariate hazard ratio (HR) was 1.43 (95% CI : 1.22-1.66); no statistically significant interaction between SUV and one of six additional freatures (age, gender, histology,stage, tumors size –in stages I-III patients- and surgical treatment), was found except for stage (p=0.05) with a decreased prognostic value of SUV for stage IV patients. Without considering SUV, multivariate analysis identified, in stage I-III patients, age, stage, tumor size and surgical treatment as independent prognostic factors. The addition of SUV improved that model : HR estimate for SUV effect was 1.58, statistically significant (95% CI : 1.27-1.96), p<0.0001. No interaction was found with SUV. When tumor size was not included in the tested covariates, we found SUV of additional value (adjustment for age, stage, surgical treatment) with a HR of 1.35 (95% CI : 1.15-158). Interaction between SUV and stage was detected, restricting the significant impact of SUV on survival to stage I-III patients.

      Conclusion
      Conclusions : Although suffering from selection bias and lack of homogeneous SUV assessment, these data suggest that SUV at the time of diagnosis is an independent prognostic marker for patients with stage I-III NSCLC. The utility of SUV in predicting survival in stage IV patients requires further studies.

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    P1.08 - Poster Session 1 - Radiotherapy (ID 195)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      P1.08-022 - Number of pathologic nodes in regions closest to the oesophagus is the strongest predictor for esophagitis in small cell lung cancer patients treated with concurrent chemo-radiation: an analysis of 170 patients. (ID 2711)

      09:30 - 09:30  |  Author(s): A. Van Baardwijk

      • Abstract

      Background
      Radiation esophagitis grade III caused by chemo-radiation for small-cell lung cancer is a burden for patients and thus of concern to radiation oncologists. Neutropenia and radiation dose to the esophagus are known treatment factors influencing the rate of esophagitis during treatment, but currently the only factors that can be discussed with the patient at diagnosis are the choice of concurrent versus sequential chemo-radiation and the radiation dose fractionation schedule. In order to build predictive models to more accurately tailor treatment and advise patients on treatment options, more prognostic factors known at the moment of diagnosis are needed.

      Methods
      Analysis of all patients in our prospective database with stage I-III SCLC referred for concurrent chemo-radiotherapy between 5-2004 and 1-2012. All patients were PET-staged and received 45 Gy in 1.5 Gy fractions twice daily to the tumour and PET-or pathologically proven positive lymph nodes. Chemotherapy consisted of carboplatin-etoposide given concurrently with radiotherapy. All pathological lymph node regions were noted for each patient. Based on the Mountain Dressler atlas, the lymph node regions closest to the oesophagus were designated ``high risk`` regions for esophagitis, namely: 1R, 1L, 3P, 4L, 7, 8 and 9. Toxicity was scored according to CTC AE 3.0. Univariate analysis was done using the Chi-square test, reporting for p-value the Fischer exact Test for small numbers of events. Multivariate analysis was done using logistic regression. .

      Results
      170 patients were included in the present analysis. Thirty-seven (20%) patients developed grade III esophagitis. In univariate analysis the number of nodal regions (0, 1-4, ≥5) (p=0.02) and the number of high risk nodal regions (0, 1-2, ≥3) (p=0.001) had a significant effect on the risk of grade III esophagitis whereas the location of the primary tumour or having a T4 tumour did not. In multivariate analysis including age, gender and T4 tumour, the number of pathological nodal stations lost significance. In the multivariate analysis using age, gender, T4 tumour and the ``high risk`` count (0, 1-2, ≥3 areas) having nodes in ≥3 high risk areas was the only significant factor (p=0.002), with a hazard ratio (HR) of 7.4 for developing oesophagitis grade III (95% CI for HR: 2.2-25.2). The absolute rates of esophagitis grade III were: 5/51 (10%), 19/91 (21%), 12/28 (43%) for patients with respectively 0, 1-2 and ≥3 pathological high risk nodal areas.

      Conclusion
      In this series of stage I-III small cell lung cancer treated with radical chemo-radiation, the strongest predictor for esophagitis grade III known at diagnosis is the presence of nodal disease in ``high-risk regions`` 1R, 1L, 3P, 4L, 7, 8 and 9. Analysis of the correlation of this finding with the dose to the esophagus (Dmax/ Dmean) is ongoing and will also be presented at the conference.