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S. Peeters



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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: 2
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      MO23.02 - Quantification of radiation-induced lung damage with CT scans: The possible benefit for radiogenomics (ID 254)

      10:30 - 12:00  |  Author(s): S. Peeters

      • Abstract
      • Presentation
      • Slides

      Background
      Radiation-induced lung damage (RILD) is an important problem. Although physical parameters such as the mean lung dose are used in clinical practice, they are not suited for individualised radiotherapy. As radiosensitivity varies between patients, genetic correlations have been investigated, which appear to be difficult to repeat in validation studies. This may be due, in part, to differences in methods for measuring RILD across studies. Objective, quantitative measurements of RILD on a continuous instead of on an ordinal, semi-quantitative, semi-subjective scale, are needed.

      Methods
      Hounsfield Unit (HU) changes before vs. 3 months post-radiotherapy were correlated per voxel with the radiotherapy dose. Deformable registration was used to register pre and post CT scans and the density increase was quantified for various dose bins. The dose-response curve for increased HU was quantified using the slope of a linear regression (HU/Gy). The end-point for the toxicity analysis was dyspnoea ≥ grade 2.

      Results
      95 lung cancer patients were studied. Radiation dose was linearly correlated with the change in HU (mean R[2]=0.74 ± 0.28). No differences in HU/Gy between groups treated with stereotactic radiotherapy, conventional radiotherapy alone, sequential or concurrent chemo-radiotherapy were observed. In the whole patient group, 33/95 (34.7 %) had dyspnoea ≥ G2. Of the 48 patients with a HU/Gy below the median, 16 (33.3 %) developed dyspnoea ≥ G2, while in the 47 patients with a HU/Gy above the median, 17 (36.1 %) had dyspnoea ≥ G2 (not significant). Individual patients showed a nearly 21-fold difference in radiosensitivity, with HU/Gy ranging from 0 to 10 HU/Gy. Figure 1

      Conclusion
      HU changes identify objectively the whole range of individual radiosensitivity on a continuous, quantitative scale. CT density changes may allow more robust and accurate radiogenomics studies.

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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)

      10:30 - 12:00  |  Author(s): S. Peeters

      • 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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    P2.04 - Poster Session 2 - Tumor Immunology (ID 154)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P2.04-002 - Differential expression of PD-L1, PD1 and CTLA4 receptor according to histology and tumour vs. surrounding non-malignant lung tissue in non-small cell lung cancer: RNA sequencing data (ID 2427)

      09:30 - 16:30  |  Author(s): S. Peeters

      • Abstract

      Background
      Immune modulatory strategies directed against CTLA4 (Cytotoxic T-Lymphocyte Antigen 4), PD1(Programmed cell Death 1) and PD-L1 (Programmed cell Death 1 Ligand 1) either in monotherapy or in combination with chemotherapy and radiotherapy offer great promise as novel treatments against lung cancer. Its outcome and therapeutic ratio may depend on the expression of the target molecules in tumours and the surrounding non-malignant lung tissue. We here report the expression of CTLA4, PD1 and PD-L1 in primary resected NSCLC and in the surrounding non-malignant lung.

      Methods
      RNA sequencing was performed on tumor tissue and normal lung tissue from resection specimens of NSCLC patients. The association between CTLA4, PD1 and PD-L1 expression levels and histology, gender, age, smoking status (current smoker vs. smoking cessation of at least one year), COPD and CRP blood levels was calculated both in the primary tumour and the normal lung. Results are expressed as mean +/- SD and range. Means were compared using Wilcoxon’s signed rank test for the distributions were non-parametrical. P-values <0.05 were considered significant.

      Results
      Fourteen patients were studied, 11 males and 3 females, with a mean age of 64.6 +/- 10.0 years (41-79). All patients had a smoking history: 6 were current smokers, 8 former smokers. COPD status: 8 no COPD, 1 GOLD class I, 3 GOLD class II, 2 GOLD class III. Pre-operative CRP (mg/dL): 15.0 +/- 2.9 (0.20-54.7). Seven patients had squamous cell cancer, 7 adenocarcinoma. PD-L1 expression in the lung was 3833 +/- 787 (372-5072), PD-L1 in the tumour 2595 +/- 1657 (788-6689), with a tumour/lung ratio of 0.67 +/- 0.37 (0.21-1.32). PD-L1 squamous vs. adenocarcinoma was 1840 +/- 1012 vs. 3350 +/- 1896, p<0.001. PD-L1 in the lung of ex-smokers vs. current smokers: 4136 +/- 811 vs. 3430 ± 591, p<0.001. These associations were not found for CTLA4 and PD1 receptor: CTLA4 tumour squamous vs. adenocarcinoma: 100.9 +/- 46.3 vs. 95.3 +/- 73.6, p=0.86; CTLA4 lung smokers vs. ex-smokers: 78.4 +/- 41.3 vs. 107.0 +/- 75.1, p=0.75. PD1 receptor tumour squamous vs. adenocarcinoma: 591 +/- 244 vs. 689 +/- 263, p=0.31 PD1 receptor in the lung of smokers vs. ex-smokers: 599 +/- 278 vs. 695 +/-216, p=0.46. No associations between CTLA4, PD1 and PD-L1 in the tumour or the lung and gender, age, COPD and CRP blood levels were found.

      Conclusion
      RNA sequencing is a useful method to dissect relevant molecules in the tumour and the lungs. Our results show more PD-L1 expression in adenocarcinoma than in squamous cell cancer, more PD-L1 expression in the non-malignant lung of ex-smokers than in current smokers and reduced PD-L1 in tumours compared to adjacent lung tissue.

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    P2.08 - Poster Session 2 - Radiotherapy (ID 198)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      P2.08-002 - Modern post-operative radiotherapy for stage III non-small cell lung cancer may improve local control and survival: A publication-based meta-analysis (ID 89)

      09:30 - 16:30  |  Author(s): S. Peeters

      • Abstract

      Background
      We hypothesized that modern postoperative radiotherapy (PORT) could decrease local recurrence (LR) and improve overall survival (OS) in patients with stage IIIA-N2 non-small-cell lung cancer (NSCLC).

      Methods
      To investigate the effect of modern PORT on LR and OS, we identified published phase III trials for PORT and stratified them according to use or non-use of linear accelerators. We modelled the potential benefit of modern PORT in stage IIIA-N2 NSCLC treated with induction chemotherapy and resection.

      Results
      Of the PORT phase III studies, eleven trials (2387 patients) were included for OS analysis and eight (1677 patients) for LR. PORT decreased LR, whether given with cobalt, cobalt and linear accelerators, or with linear accelerators only. An increase in OS was only seen when PORT was given with linear accelerators, along with the most significant effect on LR (relative risk for LR and OS 0.31 (p=0.01) and 0.76 (p=0.02) for PORT vs. controls, respectively). Four trials (357 patients) were suitable to assess LR rates after surgery and/or induction chemotherapy in stage III NSCLC. LR as first relapse was 30 % (105/357) after 5 years. In the modelling part, PORT with linear accelerators was estimated to reduce LR rates to 10 % as first relapse and to increase the absolute 5-year OS by 13 %.

      Conclusion
      This modelling study generates the hypothesis that modern PORT may increase both LR and OS in stage IIIA-N2 NSCLC even in patients being treated with induction chemotherapy and surgery.