Purpose: Dual-source dual-energy CT (DECT) data can be used to calculate the extracellular volume fraction (ECVf) in tumors, which has been correlated with treatment outcome. In this work, we seek to find a correlation between ECVf and change in Carbohydrate Antigen (CA) 19-9 as a surrogate for treatment response for chemoradiation therapy (CRT) of pancreatic cancer.
Methods: DECT data at the late arterial contrast phase acquired in the standard simulation on a dual-source DECT simulator for 22 pancreatic cancer patients, along with their CA19-9 and hematocrit data, were analyzed. Each patient underwent CRT with a prescription of 50.4Gy in 28 fractions. The patients were chosen based on the presence of a solid tumor in the pancreas which could be clearly delineated. A region of interest (ROI) was placed in the tumor and in the aorta. From the ratio of the Iodine density calculated from the DECT in the ROI and the hematocrit taken at the time of simulation, the ECVf was calculated. The ECVf was then compared to the change in CA19-9 before and after the CRT. Distant metastases as the cause of CA 19-9 elevation were ruled out on subsequent restaging studies prior to surgery. The DECT derived iodine ratio was validated using a phantom study.
Results: The average hematocrit, ECVf, and change in CA19-9 during the treatment for the 22 patients was 35.6±5.4%, 7.3±4.9% and -4.6±21.8 respectively. We found a linear correlation between the ECV fraction and the change in CA19-9 with an R² of 0.7: ΔCA19-9 = 3.63×ECVf – 31.1. The correlation was statistically significant (P=0.006). The DECT derived iodine concentration agreed with the phantom measurements (R²=1.0).
Conclusion: The pre-treatment ECV fraction obtained based on Iodine maps from dual-source DECT may be used to predict treatment response for adjuvant chemoradiation therapy of pancreatic cancer.
Funding Support, Disclosures, and Conflict of Interest: Research partially supported by Siemens