External validation of a prognostic CT-based radiomic signature in XXXX .

@entity5 @entity135 @entity957 @entity1
UNASSIGNED: @entity957 ( @entity957 ) is one of the fastest growing disease sites of @entity135 . A recently described radiomic signature, based exclusively on pre-treatment computed tomography (CT) imaging of the primary @entity5 volume, was found to be prognostic in independent cohorts of lung and @entity135 @entity1 treated in the Netherlands. Here, we further validate this signature in a large and independent North American cohort of @entity957 @entity1 , also considering CT artifacts. METHODS: A total of 542 @entity957 @entity1 were included for which we determined the prognostic index (PI) of the radiomic signature. We tested the signature model fit in a Cox regression and assessed model discrimination with Harrell's c-index. Kaplan-Meier survival curves between high and low signature predictions were compared with a log-rank test. Validation was performed in the complete cohort (PMH1) and in the subset of @entity1 without (PMH2) and with (PMH3) visible CT artifacts within the delineated @entity5 region. RESULTS: We identified 267 (49%) @entity1 without and 275 (51%) with visible CT artifacts. The calibration slope (b) on the PI in a Cox proportional hazards model was 1.27 (H0: b = 1, p = 0.152) in the PMH1 (n = 542), 0.855 (H0: b = 1, p = 0.524) in the PMH2 (n = 267) and 1.99 (H0: b = 1, p = 0.002) in the PMH3 (n = 275) cohort. Harrell's c-index was 0.628 (p = 2.72e-9), 0.634 (p = 2.7e-6) and 0.647 (p = 5.35e-6) for the PMH1, PMH2 and PMH3 cohort, respectively. Kaplan-Meier survival curves were significantly different (p < 0.05) between high and low radiomic signature model predictions for all cohorts. CONCLUSION: Overall, the signature validated well using all CT images as-is, demonstrating a good model fit and preservation of discrimination. Even though CT artifacts were shown to be of influence, the signature had significant prognostic power regardless if @entity1 with CT artifacts were included.
