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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
MO23.02 - Quantification of radiation-induced lung damage with CT scans: The possible benefit for radiogenomics (ID 254)
10:30 - 12:00 | Author(s): H. Sharifi
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.
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.
95 lung cancer patients were studied. Radiation dose was linearly correlated with the change in HU (mean R=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
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
- Coordinates: 10/29/2013, 09:30 - 16:30, Exhibit Hall, Ground Level
P2.06-030 - Radiation-induced lung damage quantification with CT scans: Correlation with single nucleotide polymorphisms (ID 2420)
09:30 - 16:30 | Author(s): H. Sharifi
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.
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.
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
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.