The National Cancer Institute, one of the National Institutes of Health, periodically produces a statement of importance to the public and to health providers. You can read both statements on cancer prevention here. This month’s column is based on the information about preventing cancer from their report.
Cancer is a disease that, as we age, we become more likely to develop; yet age is not a risk factor per se. The Centers for Disease Control and Prevention (CDC) estimates that this year 1.7 million people will be diagnosed with a new cancer and about a third of that number (roughly 600 thousand) will die from cancer in 2016. There are many specific risk factors and, for the purposes of this column, we will discuss mostly the ones that we can change. We cannot, for example, change our gender, age, and genes – all of which affect cancer risk.
Cancer tends to strike fear into people because it is the second (to heart disease) leading cause of death in this country. It also inflicts enormous stress on patients with it and on the family involved in the care of a loved one with it. Needless to say, there is often a reduction in quality of life and even financial well-being in patients with cancer.
Cancer Risk Factors – Where Do They Come From?
Table 1 (below) lists factors that are confidently associated with various cancers. Avoidance of the risk factors puts us in a safer category in relation to cancer (and other diseases in many cases.) Table 2 lists factors that may be associated with certain cancers.
Smoking is thought to be directly related to 30 percent of cancer in the United States. Some of the cancers linked to smoking are lung, bladder, esophageal, mouth, kidney, pancreas, stomach, and leukemia. It is also known that not smoking, but being around a smoker – so called “second hand smoking” – also leads to these cancers. Smoking is the greatest preventable risk factor for cancer. Stopping smoking or reducing second-hand exposure to it can reduce risk.
Infection with a virus or some bacteria causes cancer. The human papilloma virus (HPV) causes cancer of the cervix, penis, vagina, anus, and oropharynx. Sexual transmission is common. There is now a vaccine to prevent HPV transmission. Hepatitis B and hepatitis C are viral diseases that can lead to primary liver cancer. Fortunately there is also a vaccine to prevent hepatitis B transmission. The helicobacter pyloriorganism increases risk of stomach cancer. This bacterium is very common and occurs more as we age. It is also associated with ulcers and can be treated with antibiotics, but if it is untreated, cancer can develop.
Radiation is another known cause of cancer. Ultraviolet radiation from exposure to the sun causes non-melanoma skin cancers. Ionizing radiation from medical tests and nuclear exposures causes leukemia, thyroid, and breast cancer and is suspected to contribute to myeloma, lung, stomach, colon, esophageal, bladder, and ovarian cancers.
Immunosuppression drugs are used in transplant patients and some other patients with autoimmune diseases. The immunosuppression drugs inhibit the body’s normal immune system that fights cancer. If one’s immune system is inhibited lymphoma, lung, kidney, and liver cancer risk is increased. This is a classic case where the delicate balance between the benefit of the drugs and the risk of causing harm must be weighed before taking immunosuppression drugs that are often life-saving.
General Factors Associated with Some Cancers
- Cigarette smoking and tobacco use
- Immunosuppressive medicines
Factors with Possible Association to Cancer
- Alcohol consumption
- Physical activity (inactivity)
- Environmental factors
Cancer Risk Factors – Probable Ones
The evidence is less compelling about risk factors shown in Table 2. Because so many of the factors in this table are intertwined, it is hard to be certain that each variable alone causes cancer. What is known is that these factors are generally found in patients with certain types of cancer.
Diet is probably the most complex of risk factors. People have to eat so all people – well and those with cancer – are on a diet, and the diets (meaning what people eat) are not very different across large groups of people. Eating fruit is thought to protect against cancer of the mouth, esophagus, stomach, and possibly lung cancers. Diets low in fat and high in fiber, fruits, and vegetables are thought to be preventive of colon cancer. Diets high in fat, protein, calories, and red meat are thought to predispose to colon cancer. There is not enough data to support the taking of any minerals, vitamins, multi-vitamins, and other supplements as preventive therapy for cancer.
Alcohol consumption has been linked to some cancers such as mouth, esophageal, breast, and colon. It is also believed that excessive alcohol consumption leads to cancer of the liver (along with other liver pathology).
Exercise has been shown to lower the risk of colon cancer and some evidence exists to support the preventive influence of physical activity on postmenopausal breast cancer and endometrial cancer in women.
Obesity is related to diet and exercise, of course, but also to the development of certain cancers such as postmenopausal breast, colon, endometrial, esophageal, kidney, and pancreatic cancer.
Diabetes seems to slightly increase the risk of bladder, breast, colon, endometrial, liver, mouth, ovarian, and pancreatic cancers. Of course, diabetes also tends to coexist with older age, obesity, diet, exercise, and the other factors mentioned in Table 2, so it is difficult to be sure if it is one or all factors that add to the risk.
Environmental factors such as certain chemicals and polluted air carry cancer risks. Asbestos, for example, is a known cancer risk and arsenic found in water can cause skin, bladder, and lung cancer. Certain pesticides are also carcinogens (substances that cause cancer). We have already mentioned second hand smoking as a risk for lung cancer.
The Bottom Line
There are many factors that we cannot control that predispose us to developing cancer, like age, gender, and family history (genetics). However, there are a great many factors that we do have some control over that are known risk factors for cancer. It is our responsibility to use this information to help us try and avoid cancer as we age.