Assessment of iodine uptake by pancreatic cancer following chemotherapy using dual-energy CT

Abstract

Pancreatic cancer remains a major health problem, and only less than 20% of patients have resectable disease at the time of initial diagnosis. Systemic chemotherapy is often used in the patients with borderline resectable, locally advanced unresectable disease and metastatic disease. CT is often used to assess for therapeutic response; however, conventional imaging including CT may not correctly reflect treatment response after chemotherapy. Dual-energy (DE) CT can acquire datasets at two different photon spectra in a single CT acquisition, and permits separating materials and extract iodine by applying a material decomposition algorithm. Quantitative iodine mapping may have an added value over conventional CT imaging for monitoring the treatment effects in patients with pancreatic cancer and potentially serve as a unique biomarker for treatment response. In this pictorial essay, we will review the technique for iodine quantification of pancreatic cancer by DECT and discuss our observations of iodine quantification at baseline and after systemic chemotherapy with conventional cytotoxic agents, and illustrate example cases.

Keywords: Chemotherapy; Dual-energy CT; Iodine uptake; Pancreatic adenocarcinoma; Treatment response.

Fig. 1.

Example of tumor segmentation and iodine uptake measurement. Arterial phase CT image and iodine overlay image displayed side by side. Automated segmentation was followed by manual editing through the entire tumor volume. Tumor was segmented and color displayed. Aortic iodine uptake acquired by placing ROI over the aorta was used to obtain normalized tumor iodine uptake.

Fig. 2.

A 73-year-old woman with unresectable adenocarcinoma of the neck of the pancreas with encasement of celiac axis and portal vein/SMV confluence, treated with gemcitabine, taxotere, and xeloda. Tumor diameter decreased to 89% of the baseline, tumor volume 53%, and CA19–9 10%. A Baseline arterial and B venous phase CT. C Post-chemotherapy arterial and D venous phase CT. Tumor iodine uptake and normalized tumor iodine uptake were A 1.6 mg/mL and 8%, B 2.7 mg/mL and 50%, C 1.0 mg/mL and 7%, and D 1.0 mg/mL and 29%.

Fig. 3.

A 73-year-old woman with unresectable pancreatic adenocarcinoma with encasement and occlusion of the portal vein/SMV confluence, treated with FOLFIRINOX. Tumor diameter decreased to 85% of the baseline, tumor volume 59%, and CA19–9 47% after chemotherapy. A Baseline arterial and B venous phase CT. C Post-chemotherapy arterial and D venous phase CT. Tumor iodine uptake and normalized tumor iodine uptake were A 1.0 mg/mL and 6%, B 1.6 mg/mL and 45%, C 0.4 mg/mL and 3%, and D 1.3 mg/mL and 21%.

Fig. 4.

A 47-year-old man with pancreatic adenocarcinoma arising from the pancreatic neck with encasement of the celiac axis and common hepatic artery, treated with FOLFIRINOX. Tumor diameter decreased to 75% of the baseline, tumor volume 57%, and CA19–9 70%. A Baseline arterial and B venous phase CT. C Post-chemotherapy arterial and D venous phase CT. Tumor iodine uptake and normalized tumor iodine uptake were A 1.5 mg/mL and 23%, B 1.7 mg/mL and 43%, C 1.4 mg/mL and 13%, and D 1.6 mg/mL and 38%. After completion of chemotherapy, patient had radiation therapy followed by pancreaticoduodenectomy. Pathology revealed 0.5 cm poorly differentiated adenocarcinoma in the pancreas and an area of dense scarring associated with large blood vessels, ganglia, and nerve trunks without remaining tumor.

Fig. 5.

A 65-year-old man with unresectable adenocarcinoma of the body of the pancreas encasing the celiac axis and superior mesenteric artery, and extending around the aorta, treated with gemcitabine and cisplatin. Tumor diameter was nearly unchanged (98% of the baseline), tumor volume mini mally decreased to 88% and CA19–9 70%. A Baseline arterial and B venous phase CT. C Post-chemotherapy arterial and D venous phase CT. Tumor iodine uptake and normalized tumor iodine uptake were A 1.0 mg/mL and 12%, B 1.1 mg/mL and 28%, C 0.9 mg/mL and 11%, and D 1.1 mg/mL and 27%.

Fig. 6.

A 75-year-old man with borderline resectable adenocarcinoma of the head of the pancreas with borderline vascular encasement, treated with FOLFIRINOX. Tumor size was unchanged (tumor diameter 100% of the baseline, tumor volume 98%), and CA19–9 93% of the baseline after chemotherapy. A Baseline arterial and B venous phase CT. C Post-chemotherapy arterial and D venous phase CT. Tumor iodine uptake and normalized tumor iodine uptake were A 1.3 mg/mL and 20%, B 1.4 mg/mL and 31%, C 1.4 mg/mL and 12%, and D 1.6 mg/mL and 36%.

Fig. 7.

A 65-year-old man with unresectable adenocarcinoma of the body of the pancreas which encases and occludes the portal vein/SMV confluence, and encases the SMA and celiac axis, treated with FOLFIRINOX switched to gemcitabine/abraxane due to poor tolerance. Tumor diameter increased to 117% of the baseline, tumor volume 184%, and CA19–9 540% after chemotherapy. Peritoneal carcinomatosis with ascites developed on post-chemotherapy CT. A Baseline arterial and B venous phase CT. C Post-chemotherapy arterial and D venous phase CT. Tumor iodine uptake and normalized tumor iodine uptake were A 1.0 mg/mL and 9%, B 1.5 mg/mL and 41%, C 1.2 mg/mL and 8%, and D 2.4 mg/mL and 38%.