Stomach cancer


Stomach cancer, also known as gastric cancer, is a malignant tumor of the stomach. It is a cancer that develops in the lining of the stomach, caused by abnormal cell growth. Most cases of stomach cancers are gastric carcinomas, which can be divided into several subtypes, including gastric adenocarcinomas. Lymphomas and mesenchymal tumors may also develop in the stomach. Early symptoms may include heartburn, upper abdominal pain, nausea, and loss of appetite. Later signs and symptoms may include weight loss, yellowing of the skin and whites of the eyes, vomiting, difficulty swallowing, and blood in the stool, among others. The cancer may spread from the stomach to other parts of the body, particularly the liver, lungs, bones, lining of the abdomen, and lymph nodes.
The bacterium Helicobacter pylori accounts for more than 60% of cases of stomach cancer. Certain strains of H. pylori have greater risks than others. Smoking, dietary factors such as pickled vegetables and obesity are other risk factors. About 10% of cases run in families, and between 1% and 3% of cases are due to genetic syndromes inherited such as hereditary diffuse gastric cancer. Most of the time, stomach cancer develops in stages over the years. Diagnosis is usually by biopsy done during endoscopy. This is followed by medical imaging to determine if the cancer has spread to other parts of the body. Japan and South Korea, two countries that have high rates of the disease, screen for stomach cancer.
A Mediterranean diet lowers the risk of stomach cancer, as does not smoking. Tentative evidence indicates that treating H. pylori decreases the future risk. If stomach cancer is treated early, it can be cured. Treatments may include some combination of surgery, chemotherapy, radiation therapy, and targeted therapy. For certain subtypes of gastric cancer, cancer immunotherapy is an option as well. If treated late, palliative care may be advised. Some types of lymphoma can be cured by eliminating H. pylori. Outcomes are often poor, with a less than 10% five-year survival rate in the Western world for advanced cases. Most people with the condition present with advanced disease. In the United States, five-year survival is 37.9%, while in South Korea it is over 65% and Japan over 70%, partly due to screening efforts.
Globally, stomach cancer is the fifth-leading type of cancer and the third-leading cause of death from cancer, making up 7% of cases and 9% of deaths. In 2018, it newly occurred in 1.03 million people and caused 783,000 deaths. Before the 1930s, it was a leading cause of cancer deaths in the Western world; rates have sharply declined among younger generations in the West, although they remain high for people living in East Asia. The decline in the West is believed to be due to the decline of salted and pickled food consumption, as a result of the development of refrigeration as a method of preserving food. Stomach cancer occurs most commonly in East Asia, followed by Eastern Europe. It occurs twice as often in males as in females.

Signs and symptoms

Stomach cancer is often either asymptomatic or it may cause only nonspecific symptoms in its early stages. By the time symptoms are recognized, the cancer has often reached an advanced stage and may have metastasized, which is one of the main reasons for its relatively poor prognosis. Stomach cancer can cause the following signs and symptoms: Unexplained nausea, vomiting, diarrhoea, and constipation. Patients can also experience unexplained weight loss.
Early cancers may be associated with indigestion or a burning sensation. However, fewer than one in every 50 people referred for endoscopy due to indigestion has cancer. Abdominal discomfort and loss of appetite can occur.
Gastric cancers that have enlarged and invaded normal tissue can cause weakness, fatigue, bloating of the stomach after meals, abdominal pain in the upper abdomen, nausea and occasional vomiting. Further enlargement may cause weight loss or bleeding with vomiting blood or having blood in the stool, the latter apparent as black discolouration and sometimes leading to anemia. Dysphagia suggests a tumour in the cardia or extension of the gastric tumour into the esophagus.
These can be symptoms of other problems such as a stomach virus, gastric ulcer, or tropical sprue.

Risk factors

Gastric cancer can occur as a result of many factors. It occurs twice as commonly in males as females. Estrogen may protect women against the development of this form of cancer.

Infections

Helicobacter pylori infection is an essential risk factor in 65–80% of gastric cancers, but only 2% of people with H. pylori infections develop stomach cancer. The mechanism by which H. pylori induces stomach cancer potentially involves chronic inflammation, the action of H. pylori virulence factors such as CagA, or an interaction between H. pylori infection and germline pathogenic variants in homologous-recombination genes. It was estimated that Epstein–Barr virus is responsible for 84,000 cases per year. AIDS is also associated with elevated risk.

Smoking

Smoking increases the risk of developing gastric cancer significantly, from a 40% increased risk for people who currently smoke to an 82% increase for people who smoke heavily. Gastric cancers due to smoking mostly occur in the upper part of the stomach near the esophagus.

Alcohol

Some studies show increased risk with alcohol consumption as well.

Diet

Dietary factors are not proven causes, and the association between stomach cancer and various foods and beverages is weak. Some foods including fried foods, smoked foods, salt and salt-rich foods, meat, processed meat, red meat, pickled vegetables, and brackens are associated with a higher risk of stomach cancer.
Fresh fruit and vegetable intake, citrus fruit intake, and antioxidant intake are associated with a lower risk of stomach cancer. A Mediterranean diet is associated with lower rates of stomach cancer, as is regular aspirin use.
Obesity is a physical risk factor that has been found to increase the risk of gastric adenocarcinoma by contributing to the development of gastroesophageal reflux disease. The exact mechanism by which obesity causes GERD is not completely known. Studies hypothesize that increased dietary fat, leading to increased pressure on the stomach and the lower esophageal sphincter, due to excess adipose tissue, could play a role, yet no statistically significant data have been collected. However, the risk of gastric cardia adenocarcinoma, with GERD present, has been found to increase more than two times for an obese person. There is a correlation between iodine deficiency and gastric cancer.

Genetics

About 10% of cases run in families, and between 1 and 3% of cases are due to genetic syndromes inherited such as hereditary diffuse gastric cancer.
A genetic risk factor for gastric cancer is a genetic defect of the CDH1 gene known as hereditary diffuse gastric cancer. The CDH1 gene, which codes for E-cadherin, lies on the 16th chromosome. When the gene experiences a particular mutation, gastric cancer develops through a mechanism that is not fully understood. This mutation is considered autosomal dominant, meaning that half of a carrier's children will likely experience the same mutation. Diagnosis of hereditary diffuse gastric cancer usually takes place when at least two cases involving a family member, such as a parent or grandparent, are diagnosed, with at least one diagnosed before the age of 50. The diagnosis can also be made if at least three cases occur in the family, in which case age is not considered.
The International Cancer Genome Consortium is leading efforts to identify genomic changes involved in stomach cancer. A very small percentage of diffuse-type gastric cancers arise from an inherited abnormal CDH1 gene. Genetic testing and treatment options are available for families at risk.

Bile reflux

, in addition to Helicobacter pylori infection, is a pathogenic factor in gastric intestinal metaplasia, a precancerous lesion of gastric cancer. Long-term irritation of the gastric mucosa caused by bile reflux appears to have a role in gastric carcinogenesis. Bile acids, which are a significant component of bile reflux, may be a causal factor in gastric carcinogenesis.

Diagnosis

To find the cause of symptoms, the doctor asks about the patient's medical history, does a physical examination, and may order laboratory studies.
The patient may also have one or all of these exams:
In 2013, Chinese and Israeli scientists reported a successful pilot study of a breathalyzer-style breath test intended to diagnose stomach cancer by analyzing exhaled chemicals without the need for an intrusive endoscopy. A larger-scale clinical trial of this technology was completed in 2014.
Abnormal tissue seen in a gastroscope examination is biopsied by the surgeon or gastroenterologist. This tissue is then sent to a pathologist for histological examination under a microscope to check for the presence of cancerous cells. A biopsy, with subsequent histological analysis, is the only sure way to confirm the presence of cancer cells.
Various gastroscopic modalities have been developed to increase the yield of detected mucosa with a dye that accentuates the cell structure and can identify areas of dysplasia. Endocytoscopy involves ultra-high magnification to visualise cellular structure to better determine areas of dysplasia. Other gastroscopic modalities such as optical coherence tomography are being tested investigatively for similar applications.
Several skin conditions are associated with gastric cancer. A condition of darkened hyperplasia of the skin, frequently of the axilla and groin, known as acanthosis nigricans, is associated with intra-abdominal cancers such as gastric cancer. Other cutaneous manifestations of gastric cancer include "tripe palms" and the Leser-Trelat sign, which is the rapid development of skin lesions known as seborrheic keratoses.
Various blood tests may be done, including a complete blood count to check for anaemia, and a fecal occult blood test to check for blood in the stool.