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W. Van Elmpt



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

      10:30 - 12:00  |  Author(s): W. Van Elmpt

      • 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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    P2.06 - Poster Session 2 - Prognostic and Predictive Biomarkers (ID 165)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P2.06-030 - Radiation-induced lung damage quantification with CT scans: Correlation with single nucleotide polymorphisms (ID 2420)

      09:30 - 16:30  |  Author(s): W. Van Elmpt

      • Abstract

      Background
      Radiation-induced lung damage (RILD) is a dose-limiting toxicity of lung radiotherapy. Individual sensitivity can be measured by changes in Hounsfield Units over time (delta HU) on CT scans (De Ruysscher et al. Acta Oncol 2013). This endpoint is specific for lung damage and does not correlate with dyspnoea, which is multi-factorial. In this study, we investigated the association between density changes over time and SNPs aiming at finding individual sensitivity for RILD.

      Methods
      Delta HU/Gy and delta HU/Gy x MLD (Mean Lung Dose), the latter to take into account a volume factor for RILD, were correlated with 314 SNPs related to fibrosis and inflammation. The outcome variables were square root transformed because both were not normally distributed. Univariate ANOVA analyses were performed for comparisons of means. P-values of less than 0.01 were considered to be significant.

      Results
      Eighty-nine lung cancer patients were studied, 63 men and 26 females. Twenty patients were treated with radiotherapy alone, 31 with sequential chemo-RT and 38 with concurrent chemo-RT. Twenty percent of the patients developed grade 2 or more clinical dyspnoea after treatment. Three SNPs were significantly correlated with delta HU/Gy: rs2252070 (p=0.006, MMP13), rs2230588 (p=0.009, JAK1) and rs12901071 (p=0.009, SMAD3) [Table 1A]. For delta HU/Gy x MLD, significant associations were found for rs3819122 (p=0.008, SMAD4), rs2230529 (p=0.009, ITGB2) and rs2230588 (p=0.009, JAK1) [Table 1B]. Figure 1

      Conclusion
      Quantification of CT density changes due to radiotherapy, measured as HU changes over time as a specific and quantitative endpoint for RILD correlates with specific SNPs in genes involved in signal transduction of cytokines (SMAD3/4, JAK1), in the extracellular matrix (MMP13) and in cell adhesion (ITGB2). External validation will follow.

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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 - 16:30  |  Author(s): W. Van Elmpt

      • 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.