Room: Stars at Night Ballroom 2-3
Purpose: The goal of this study is to investigate whether a combination of delta-radiomic-features (DRF) and the commonly used tumor characteristic factors, carbohydrate-antigen (CA19-9) and carcinoembryonic-antigen (CEA), is an improved biomarker for CRT response of locally advanced unresectable pancreatic cancer (LAUPC).
Methods: Daily non-contrast CTs (28-fractions) acquired during routine CT-guided CRT for 20 LAUPC patients, along with their CA19-9, and CEA-tests were analyzed. The pancreatic head was delineated on daily CTs and DRFs were extracted. DRFs were examined to find response correlation in LAUPC using t-test and linear-mixed-effect-models. The time from the end of treatment until endpoint of death or presence of distant metastases were used to build a survival model. Patients not reaching the endpoint were censored at their last follow-up date. Univariate and multivariate Cox regression analysis were performed to determine the effect of combining CA19-9, CEA, and DRFs on survival-probability. The effect of normalized (or a decrease) in CA19-9 and CEA-levels during treatment versus failure of CA19-9 and CEA-levels to normalize (or an increase) on survival was examined.
Results: The univariate analysis showed that patients with decreasing-CA19-9 had an improved median survival (12month) compared to those with increasing-levels (4month). Six DRFs were correlated to response in LAPC. The multivariate Cox regression analysis showed that a treatment related decrease in CA19-9 levels (p=0.03), CEA-levels (p=0.05) and DRFs (p=0.02-0.05) were predictors of survival. Incorporating CA19-9 with DRFs increased the concordance-statistic from 0.51 to 0.75. The c-index further increased to 0.81 combining CEA to CA199 and DRFs. The hazard-ratio was reduced from 0.69, p=0.03 using CA19-9 only and 0.71 using CEA only to 0.43, p=0.04 combining DRFs with CA19-9, this was further reduced to 0.27, p=0.02 combining DRFs with CA19-9 and CEA.
Conclusion: The combination of CT delta-radiomics, CA19-9 and CEA is an improved biomarker for CRT response of LAUPC.