Margin-negative surgical resection is the only potentially curative technique for pancreatic cancer. Patients with margin-positive resections; with visceral, peritoneal, or pleural metastases; or with metastases to nodes beyond the field of resection derive no benefit from resection.5–7
Accurate determination of resectability is therefore critical for the optimal management of pancreatic cancer. Unlike many other cancers, imaging is the primary means through which the stage of pancreatic cancer is determined. Therefore, high-quality multiphase diagnostic imaging, which can help to preoperatively distinguish between patients eligible for resection with curative intent and those with unresectable disease, is essential.
Pancreatic protocol CT is the most widely available and best-validated imaging modality for staging patients with pancreatic cancer.8,9
Studies have shown that 70% to 85% of patients determined to have resectable tumors through CT were able to undergo re-section.8,10–14
During the institutional review of the NCCN Guidelines, a reviewer suggested that pancreas protocol MRI should also be listed as an option for diagnostic staging. Panelists confirmed that pancreas protocol MRI is emerging as an equivalent alternative to CT (see PANC-1). Some NCCN Member Institutions, in fact, now prefer MRI over CT imaging because of concerns regarding radiation dose over time with CT scans. Most NCCN Member Institutions, however, use CT and MRI interchangeably. In fact, comparisons show that the 2 modalities are similar in their ability to predict vessel and node involvement.15–18
MRI may be superior to CT for detecting small hepatic and peritoneal metastases,18,19
and therefore may also be a helpful adjunct to CT in high-risk patients if CT is initially performed and no metastases are found.
The institutional review also included a request for more details regarding optimal multiphase imaging techniques. The discussion that ensued centered on the thickness at which images are captured and rendered. The consensus among the panelists was that cuts should be thin, at 3 mm or less. The panelists agreed that optimal multiphase imaging technique (CT or MRI) includes a noncontrast phase plus arterial, pancreatic parenchymal, and portal venous phases of contrast enhancement with thin cuts (≤ 3 mm) through the abdomen. This technique allows precise visualization of the relationship of the primary tumor to the mesenteric vasculature and detection of metastatic deposits as small as 3 to 5 mm (see PANC-A).8,12,20,21
The difference in contrast enhancement between the parenchyma and adenocarcinoma is highest during the late arterial phase, thereby providing a clear distinction between a hypodense lesion in the pancreas and the rest of the organ. A multiphasic pancreatic protocol allows for selective visualization of important arterial (e.g., celiac axis, superior mesenteric artery, and peripancreatic arteries) and venous structures (e.g., superior mesenteric vein, splenic vein, and portal vein), thereby providing an assessment of vascular invasion by the tumor.
All of this information can improve the prediction of resectability. Software allowing for 3-dimensional reconstruction of imaging data can provide additional valuable information on the anatomic relationship between the pancreatic tumor and the surrounding blood vessels and organs, although the panelists agreed that further development of this technology is needed before it is routinely integrated into clinical practice.13
Patients commonly present to the oncologist with a non–pancreas protocol CT already performed. The panelists agreed that if the CT scan is of high quality, it can be sufficient. If not, a pancreas protocol CT or MRI is recommended.22