A 72-year-old Japanese immigrant was brought in by his family with complaints of difficulty eating, vague abdominal pain, and weight loss. Endoscopy and biopsy confirmed gastric adenocarcinoma (Figure 62-1). Liver metastases were found on abdominal CT. The family and the patient chose only comfort measures, and the patient died 6 months later.
Endoscopy showing a raised and irregular mass in the antrum of the stomach deforming the pylorus. It fills the distal one-half of the antrum. The lesion was hard when probed with biopsy forceps. Biopsy indicated adenocarcinoma. (Reproduced with permission from Michael Harper, MD.)
Gastric cancer, also known as stomach cancer, is a malignant neoplasm of the stomach, usually adenocarcinoma.
Based on Surveillance Epidemiology and End Results (SEER) data (2009–2013), an estimated 26,370 people will be diagnosed with gastric cancer, and 10,730 will die of this cancer in 2016.1 The male-to-female ratio is about 2:1.2 The median age at diagnosis is 70 years (typical range 60–84 years)2 and median age at death from gastric cancer is 73 years.1
Gastric cancer occurs in 7.4 per 100,000 men and women annually. In 2013, an estimated 79,843 people in the United States had gastric cancer, with a lifetime risk of 0.9%.1
Highest rates of gastric cancer occur in eastern Asia, eastern Europe, and South America.2
ETIOLOGY AND PATHOPHYSIOLOGY
Over 90% percent of gastric cancers are adenocarcinomas with the remainder lymphomas, carcinoid tumors, and GI stromal tumors.3
Exogenous and endogenous factors (see "Risk Factors" below) contribute to the development of gastric cancer.2
Genetic factors—Oncogenic pathways identified in most gastric cancers are the proliferation/stem cell, nuclear factor-κB, and Wnt/β-catenin; interactions between them appear to influence disease behavior and patient survival.4 There are several autosomal dominant genetic syndromes associated with gastric cancer—hereditary diffuse gastric cancer caused by a germline mutation in the CDH1 gene; Lynch syndrome, which involves defective DNA mismatch repair; juvenile polyposis syndrome; and Peutz-Jeghers syndrome.2,5
Gastric tumors are classified for staging using the T (tumor) N (nodal involvement) M (metastases) system. Two important prognostic factors are depth of invasion through the gastric wall (less than T2 [tumor invades muscularis propria]) and presence or absence of regional lymph node involvement (N0). Changes made to the classification system in the seventh edition of the American Joint Commission's Cancer Staging Manual for gastric cancer demonstrate better survival discrimination.6
Gastric cancer spreads in multiple ways3:
Local extension through the gastric wall to the perigastric tissues, omenta, pancreas, colon, or liver.
Lymphatic drainage through numerous pathways leads to multiple nodal group involvement (e.g., intra-abdominal, supraclavicular) or seeding of peritoneal surfaces with metastatic nodules occurring on the ovary, ...