Lung fibrosis development is a commonly observed finding on computerized tomography (CT) imaging following Stereotactic Body Radiation Therapy (SBRT) for lung cancer. However, the severity of the fibrosis is widely variable, and there is limited data with regards to predictive factors. The purpose of this study is to investigate the association between patient and treatment related factors on the severity of radiation induced fibrosis (RIF) development via a radiomic analysis of post treatment CT scans following SBRT. Materials/Methods: Under an Institutional Review Board-approved protocol, the records of consecutive patients treated from 2012 e 2015 at 4 related academic institutions with lung SBRT were reviewed. 58 patients who had CT imaging available from 11-13 months post treatment were analyzed. A single radiation oncologist delineated the volume of fibrosis on each CT. A multivariable radiomic analysis was performed to describe the characteristics of the fibrosis. Total fibrosis mass (TFM) was determined for each volume. The density within each fibrotic volume was derived from mean Hounsfield unit; and TFM was the product of density and delineated volume. TFM was used as the surrogate for fibrosis severity. Univariate analysis was performed to identify relevant co-variates of RIF severity. Results: Median age at treatment was 71 years old. 58% of patients were female, 74% were white, and 29% were active smokers with median 50 pack-year history. Median tumor size was 1.8 cm and 58% of tumors peripherally located. Total radiation dose ranged from 40-54 Gy (median 48 Gy), delivered in 3-5 fractions (fx) (median 4 fx), for a dose per fx between 8-18 Gy (median 12 Gy/fx). Median TFM was 158.7g (range 0.93 e 2,328.3g). Factors which were significantly correlated with TFM severity included tumor size (pZ0.025), planning target volume (PTV) (pZ0.001), volume receiving 100% prescribed dose (V100%) (p<0.001), V50% (pZ0.007), mean lung dose (pZ0.003), lung V5 (volume of lung receiving 5 Gy) (pZ0.006), V10 (pZ0.008), V12 (pZ0.014), V15 (pZ0.024), and V20 (pZ0.019). Total Dose, dose per fx, R50 (the ratio of the 50% isodose line/PTV), conformality index and maximum dose 2cm from tumor were notably not related to TFM. Patient age, sex, race, active smoking status, pack-year history and the peripheral vs. central location were not significantly associated with TFM severity. Conclusion: Several treatment planning parameters and lung dose volume metrics were significantly correlated with the severity of radiation induced fibrosis development following SBRT. Patient factors did not appear to significantly contribute to fibrosis development. Further study of treatment and patient related factors associated with RIF over time is underway.
in the Arm D as compared with the Arm A group. Further analysis showed that high-dose radiation therapy showed longer median survival time than standard dose (PFS, 35.0 vs 19.0m, pZ0.092, LRRFS, 35.0 vs 22.0m, pZ0.063, OS, 35.0 vs 22.0, pZ0.063). However, comparison of the groups having ENI with those receiving IFI showed no significant difference in survival. Within the Arm A, Arm B, Arm C and Arm groups, 10.1%, 6.5%, 4.2% and 4.4% had grade 3/4 neutropenia , respectively (pZ0.034).There were no significant differences in the incidence of severe (grade3) acute esophagitis, pneumonitis/ radiation pneumonitis or thrombocytopenia between the 4 treatment groups. Conclusion: Although there was a higher LRRFF and PFS rate in esophageal cancer patients with concurrent chemoradiotherapy receiving higher radiation dose with IFI), but no statistical difference was found in OS. Further recruitment and follow-up are needed.
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