The term “cancer” encompasses a group of diseases characterized by the uncontrolled multiplication and spread of abnormal cells. If the cancer cells are not eliminated, the progression of the disease will sooner or later lead to the death of the affected person.
Cancer can be due to external factors (lifestyle, environmental or occupational factors, infections), or internal (hereditary mutations, hormones, immune system disruption, etc.). These risk factors can act together or in succession, and trigger or promote the development of cancer. Often, it takes several tens of years between exposure to external factors and the onset of the disease.
There are more than 100 varieties of cancer, or malignant tumor, which can lodge in different tissues and organs.
Most cancers take several years to form. They can appear at any age, but they are more often found in people aged 60 and over.
Note. Benign tumors are not cancerous: they are unlikely to destroy nearby tissue and spread throughout the body. However, they can put pressure on an organ or tissue.
Causes of cancer
The body has an array of tools to fix genetic “mistakes” or outright destroy potentially cancerous cells. However, sometimes these tools are defective for one reason or another.
Several factors can accelerate or cause the emergence of cancer. In fact, it is most often believed that a combination of risk factors leads to cancer. Age is an important factor. But it is now accepted that about two thirds of cancer cases are attributable to lifestyle habits, mainly smoking and diet. Exposure to carcinogens in the environment (air pollution, toxic substances handled at work, pesticides, etc.) also increases the risk of cancer. Finally, hereditary factors are responsible for 5% to 15% of cases.
- In 2017 — according to the latest data available — 1,701,315 new cases of cancer were reported in the United States, and 599,099 died of cancer that same year.
- Breast cancer is the most common cancer among women in the United States. 12% of women will develop breast cancer in their lifetime.
- Prostate cancer is the most commonly diagnosed cancer among men. 207,430 cases were reported in 2017. In 97% of cases, the patients are 50 or older
Rate of new cases of cancer
Cancer around the world
The most common types of cancer vary from region to region of the world. In Asia, cancers of the stomach, esophagus and liver are much more common, especially because the diet of the inhabitants consists of a large part of very salty, smoked and pickled foods.
In sub-Saharan Africa, cancers of the liver and cervix are very common due to the hepatitis and human papillomavirus (HPV).
In North America as well as in Europe, cancers of the lung, colon, breast and prostate are the most common, among other things due to smoking, poor eating habits and obesity.
In Japan, the consumption of red meat, which has steadily increased over the past 50 years, has increased the incidence of colon cancer by 7 times. Emigrants generally end up having the same illnesses as the population of their host country.
No doctor can predict with certainty the course of cancer or the chances of survival for a particular person. Statistics regarding survival rates do, however, give some idea of how the disease progresses in a large group of people.
A large proportion of patients recover definitively from cancer. According to a large survey carried out in France, more than 1 in 2 patients are still alive 5 years after being diagnosed.
The cure rate depends on a multitude of factors: the type of cancer (the prognosis is excellent for thyroid cancer, but much less so for pancreatic cancer), the extent of the cancer to the timing of diagnosis, cell malignancy, availability of effective treatment, etc.
The most common method used to determine the severity of cancer is the TNM classification (Tumor, Node, Metastases).
- Stage T (1 to 4) describes the size of the tumor.
- Stage N (0 to 3) describes the presence or absence of metastases in nearby lymph nodes.
- Stage M (0 or 1) describes the absence or presence of metastases distant from the tumor.
The stages of cancer
Cancer usually takes several years to form, at least in adults. There are 3 stages:
- Initiation. The genes of a cell get damaged; this happens frequently. For example, carcinogens in cigarette smoke can cause such damage. Most of the time, the cell fixes the error automatically. If the mistake is irreparable, the cell dies. This is called apoptosis or cellular “suicide”. When the cell is not repaired or destroyed, the cell remains damaged and moves on to the next step.
- Promotion. External factors may or may not stimulate the formation of a cancer cell. These can be lifestyle habits, such as smoking, lack of physical activity, poor diet, etc.
- Progression. The cells proliferate and the tumor forms. In some cases, they can invade other parts of the body. In its growth phase, the tumor begins to cause symptoms: bleeding, fatigue, etc.
Characteristics of a cancer cell
- Out of control multiplication. Cells reproduce all the time, despite the signals to stop growth.
- Loss of utility. Cells no longer perform their original functions.
- Immortality. The process of cell “suicide” is no longer possible.
- Resistance to immune system defenses. Cancer cells outsmart their usual “killers”, NK cells, and other cells believed to limit their progression.
- Formation of new blood vessels in the tumor called angiogenesis. This phenomenon is essential for the growth of tumors.
- Sometimes invasion of nearby tissues and other parts of the body. These are the metastases.
The changes that take place in a cell’s genes when it becomes cancerous are passed on to its descendants.
Cancer manifests itself in a very variable way. It usually evolves over many years, often without causing symptoms. However, the following symptoms can be signs of cancer. In their presence, talk to your doctor:
- A palpable mass, especially if it increases in size: a nodule in a breast, under the skin, in a lymph node, etc.
- A mole or patch on the skin that changes in appearance, color or size, or is bleeding.
- Bleeding: blood in sputum, urine, or stool. For women, vaginal blood loss not related to period or after menopause.
- Persistent symptoms: unexplained cough and hoarseness for more than 4 weeks, difficulty swallowing, nausea and vomiting, a sore that does not heal in 3 weeks, diarrhea or constipation for 6 weeks or more.
- A retraction of the nipple
- Discharge from the nipple.
- Recurrent and violent headaches.
- Extreme fatigue.
- Rapid and unexplained weight loss.
People at risk of cancer
Some families are more affected by cancer. There are genes that predispose to cancer, passed down from generation to generation. This can be the case for breast, ovarian and colon cancers. Even in people whose genetic makeup predisposes them to cancer, the risk of developing cancer one day also largely depends on lifestyle habits and where they live and work.
People who have had cancer in the past.
Scientific research has uncovered risk factors for most cancers. Moreover, two thirds of cancers are caused by lifestyle habits. However, it is very difficult to narrow down the responsibility for each of the following risk factors in an individual’s life, as the disease develops over several years and is often multifactorial.
There are two main risk factors:
- Tobacco. Smoking is responsible for almost a third of cancer-related deaths, and is not just related to lung cancer. The carcinogens contained in cigarette smoke increase the risk of several cancers: throat, bladder, liver, etc.
- Food. Unhealthy food is responsible for around 30% of cancers in the West, and 20% in developing countries, according to the World Health Organization: too many calories, red meats and cold cuts, fat, salt and sugar, and not enough fruits, vegetables and whole grains contribute to the rise of cancer.
Other important risk factors
- Overweight. These physical conditions increase the risk of many cancers.
- Alcohol. The digestion of ethanol creates metabolites that alter the genes of cells (mutagens).
- Lack of physical inactivity. People who are more active are less at risk of certain types of cancer.
- Sun exposure. Long-term exposure to high-dose ultraviolet (UV) rays can cause skin cancer.
- Environmental contaminants (air, water and soil). Cardiovascular disease, respiratory problems and cancer are influenced by the presence of toxic chemicals in the environment.
- Infections. In industrialized countries, 5% of cancer cases are attributable to infections, and across the world, no less than 18%. Examples: papillomavirus (cancer of the cervix), hepatitis B and C viruses, and the bacteria Helicobacter pylori (cancer of the stomach).
- Exposure to radioactive substances. The exploitation of nuclear energy carries risks for humans. The Chernobyl nuclear accident, for example, resulted in many cancer deaths.
Can stress cause cancer?
Many studies have investigated stress as a risk factor for cancer. Animal studies have measured biological changes linked to stress: reduction in immune factors, hormonal changes, etc., but it is not necessarily obvious that the results can be transposed to humans. Epidemiological studies face several methodological difficulties, and their results are often contradictory.
- the first did not find a clear association between stress level and risk of breast cancer.
- the second found an association between the number of stressful life events and the risk of breast cancer.
A meta-analysis in 2013 has also demonstrated an association between breast cancer and stressful life events.
In 2013, another large-scale meta-analysis looked at the link between the level of stress in the workplace and the occurrence of breast, prostate, lung and colorectal cancers. No association was found between the level of stress at work and the risk of developing one of these four cancers. However, certain professional environments can contribute to an increase in the risk of cancer, through exposure to certain carcinogenic substances.
All in all, the knowledge currently available is contradictory and does not make it possible to establish a causal link between stress and an increased risk of cancer.
Only an association with an increased risk of cardiovascular disease has been demonstrated. On the other hand, stress can be at the origin of behaviors at risk for health, in particular by increasing the risks of cancer related to excessive consumption of alcohol, tobacco, bad eating habits (overeating for example), lack of physical activity, etc.
Conversely, it is well established that cancer, once diagnosed, can cause significant stress in the patients and those around them. This stress can be expressed through psychological, relational or behavioral difficulties and must be taken into account and supported during and after the illness.
Prevention of cancer
The measures described here are also extremely important for people with cancer, in addition to medical treatments, but unfortunately remain underused. They can help slow the progression of cancer and prevent recurrence.
Main preventive measures
Stop smoking. For useful advice, see our Smoking sheet.
Follow the basic rules of anti-cancer nutrition as much as possible. Some foods have an anticancer effect, others may have the opposite effect. Below are the general recommendations.
Eat fresh fruits and vegetables a minimum of 5 servings per day:
- the cruciferous family (broccoli, cabbage, cauliflower, turnip, rapini, rutabaga, etc.)
- alliaceae (onions, garlic, shallot)
- dark green vegetables
- citrus fruits (lemon, lime (lime), orange, grapefruit)
- small fruits (blueberries, raspberries, strawberries, etc.)
- Whole grains
- Legumes and soy
- Turmeric. Ideally, consuming turmeric with pepper, which greatly increases the absorption of turmeric by the body
- Green tea
Eliminate or avoid as often as possible:
- excess calories, fat and salt;
- refined sugars and white flour;
- meals prepared in industry;
- red meats and cold cuts (ham, bacon, sausage, etc.);
- marinated, canned, smoked, fried or processed foods;
- flame cooked meat (barbecue). Maceration of meat in a marinade containing an acidic element (such as lemon juice) reduces the formation of these toxins.
- Alcohol consumption
In light of the most recent studies, minimal alcohol consumption appears to be safe. But experts advise women to limit their alcohol intake to less than one drink per day, and men to less than two drinks per day.
According to some experts, whole-grain fruits, vegetables and cereals from organic farming have better nutritional value than their counterparts from industrial agriculture. However, this remains to be demonstrated.
Other preventive measures
- Be physically active: a minimum of 30 to 45 minutes of physical activity per day.
- Protect yourself from sexually transmitted infections.
- Avoid being in contact with carcinogenic substances (herbicides and pesticides, radiation, etc.).
- Do not expose yourself to the sun for prolonged periods without adequate protection.
- In the event of persistent stress or anxiety, find the means to cope better (meditation, deep breathing, psychotherapy approach if necessary).
For some types of cancer, early detection significantly increases the chances of survival. In some cases, screening is only for individuals whose family members have or have had cancer. Consult our specific sheets on the various forms of cancer to find out more.
Treatment of cancer
Cancer treatment depends on a multitude of factors: type of cancer, size and location, course of the disease and the person’s state of health. It usually takes several months. Then, regular follow-up is offered, due to the possibility of relapse.
Depending on the degree of cancer progression, 3 therapeutic approaches are possible:
- A curative treatment, which aims to cure cancer.
- Adjuvant therapy, which is given alongside the main treatment, to increase the chances of recovery (for example, hormone therapy given before or after surgery for prostate cancer).
- Palliative treatment, aimed at relieving symptoms or prolonging life, when the chances of recovery are very low.
Treating cancer is quite a challenge: killing diseased cells while preserving healthy cells is a real scientific and technical problem. Radiation therapy, for example, also destroys healthy cells near the tumor. As for chemotherapy treatments, some of them will affect the whole body, especially rapidly growing cells, such as those in the scalp, digestive tract and blood. In this case, the side effects can be significant: reduced immune function, anemia, digestive problems and hair loss. Researchers are hard at work to develop drugs that only attack cancer cells.
Types of possible medical treatments
- Surgery. If possible, the tumor is removed by surgery and the treatment is supplemented with radiation therapy and chemotherapy to remove any remaining cancer cells. This is the oldest cancer treatment and arguably the most effective when the tumor is still confined to one area of the body, that is, it has not infiltrated neighboring tissues.
- Radiotherapy. Using different sources of ionizing radiation, depending on the type of tumor, this treatment is often required after surgery. It aims to destroy cancer cells that may remain and to prevent local recurrences. The rays also kill normal cells. Ionizing rays are emitted either by a radiotherapy machine or by radioactive substances introduced into the patient’s body near the tumor (brachytherapy). In Canada and the United States, about half of cancer patients receive radiation therapy.
- Chemotherapy. Chemotherapy involves giving chemicals by injection or in tablet form that kill diseased cells. There are several, which have different mechanisms of action and different side effects. Its use depends on the malignancy of the tumor, its origin and its stage of development. It is often used when the tumor comes back and when there is metastasis. Chemotherapy is sometimes used before surgery to reduce the size of the tumor and make it easier to remove.
- Hormone therapy. Hormone therapy can help control and cure breast or prostate cancer, which is sometimes hormone-dependent (their growth can be stimulated by hormones, such as estrogen or testosterone). It is often aimed at lowering the level of certain hormones in the body, or preventing the tumor from using these hormones to grow.
- Immunotherapy. Among the main chemicals active in the immune system are cytokines – including interferons and interleukins. In patients with an already strong immune system and in whom the cancer is still at an early stage, cytokines can be injected to boost the body’s immune function. In addition, new immunotherapy treatments are being developed. They consist of producing a vaccine that stimulates the activity of the patient’s immune system against their tumor.
- Bone marrow transplant. This treatment is only used for cancers that affect immune cells (eg lymphoma).
Tumor angiogenesis is the process by which new small blood vessels form around a tumor. These vessels allow the tumor to feed and grow. Their formation is stimulated by substances secreted by cancer cells. Several chemotherapy and hormone therapy drugs aim to stop the phenomenon of angiogenesis so as to “starve” the tumor.
Psychological and social support
The disease almost always has psychological impacts, which vary over the stages: diagnosis, treatment, reconciliation with family life and work, remission, etc. The diagnosis often results in an emotional shock. The feeling of losing control over one’s life, even temporarily, can be overwhelming, as can being ignorant of what lies ahead.
The support of family, relatives or specialized help is very valuable in order to better cope with these upheavals.
Specialized help can take all kinds of forms: consultation with a psychologist, psychotherapist, psychiatrist, social worker or nurse, participation in a support group, or meeting with other patients on the Internet.
Research led by Alastair Cunningham at the University of Toronto and David Spiegel at Stanford University shows that participating in group psychotherapy generally decreases stress, provides greater appreciation for life and helps make sense of it. Other research, however preliminary and controversial, suggests that lifespan may be extended in some people with cancer who take such a step in psychotherapy with great personal commitment.
Note. Experts warn against the simplistic idea that positive thinking can cure cancer, or the disease is due to psychological conflict that, when solved, will lead to recovery.
If you have just found out that you have cancer, you are most likely confused and worried. It is normal for the first reaction to be one of panic. Despite advances in medicine, the diagnosis of cancer remains a threatening announcement. The first step is to inform yourself well once the shock has passed. Stay away from people who offer “miracle cures”; miracle cures do not exist. If you want to explore unconventional avenues, be cautious and ensure that no one exploits or abuses your vulnerability.
Fighting cancer takes a lot of courage and determination. Don’t be alone, rely on your family, friends and family; seek help from a support group if necessary. Good luck!