Gastric

Malignant Diseases

Screening endoscopy with biopsy is again regarded as the procedure of choice to evaluate lesions suspicious for carcinoma of the stomach. Except for tumors that do not break through the mucosal surface (e.g., linitis plastica), conventional endoscopy is superior to EUS for diagnosis. EUS has been shown to be more accurate than any nonoperative technique to stage gastric neoplasms [1,15,50]. The accuracy of local staging of gastric neoplasms with EUS is slightly less than for esophageal neoplasms (see Table 2). CT scan is important in evaluating the M stage of disease; however, endoscopic ultrasound is up to 6 times more accurate in staging tumors than CT scan, if one takes into account early lesions that CT scan cannot accurately stage. The thickness of the gastric wall can be affected by other pathology, most commonly acute and chronic inflammation. In addition, small regional lymph nodes are frequently missed by CT. CT scan is useful in evaluating progression of the tumor beyond regional lymph nodes, such as in the celiac, gastroduodenal, and gastrohepatic sites. When tumors are large enough to distort the gastric anatomy, it may be more difficult to orient the EUS probe to accurately evaluate tumor stage.

For gastric tumors, the clinical utility of EUS is directly related to available stage-dependent treatment. If stage-dependent protocols are applied, EUS staging is mandatory. EUS has been shown to be 85% accurate in predicting resectability. EUS decreases the need for exploratory laparotomy for patients with gastric carcinomas [51].

Prognosis depends on depth of tumor invasion, lymph node metastasis, and distant metastasis. Initial EUS T stage has been shown to correlate with spread to lymph nodes [51], survival, and frequency of recurrence [52] after surgical removal of the lesion (see Table 5; Table 8). In a group of patients who on preoperative staging had nonresectable gastric tumors, 50% were found to be resectable at laparotomy following preoperative chemotherapy. Median survival of these unresectable gastric carcinomas was 24 months with treatment. In another multicenter study comparing postoperative chemotherapy with no treatment, patients with advanced T-stage tumors had a significant increase in 5-year survival with chemotherapy, whereas those with early TI or T2 stage tumors did not benefit [25]. It is unknown whether patients with T2 lesions (Fig 5) will benefit more from radical versus limited resection or how these two different surgical approaches would affect quality of life.

Accuracy for each T and N stage is quite high for EUS: 80% for T 1, 65% for T2, 87% for T3, 79% for T4, 84% for NO, 74% for N 1, and 63% for N2. EUS can detect metastatic spread to distant (N2) lymph nodes [51]. There are, however, certain limitations of EUS staging for gastric carcinomas. Lesions that infiltrate only into the subserosa can be overstaged because associated fibrosis and inflammatory changes or ulceration can obscure the border between the subserosa and the serosa; differentiation between T2 and T3 lesions is therefore difficult, resulting in only a 55% accuracy for T2 lesions [15,36,53]. Parts of the proximal stomach not covered by serosa add to EUS image interpretation difficulties. Ulceration occurring in early carcinoma complicates differentiating malignancy from fibrosis and inflammation with EUS; therefore, carcinomas involving only the mucosa may at times not be distinguished from carcinomas involving the submucosa. This differentiation is important in selecting patients who may be amenable to endoscopic treatment [54,55].

Table 2
Accuracy of GI Tumor Staging and Respectability with EUS and CT^a

		EUS	CT
Esophagus
	T stage	85	60
	N stage	80	55
	M stage	70	85
	Resectability	80	55
Gastric
	T stage	80	40
	N stage	75	50
	M stage	90	80
	Resectability	85	55
Pancreas
	T stage	90	50
	N stage	75	50
	M stage	75	75
	Resectability	85	55
Biliary System
	T stage	85	45
	N stage	60	50
	M stage	85	85
	Resectability	80	60
Rectum
	T stage	85	70
	N stage	80	55
	M stage	…	75

^a Values are median estimates in percent from references in text.

Table 5
Correlation of EUS T Stage with the Presence of Malignant Lymph Nodes ^a

^a Values are median estimates in percent from references in text.

Table 8
Correlation of EUS T Stage with Survival Recurrence of Resected Gastric Carincoma ^a

Data from [52].
^a Median follow-up time of 25 months.

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