cancer nutrition

Lifestyle and Cancer

Nutrition

The relationship between food intake and cancer is complex and not well understood. Research seems to indicate that certain foods may have either protective or promoting effects on the development of cancer. Foods that have a protective effect seem to play a role in the prevention of certain types of cancers. Foods that have promoting effects are associated with an increased risk of developing certain types of cancers. According to the American Cancer Society, the single most important dietary intervention to lower risk for cancer is eating five or more servings of fruits and vegetables daily. Adopting a diet rich in plant sources provides phytochemicals that possess health protective benefits. Dietary recommendations related to reducing risk of cancer include the recommendation to choose most foods from plant sources such as fruits and vegetables. Five or more servings of fruits and vegetables should be consumed every day. Fruits and vegetables should be eaten at every meal and as snacks. Other foods from plant sources that should be included in the diet several times a day include breads, cereals, grain products (preferably whole grain), rice, and pasta. Beans should be eaten as an alternative to meat. The foods and herbs with the highest anticancer activity include garlic, soybeans, cabbage, ginger, licorice root, and the umbelliferous vegetables such as carrots. Citrus foods also contain a host of active phytochemicals.

A diet rich in foods from plant sources may reduce the risk for development of cancers of the gastrointestinal tract, respiratory tract, and colon. Vegetables that seem to play a strong role in protecting against colon cancer include green and dark yellow vegetables, vegetables in the cabbage family, soy products, and legumes. Increased consumption of fruits and vegetables reduce risk for lung cancer, even for those individuals who smoke. Forms of fruits and vegetables that appear to provide the greatest protection include foods in fresh, frozen, canned, dried, or juice forms. Extractions from fruits and vegetable do not provide protective effects.

Diets high in fat have been associated with some increased risk for colon, rectal, prostate, and endometrial (uterine) cancers. The association between high-fat diets and the development of breast cancer is much weaker. Specific dietary recommendations are to replace high-fat foods with fruits and vegetables, eat smaller portions of high-fat foods, and limit consumption of meats, especially those that are considered high in fat.

Foods from animal sources remain a staple in American diets. Consumption of meat, especially red meats such as beef, pork, and lamb, have been associated with increased risk of colon and prostate cancer. Cooking methods also have been linked to the development of cancer. Mutagenic compounds are produced when proteins such as meat protein are cooked at high temperatures. These compounds may be responsible for the association between meat consumption and increased risk for colon cancer.

Obesity has been linked to cancers at several sites including colon and rectum, prostate, and kidney, as well as endometrial and breast cancer in postmenopausal women.

Physical Activity

Recommendations related to physical exercise include engaging in moderate levels of activity for at least 30 minutes most days of the week. Studies have revealed an association between physical activity and a reduced risk of the development of certain types of cancers, including colon, breast, and prostate cancer. For example, physical activity is thought to stimulate the movement of stool through the bowel, resulting in less exposure of the bowel lining to mutagens in the stool.

Consumption of Alcohol

Drinking alcohol has been linked to increased risk of developing cancers of the mouth, esophagus, pharynx, larynx, and liver in both men and women, and increases the risk of breast cancer in women. Cancer risk increases as the amount of alcohol consumed increases. An individual who both smokes and drinks alcohol greatly increases the risk of developing cancer when compared to either smoking or drinking alone. Risk increases significantly for cancers of the mouth, esophagus, and larynx when more than two drinks per day are consumed. A drink is defined as 5 ounces (141.75 grams) of wine, 12 ounces (340.20 grams) of regular beer, or 1.5 ounces (42.52 grams) of 80-proof distilled spirits. Women who drink are at increased risk for the development of breast cancer. Studies have shown that the risk of breast cancer increases with just a few drinks per week.

Consumption of Tobacco

Smoking-related illnesses account for more than 400,000 deaths each year in the United States. These deaths occur 12 years earlier than would be expected on average. Tobacco is known as one of the most potent human carcinogens. Tobacco causes more than 148,000 deaths each year in the form of various cancers. Most of the cancers of the lung, trachea, bronchus, larynx, pharynx, oral cavity, and esophagus diagnosed each year are caused by tobacco. Smoking is also associated with cancers of the pancreas, kidney, bladder, and cervix. Smoking is known to affect the health of nonsmokers through environmental or secondhand smoke, which is implicated in causing lung cancer. Cigarette smoking is more common among men; however, because of the increase in the number of women who smoke, more women die from lung cancer each year than from breast cancer. Mortality from lung cancer for men appears to have peaked and has been declining since the 1980s. This decline in mortality is attributed to a decrease in tobacco product use among men.

Substantial health benefits occur once an individual stops smoking. If a smoker stops smoking before the age of 50 years, his or her risk of dying in the next 15 years is half of that for a continuing smoker. Even if the smoker stops smoking after the age of 70 years, the risk of dying is still reduced substantially. After 10 years of not smoking, an ex-smoker's risk of lung cancer is reduced by 30%–50%. After five years of not smoking, an exsmoker's risk of oral and esophageal cancer is reduced by 50%. Risk for cervical and bladder cancer is also reduced once smoking is stopped.

The three treatment elements identified as particularly effective in smoking cessation treatment include pharmacotherapy, such as nicotine replacement patches and gums, social support from physicians and other clinicians, and skills training and problem solving, particularly in the areas of smoking cessation and abstinence techniques.

Radiation Exposure

Only high-frequency radiation such as ionizing radiation (IR) and ultraviolet (UV) radiation has been proven to cause cancer in humans. A source of ultraviolet radiation is sunlight. Prolonged, unprotected exposure to UV radiation is the major cause of basal and squamous cell skin cancers. UV radiation is also a major cause of melanoma. Disruption of the earth's ozone layer by pollution is thought to result in increasing levels of UV radiation reaching the earth's surface, which has been linked to the rise in the incidence of skin cancers and melanomas.

IR has cancer-causing capability as proven by studies on atomic bomb survivors and other groups. Virtually any part of the body can be affected by IR, but the areas most affected are the bone marrow and the thyroid gland. IR is released in very low levels from diagnostic equipment such as medical and dental X-ray equipment. Much higher levels of IR are released from machines delivering radiation therapy. Great precautions are taken during treatment not to expose patients or staff unnecessarily to the effects of IR. Another occupational group affected by IR includes uranium miners. Exposure to radon, a naturally occurring gas which is a form of IR, can increase risk for lung cancer, especially among smokers.

cancer prevention

Cancer Prevention

Definition

Preventing the incidence of cancer is complex and involves many factors that ultimately work by avoiding or limiting exposure to carcinogens. Known carcinogens in humans include physical, chemical, viral, and bacterial carcinogens. Physical carcinogens include the hydrocarbon byproducts of cigarette smoke, radiation, and asbestos. Benzene and vinyl chloride are examples of chemical carcinogens. The human papillomaviruses, which play a role in the development of cervical cancer, are viral carcinogens. A bacterial carcinogen is the bacteria, Helicobacter pylori, which has been linked to the cancer B-cell lymphoma, unique to the gastric mucosa. Familial (hereditary) carcinogenesis plays a role in as many as 15% of all human cancers and has been implicated as the cause of some cases of melanoma, breast, colon, and other cancers.

Some factors that place individuals at high risk for the development of cancer can be modified to decrease risk for development. For example, people can make lifestyle and environmental changes to decrease risk. Behavior modification such as dietary changes, exercise, and avoiding exposure to known carcinogens are primary prevention measures that everyone should adopt.

An evolving field, chemoprevention, is the use of vitamins or medicines to prevent cancer development. In 2003, the U.S. Preventive Services Task Force released a report stating that evidence was insufficient to recommend for or against use of vitamin supplements to help prevent cancer. The task force recommended against supplementation with beta carotene because of higher incidence of lung cancer among those who used certain levels of beta carotene supplements.

Chemopreventive agents have the ability to potentially delay and even reverse the sequence of events at the cellular level that change a normal cell to a cancer cell. An example of a chemopreventive agent is tamoxifen, a drug that is effective in preventing breast cancer in women who are at high risk for developing breast cancer. Vaccines for Hepatitis B virus will not only prevent primary Hepatitis B and liver failure, but also liver cancer.

Preventive surgery may be an option for those individuals who are considered to be at high risk of developing cancer because of a genetic or inherited predisposition. Examples of preventive surgery are prophylactic (preventive) mastectomy to reduce risk for breast cancer, and colon polyp removal in individuals at high risk for the development of colon cancer.

In 2003 the American Cancer Society (ACS) estimated that 30,000 cancer deaths were caused by cigarette smoking alone and some 180,000 deaths could be attributed to tobacco use. All cancers caused by smoking cigarettes and by excessive use of alcohol can be completely prevented. Alcohol consumption is another risk factor for cancer. According to the ACS, up to one-third of the more than 555,000 cancer deaths in the United States in 2003 were related to poor nutrition or insufficient physical exercise. A 2003 study reported that women of average weight who walked briskly at least 1 and one-fourth hours per week had a 30% lower risk of breast cancer than women who did not exercise. Many of the more than one million skin cancers that develop annually could be prevented by adopting protective measures from ultraviolet radiation caused by the sun.

Different cancers are associated with different risk factors. While modification of risk factors plays an important role in the prevention of cancer, it is known that some individuals who have one or more risk factors never develop cancer. Others, however, who have no known risk factors, are eventually diagnosed with cancer. Research aimed at identifying additional risk factors for specific cancers continues.

deep brain stimulation

Deep brain stimulation

Definition

In deep brain stimulation (DBS), electrodes are implanted within the brain to deliver a continuous low electric current to the target area. The current is passed to the electrodes through a wire running under the scalp and skin to a battery-powered pulse generator implanted in the chest wall.

Purpose

DBS is used to treat Parkinson's disease (PD) and essential tremor (ET). It has also been used to treat dystonia, chronic pain, and several other conditions.

The movement disorders of PD and ET are due to loss of regulation in complex circuits within the brain that control movement. While the cause of the two diseases differs, in both cases, certain parts of the brain become overactive. Surgical treatment can include destruction of part of the overactive portion, thus rebalancing the regulation within the circuit. It was discovered that the same effect could be obtained by electrically stimulating the same areas, which is presumed to shut down the cells without killing them.

DBS may be appropriate for patients with PD or ET whose symptoms are not adequately controlled by medications. In PD, this may occur after five to ten years of successful treatment. Continued disease progression leads to decreased effectiveness of the main treatment for PD, levodopa. Increasing doses are needed to control symptoms, and over time, this leads to development of unwanted movements, or dyskinesias. Successful DBS allows a reduction in levodopa, diminishing dyskinesias.

For PD, deep brain stimulation is performed on either the globus pallidus internus (GPi) or the subthalamic nucleus (STN). Treatment of essential tremor usually targets the thalamus. Each of these brain regions has two halves, which control movement on the opposite side of the body: right controls left, and left controls right. Unilateral (onesided) DBS may be used if the symptoms are much more severe on one side. Bilateral DBS is used to treat symptoms on both sides.

Precautions

DBS is major brain surgery. Bleeding is a risk, and patients with bleeding disorders or who are taking blood thinning agents may require special management. DBS leaves metal electrodes implanted in the head, and patients are advised not to undergo diathermy (tissue heating) due to the risk of severe complications or death. Diathermy is used to treat chronic pain and other conditions. Special cautions are required for patients undergoing MRI after implantation.

Description

In DBS, a long thin electrode is planted deep within the brain, through a hole in the top of the skull. To make sure the electrode is planted in the proper location, a rigid "stereotactic frame" is attached to the patient's head before surgery. This device provides a three-dimensional coordinate system, used to locate the target tissue and to track the placing of the electrodes.

A single "burr hole" is made in the top of the skull for a unilateral procedure. Two holes are made for a bilateral procedure. This requires a topical anesthetic. General anesthesia is not used, for two reasons. First, the brain does not feel any pain. Second, the patient must be awake and responsive in order to respond to the neurosurgical team as they monitor the placement of the electrode. The target structures are close to several nerve tracts that carry information throughout the brain. Abnormalities in vision, speech, or other cognitive areas may indicate that the electrode is too close to one of these regions, and thus needs repositioning.

Other procedures may be used to ensure precise placement of the electrode, including electrical recording and injection of a contrast dye into the spinal fluid. The electrical recording can cause some minor odd sensations, but is harmless.

The electrode is connected by a wire to an implanted pulse generator. This wire is placed under the scalp and skin. A small incision is made in the area of the collarbone, and the pulse generator is placed there. This portion of the procedure is performed under general anesthesia.

Preparation

A variety of medical tests are needed before the day of surgery to properly locate the target (GPi, thalamus, or STN), and fit the frame. These may include CT scans, MRI, and injection of dyes into the spinal fluid or ventricles of the brain. The frame is attached to the head on the day of surgery, which may be somewhat painful, although the pain is lessened by local anesthetic. A mild sedative is given to ease anxiety.

Aftercare

Implantation of the electrodes, wire, and pulse generator is a lengthy procedure, and the patient will require a short hospital stay afterward to recovery from the surgery. Following this, the patient will meet several times with the neurologist to adjust the stimulator settings, in order to get maximum symptomatic improvement. The batteries in the pulse generator must be replaced every three to five years. This is done with a small incision as an outpatient procedure.

The patient's medications are adjusted after surgery. Most PD patients will need less levodopa after surgery, especially those who receive DBS of the STN.

Risks

Risks from DBS include the surgical risks or hemorrhage and infection, as well as the risks of general anesthesia. Patients who are cognitively impaired may become more so after surgery. Electrodes can be placed too close to other brain regions, which can lead to visual defects, speech problems, and other complications. If these occur, they may be partially reduced by adjusting the stimulation settings. DBS leaves significant hardware in place under the skin, which can malfunction or break, requiring removal or replacement.

Normal results

Deep brain stimulation improves the movement symptoms of PD by 25–75%, depending on how carefully the electrodes are placed in the optimal target area, and how effectively the settings can be adjusted. These improvements are seen most while off levodopa; DBS does little to improve the best response to levodopa treatment. DBS does allow a reduction in levodopa dose, which usually reduces dyskinesias by 50% or more. This is especially true for DBS of the STN; DBS of the GPi may lead to a smaller reduction. Levodopa dose will likely be reduced, leading to a significant reduction in dyskinesias.

DBS in essential tremor may reduce tremor in the side opposite the electrode by up to 80%.

bipolar

ddddddddddddd