Causes And Mechanism Of Gastric Cancer Biology Essay


Stomach cancer, or gastric cancer, is the uncontrolled growth arising from any part of the stomach. Gastric cancer is a cause of substantial morbidity and mortality. According to global database, gastric cancer is the fourth most common cancer, with an incidence that varies greatly across different geographic locations. Gastric cancer is the most common gastrointestinal malignancy after colorectal and pancreatic cancer. In spite of the decreasing worldwide incidence, gastric cancer accounts for 3% to 10% of all cancer-related deaths.

The stomach is an expanded part of the digestive tube that lies beneath the ribs. It receives the softened food from the esophagus. Mixing and partial digestion of the food is carried out in the stomach with the help of its gastric secretions and food is converted into a pulpy fluid which then passes into the small intestine for further digestion and absorption. Stomach consists of 5 layers, lining cells and glands secrete enzymes, muscular layer helps in food digestion and outermost layer gives protection.

Causes and Risk factors

Causes and mechanism of gastric cancer

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Chronic gastritis associated with H. pylori infection is the major cause of stomach cancer. Gastritis is generally accompanied by loss of gastric cells and structure. The mechanisms of malignant transformation are not entirely clear. Chronic inflammation induced by H. pylori may release toxic substances, which eventually cause DNA damage.

Whatever the cause is the basic mechanism of cancerous growth is the same. Cancer is an uncontrolled growth and it starts with an error in the DNA. This error is called mutation. DNA is the genetic material of cell. When mutation occurs it causes cell to grow and divide at a very rapid rate that is uncontrolled. Rapidly growing cancer cells compromise the blood supply of normal cells, as a result normal cells die. These cancer cells accumulate to form a lump and can penetrate the surrounding tissues. The cancer cells can move through blood and other medium and spread throughout the body.

Among the cancers that occur in the stomach, adenocarcinoma is tremendously the most important and the most common (90% to 95%). Next in order of frequency are lymphomas (4%), carcinoids (3%), and stromal tumors (2%).

Types of gastric cancer

Stomach cancer is of following types;

Gastric adenocarcinoma

Gastric adenocarcinoma is of two types, called intestinal and diffuse. The intestinal type is characterized by expansile or ulcerative growth and arises from gastric mucous cells. Intestinal type of adenocarcinoma is associated with chronic gastritis caused by H. pylori infection. This pattern of cancer tends to have good prognosis. In contrast, the diffuse type exhibits inward and diffuse growth pattern and it has poor prognosis. The cause of diffuse type carcinoma is unknown. Whereas the intestinal-type carcinoma occurs primarily after age 50 years with a 2 : 1 male predominance, the diffuse carcinoma occurs at an earlier age with female predominance.

Carcinoid tumors

These tumors arises from hormone producing cells of stomach.The peak incidence of these neoplasms is in the sixth decade, but they may appear at any age.

Gastric MALT lymphomas

These tumors arise from immune cells, as a result of Helicobacter-associated chronic gastritis. Lymphomas arising from stomach generally have a better prognosis. This type of gastrointestinal lymphoma usually affects adults, lacks a sex predilection.


GIST occurs most commonly in the stomach. GIST occurs uniformly across all geographic and ethnic groups, and affects men and women equally. It is predominantly seen in patients >40 years old and is only rarely reported in children.

Risk factors

Several major variables are thought to affect the growth of this form of cancer. Few risk factors of stomach cancer are as follow;

Chronic gastritis

Helicobacter pylori infection

Nitrites are derived from nitrates which are found in food and drinking water, and used as preservatives in prepared meats.

Diets containing smoked foods, pickled vegetables and excessive salt intake.

Partial gastrectomy

Pernicious anemia

Gastric polyps are small elevations from stomach inner lining.

Decreased intake of fresh vegetables and fruits


Food contaminated with aflatoxin fungus

Family history of stomach cancer

Being older or male

Eating foods that have not been prepared or stored properly


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The complications that can be experienced by patients of stomach cancer may include;


When tumor mass blocks the food passage it results in decrease absorption of food.


Malabsorption leads to loss of essential nutrients

Bowel obstruction

Tumor mass causes obstruction to food which results in vomiting.

Gastrointestinal bleeding

This comprises of vomiting blood or passing blood through stool.

Weight loss


Stomach can spread throughout the body and this process is called metastasis.


Advanced stomach cancer will severely affect digestion and nutrition and may spread to other parts of the body, finally causing death.

Pharmaceutical therapies

The treatment therapy for stomach cancer depends on the stage of the cancer and health of the patient.


Surgery to remove the stomach (gastrectomy) is the only treatment that can cure the condition. When the cancer is at stage 1 the doctors most likely use surgery to treat the cancer. Surgical options include;

Laparoscopy: A small incision to push a tube with camera inside your stomach to understand the location of the cancer is and to decide for the subsequent surgery.

Partial Gastrectomy: Remove a part of the stomach

Total Gastrectomy: Remove all of the stomach. This may even include surrounding area such as oesophagus, intestine or the spleen depending upon the spread of tumour.

Remove some or all of the lymph nodes

Create a bypass from the esophagus straight to the intestine

Endoscopic Laser surgery

Gastrectomy is major surgery. For a certain period of time after the surgery, the person's activities are restricted to allow healing to take place. After surgery patient is fed intravenously (through a vein) and after few days, patients are ready for liquids and then solid, foods. Those who have had their complete stomach removed cannot absorb vitamin B12, which is essential for healthy blood and nerves, so they get regular injections of vitamin B12. Patients may also need to change their diet. The doctor or a dietitian (a nutrition specialist) will describe any required dietary changes.

After surgery many patients experience cramps, nausea, diarrhea, and dizziness shortly after eating because food and liquid directly enter the small intestine. These symptoms can be treated by changing the patient's diet. Patient is advised to eat several small meals throughout the day and to avoid foods that contain sugar. The symptoms usually disappear in 3 to 12 months, but they may be permanent.

For patients who cannot have surgery, chemotherapy or radiation can improve symptoms and may prolong survival, but will likely not cure the cancer. For some patients, a surgical bypass procedure may relieve symptoms.


Radiotherapy is rarely used in the treatment of stomach cancer because it damages the surrounding organs like the liver. The main purpose of it use is to stop bleeding, reduce pain or to shrink a tumor when it is blocking the stomach passage.

For some people, radiation therapy causes minimal no side effects. For others, the side effects can very severe. The side effects of radiation therapy differ according to type and location of cancer, treatment plan, and the patient's general health. Side effects to radiotherapy include infections, nausea, vomiting, and diarrhea. The doctor can prescribe medicine or recommend dietary changes to relieve these symptoms. The skin in the treated area may become red, dry, painful to touch, and itchy. Patients should not wear those clothes that can rub; loose cotton clothes are generally best.


Chemotherapy is used only when the stomach cancer is difficult to operate; or when the cancer is stage 3 or 4 and has started to spread throughout the body. It may be used before surgery to reduce the size of the tumor, or after surgery to reduce the risk of cancer coming back after surgery. It may also be used to try to slow down the cancer and improve quality of life if an operation to remove the cancer isn't possible.

Chemotherapy can be taken as tablets, or given into a vein (intravenously) by means of injections or drips (infusions).The most common drugs used are Cisplatin, Taxol, Epirubicin, Fluorouracil, Lomustine, Mitomycin and Methotrexate. Capecitabine and oxaliplatin are the new drugs using now-a-days.

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Chemotherapy can cause many side effects, but these can generally be controlled with medicines. The main side effects are lowered resistance to infections, feeling sick, diarrhea, nausea, vomiting, sore mouth, sore hands and feet, anemia, bruising, bleeding, hair loss, tiredness, numbness in hands and feet etc. These effects usually go away slowly after the stomach cancer treatments stop or during the recovery period between treatments.

Biological Immune Therapies

This is a new range of therapy. In this monoclonal antibodies or vaccines, which are prepared from the cancer cells, are injected in patient's body to increase immune response to fight against cancer.

Treatment plan according to stage of stomach cancer

Stage 0 (Carcinoma in Situ)

Treatment of stage 0 is usually surgery (total or subtotal gastrectomy).

Stage I

Treatment of stage I gastric cancer includes the following:

Surgery (total or subtotal gastrectomy).

Surgery (total or subtotal gastrectomy) followed by chemotherapy and radiationtherapy.

A clinical trial of chemotherapy and radiationtherapy is also given before surgery.

Stage II

Treatment of stage II gastric cancer includes the following:

Surgery (total or subtotal gastrectomy).

Surgery (total or subtotal gastrectomy) followed by chemotherapy and radiationtherapy or just chemotherapy.

Chemotherapy given before and after surgery.

Stage III

Treatment of stage III gastric cancer includes the following:

Surgery (total gastrectomy).

Surgery followed by chemoradiation therapy or chemotherapy.

Chemotherapy given before and after surgery

Stage IV and Recurrent stomach Cancer

Treatment of stage IV or recurrent stomach cancer includes the following:

Chemotherapy to relieve symptoms and to improve the quality of life

Therapy with a monoclonal antibody combined with chemotherapy.

Laser therapy or stent placement to relieve a blockage in the stomach

Radiation therapy to stop bleeding, to relieve pain, or to shrink a tumor that is blocking the stomach

Surgery to stop bleeding or shrink a tumor that is blocking the stomach

Lifestyle factors, Support and Prevention

We are not sure about what causes stomach cancer, so there's no approach to prevent it. But you can take few steps to reduce your risk of stomach cancer by making minor changes to your everyday life. The following may help reduce your risk of gastric cancer and improve lifestyle:

Don't smoke

Eat a healthy, balanced diet rich in fruits and vegetables

Don't take salty and smoked foods.

Take herbs and other foods that don't add sodium.

Take a medication to treat stomach disease

Eradication of H. pylori infection at early stage

Mass screening programs have been effective at identifying disease in the early stages. Consider regular endoscopy to look for stomach cancer

The Cabbage Diet alkalizes the body and maintains a normal pH in stomach. The cabbage is also anti-inflammatory and it helps in digestion. Cabbage can kill off the foreign and causal bacteria of stomach.


After being diagnosed with stomach, try to learn about stomach cancer. Ask your doctor about the details of your cancer including its type, stage and treatment options. Converse your preferences and concerns about treatments with your doctor.

You can comfort the stress of illness by joining a support group with supporters who share common problems and experiences.

Eating healthy and getting enough rest can help fight against the stress and fatigue of cancer. Stay active. If you are diagnosed with cancer it doesn't mean you have to end doing the things you enjoy or usually do.

Natural treatment

Aloe vera

Aloe vera is a medicinal plan. Aloe vera appears to prove useful in the treatment of stomach cancer. It kills H. pylori bacteria. About 90% of individuals with gastric cancer have H. pylori bacteria in the stomach. It also inhibits acid secretion from the stomach. Excess acid production causes gastritis. H. Pylori bacteria encourage inflammation in the stomach. Aloe vera inhibits inflammation in several different ways. Some of the chemicals found in aloe may have helpful effects on the immune system and can shrink some cancers. Studies show that patients taking the aloe vera with chemotherapy had a better quality of life and that they had fewer chemotherapy side effects such as numb fingers and fatigue. There are no ill effects from the aloe vera. Patients who take the aloe vera have 3 years survival rate than patients who just have chemotherapy.

Black cumin

Black cumin seeds have been used for centuries to treat a variety of diseases. It's scientific name is "Nigella sativa," The crude oil and thymoquinone (TQ) extracted from its seeds and oil are effective against many diseases like cancer, cardiovascular complications, diabetes, asthma, kidney disease etc. Research suggests that the black seed is an effective anti-tumor treatment for stomach cancer. Black cumin, have been tested in the lab and found to have powerful antioxidant and anti-cancer effects. Antioxidants are chemicals that cleared the body of free radicals that cause cell damage and stimulate disease. The oil, extract or TQ component can kill cancer cells and protect healthy tissues during treatment.


Curcumin (diferuloylmethane) is a polyphenol derived from the plant Curcuma longa, generally called turmeric. Extensive research over the last 50 years has indicated this polyphenol can both prevent and treat cancer. Several studies recommend that curcumin has massive potential in the prevention and therapy of stomach cancer. It inhibits growth and production of human gastric cancer and is mainly effective in stopping cancers that have become resistant to chemotherapy. Infection with the bacterium Helicobacter pylori (H. pylori) is a known cause gastric cancer. Curcumin blocks growth of H. pylori and reduces the rate at which stomach cells react to infection by turning into cancer cells. Curcumin is found to be safe and has no side effects.


Epigallocatechin gallate, or EGCG, is an antioxidant present in tea. Tea is one of the most widely consumed beverages, second only to water. The cancer-protective effects of green tea have been reported in several studies. Cancer rates are low in countries such as Japan where green tea is consumed on a regular basis. Several animal and clinical studies propose that EGCG play an important role in the prevention of stomach cancer. It has been suggested that EGCG and other tea catechins suppress tumor progression by inhibiting the release of tumor factors. The exposure of human stomach cells to EGCG led to both growth inhibition and the stimulation of programmed cell death (apoptosis). EGCG have been shown to prevent DNA damage caused by free radicals. DNA damage can cause cells to malfunction and lead to a number of health issues including cancer. Studies involving large populations of people suggest that drinking green tea may be associated with a lower risk of some cancer types.


Quercetin is a plant-based chemical and also known as a flavonoid. Quercetin is a dietary antioxidant and found in many plants and foods. It is an important component of berries, red wine, onions, buckwheat, tea green tea and apples. Quercetin is used as a medicine and it also has anti-proliferative activities against gastric cancer. Quercetin is a promising cancer chemopreventive agent that inhibits tumor promotion by inducing cell cycle arrest and promoting cell death. Quercetin appears to have with little toxicity when administered orally or intravenously.


Resveratrol is a naturally occurring polyphenol with potent anticancer activity. It has since been found in various plants, including grapes, berries and peanuts. Studies suggested that resveratrol induces tumor cell death via reactive oxygen species. Resveratrol inhibit proliferation of a number of cell lines and exhibits anticancer properties, by its ability to suppress proliferation of a wide variety of tumor cells, including lymphoma, melanoma, multiple myeloma, squamous cell carcinoma, cancers of the prostate, breast, stomach, ovary, cervix, colon, pancreas, and thyroid. Resveratrol might produce anticancer effects by its antioxidant action. It stimulates NOS to produce low levels of NO, which, in turn, exert antioxidant action. Consumption of a resveratrolrich diet is advised because of its protective role against gastric cancer. Limited data in humans have revealed that resveratrol is pharmacologically quite safe.

There are a number of vitamins and supplements that may help in stomach cancer and enhance the immune system. Research suggested that vitamin D, fish oils and natural vitamins like vitamin E has anticancer effect in Gastro-intestinal cancers.