EUS Utility Varies Among Gastrointestinal Cancers

Q: When Is EUS Necessary for a Newly Diagnosed Cancer of the Esophagus, Stomach, Colon, or Pancreas?

Issue: June 2017

ByThomas J. Savides, MD

A: Gastrointestinal endoscopic ultrasound (EUS) is an important tool for cancer staging because many treatment algorithms are determined by EUS tumor staging. Computed tomography (CT) scan should generally be obtained before EUS to determine whether there is any metastatic disease that would make the patient a nonsurgical candidate. If there is no evidence of metastatic disease, then EUS should be performed for locoregional staging. The tumor-node-metastases (TNM) staging system is used for luminal GI and pancreatic cancer. The EUS accuracy for staging GI and pancreatic cancer is approximately 85% for T-staging and 75% for N-staging. EUS-guided fine needle aspiration (EUS FNA) can be used to obtain tissue diagnosis of tumors as well as peritumoral metastatic disease.

The time to use EUS in cancer staging is before the patient receives any chemoradiation. Staging accuracy significantly decreases after chemoradiation because EUS cannot distinguish between peritumoral inflammation/edema and the actual tumor.

Esophageal Cancer

If EUS shows that a tumor is limited to the mucosal layer (tumor in-situ) and without any adjacent lymph nodes (N0), then it is potentially amenable to endoscopic resection. Endoscopic mucosal resection is the only accurate way to know for certain if the tumor is limited to the mucosal layer. Esophageal tumors that invade into the submucosal layer have an approximate 15% risk of metastatic disease to regional lymph nodes and should generally undergo surgical resection with lymph node dissection.

If EUS reveals there is invasion into the periesophageal fat (T3) or periesophageal regional lymph nodes (N1), then the patient is generally referred for preoperative chemoradiation. Patients with involvement into adjacent organs such as the aorta, heart, or trachea (T4) are usually not considered surgical candidates. I do not perform EUS restaging after chemoradiation because it is not accurate and there is no established algorithm for treatment management.

EUS FNA can be performed to increase the lymph node staging accuracy in esophageal cancer. However, often this is not possible due to the lymph nodes being located in a position whereby the needle would need to pass through the tumor to reach the lymph node.

Figure 1. Gastric MALT lymphoma. Note the thickening of the mucosal and submucosal layers.

Gastric Cancer

The utility of EUS is limited to evaluating superficial cancer to determine whether it is potentially amenable to endoscopic resection. Patients with tumors limited to the mucosa/submucosa (T1) and without adjacent lymph nodes (N0) are candidates for endoscopic resection. For more advanced tumors, there is no need for EUS because these patients will generally undergo surgical resection. Occasionally, it may be worthwhile to do an EUS in advanced tumors to determine whether there is invasion into an adjacent organ, such as the pancreas. In the rare cases of gastric mucosa-associated lymphoid tissue (MALT) lymphoma, EUS can identify the tumors limited to the mucosa/submucosa, which are most likely to possibly respond to antibiotic therapy for Helicobacter pylori infection (Figure 1).

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Colorectal Cancer

EUS is useful only in rectal cancer; it is not helpful in colon cancer. This is because for colon cancer, the surgeon can obtain wide distal, proximal, and lateral margins. In contrast, the location of rectal cancer in the pelvis precludes extended longitudinal or circumferential surgical margins, which results in a higher risk of locally recurrent tumor after resection. In addition, because of the fixed position of the rectum in the pelvis, rectal cancer is amenable to radiation therapy.

If EUS shows that the rectal tumor involves only the mucosa/submucosa (T1, N0), then it is amenable to surgical transanal resection. If the tumor extends into the perirectal fat (T3) and/or has associated malignant-appearing lymph nodes (N1), then generally patients are offered preoperative chemoradiation (Figure 2). EUS is not routinely performed after chemoradiation for rectal cancer. If a patient undergoes transanal resection of a rectal cancer, then I perform follow-up transrectal ultrasound every 6 months for a total of 2 years to detect any local recurrence.

Figure 2. Rectal cancer — stage T3, N1. Note that the tumor extends into the perirectal fat (T3), and there is a malignant-appearing lymph node adjacent to the mass (N1).

Pancreatic Cancer

The utility of EUS is somewhat less important for staging pancreatic cancer than esophageal or rectal cancer. This is because initially EUS was better than old-generation CT scanners for determining locally advanced pancreatic cancer, although more recent multidetector CT scans have similar staging accuracies as EUS. In addition, there are no agreed-upon criteria for locally unresectable pancreatic cancer. Invasion of the portal vein (Figure 3), superior mesenteric vein, or superior mesenteric artery is generally considered a contraindication to surgery; however, many experienced pancreatic surgeons can often peel pancreatic tumors off blood vessels and perform vascular reconstructions for locally invasive cancer. Therefore, in my center, I usually obtain a pancreatic protocol multidetector CT scan rather than an EUS to determine whether there are any absolute contraindications to surgery, such as significant encasement of the celiac artery or superior mesenteric artery. There are some centers where more emphasis is placed on the EUS assessment of vascular involvement, although I suspect that multidetector CT scans and MRI scans will continue to be as good as or better than EUS for predicting respectability. In the end, the only true way to know whether a pancreatic tumor is resectable is by attempted surgical resection by an expert pancreatic surgeon.

I believe the most important role of EUS in pancreatic cancer is actually visualizing the pancreatic mass (sometimes CT shows only bile duct obstruction or fullness in the pancreatic masses) and for obtaining FNA cytology tissue diagnosis of malignancy. In the future, EUS-guided fine needle injection may be used for pancreatic cancer treatment, either by directly injecting antitumor drugs or by injecting radiopaque markers into the tumor to assist with radiation therapy.

Excerpted from:

References:
DeWitt J, et al. Ann Intern Med. 2004;141(10):753-763.
Sackmann M, et al. Gastroenterology. 1997;113(4):1087-1090.
Savides TJ, Master SS. Gastrointest Endosc. 2002;56(4 Suppl):S12-S18.
Vazquez-Sequeiros E. et al. Gastroenterology. 2003;125(6):1626-1635.

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