What is Cancer?

Cancer is a generic term for a wide variety of diseases whose causes, nature and manifestations can vary widely. There is no clear definition of cancer.

Cancer is a disease of the elderly. As the population ages, the incidence of cancer also increases.

However, more and more are healing from cancer. The potential for healing depends on many factors, such as the type of cancer and the extent of the tumor. Many of the patients who cannot be permanently cured live with advanced cancer treatments.

The human body is made up of cells. Normally, the distribution of cells in the body is carefully regulated, so that new cells are created as the old ones reach the end of their life cycle. Sometimes, however, the cell begins to grow and divide abnormally. The mass formed from uncontrolled dividing cells is called a tumor. Tumors can be benign or malignant.

Cancer cells do not always form a dense tumor. For example, leukemia is a cancer of the blood-forming tissues, in which the cancer cells continue to circulate in the body and still behave to some extent as healthy cells. In the end, they take up so much space on healthy cells that normal cell functions are prevented.

How does cancer develop?

The origin of cancer is a multistep event in which damage to a cell’s genetic material renders a normal cell malignant. The damage gradually accumulates in the cell growth regulating system.

Cancer comes from a genetic defect. Human genetic factors, or genes, are located inside cells in structures called chromosomes. Genes direct cellular functions such as their distribution. Genes can be altered, or mutated, if the mechanisms that regulate cell division fail. One gene defect is usually not enough to cause cancer. Cancer occurs when mutations occur in several genes that play an important role in the regulation of cell growth and differentiation.

The so-called cancer genes are normal genes that direct cell function and are just damaged.

There are two types of cancer genes:

• oncogenes, cancer-causing genes whose activation causes uncontrolled cell division
• growth inhibitory genes or anti-cancer genes whose carcinogenic effect is due to their cessation of action

Genetic damage is constantly occurring in many cells. However, the human body has a sophisticated defense system that corrects damage. If the system fails, the damaged cells may begin to divide uncontrollably, eventually leading to cancer.

There are billions of cancer cells in a cancerous tumor. The cancer cell must divide many thousands of times before the tumor is even pea-sized. Thus, it may take years for the tumor to show up on an X-ray or be palpable. Sometimes, however, a tumor can also grow much faster.

What Causes Cancer?

Cancer is caused by damage to genes. Changes may be the result of accidental exposure or exposure to a carcinogen.

Carcinogens are called carcinogens. For example, the carcinogen may be a chemical such as certain molecules of tobacco smoke. Habitat factors, the virus and hereditary factors can cause cancer.

In most cases of cancer, one single cause of cancer cannot be identified.

The risk factors for cancer can be roughly divided into the following categories:

1. biological or intrinsic factors such as age, sex, hereditary genetic defects and skin type
2. environmental exposures, such as radon and UV radiation and fine particles
3. occupational hazards, ie carcinogens such as many chemicals, radioactive materials and asbestos
4. lifestyle factors

Lifestyle-related carcinogens include, but are not limited to:

• tobacco
• alcohol
• ultraviolet radiation from the sun
• some nutritional factors (such as nitrites and polyaromatic hydrocarbons from barbecue)

Carcinogens at work and in the living environment include:

• asbestos fibers
• tar and pitch
• polycyclic hydrocarbons (eg benzopyrene)
• certain metal compounds
• certain plastic chemicals (eg vinyl chloride)

Bacteria and viruses can predispose to cancer:

• Helicobacter pylori (Helicobacter pylori, which causes stomach ulcer)
• HBV, HCV (hepatitis viruses that cause inflammation of the liver)
• HPV (human papilloma virus, a papilloma virus that causes changes in eg cervical cells)
• EBV (Epstein-Barr virus, a herpesvirus virus that causes inflammation of the larynx in the throat)

Radiation can cause cancer:

• ionizing radiation (eg X-ray, soil radon)
• non-ionizing radiation (ultraviolet radiation from the sun)

Some drugs can predispose to cancer:

• certain chemo-blockers
• certain hormones
• medicines that cause immunodeficiency

In 5-10% of cancers, hereditary predisposition plays a major role in the onset of the disease.

Cancer genetics

According to current estimates, only about one in 10 cases of cancer is associated with hereditary predisposition. Cancer is not inherited.

Cancer is a common disease, and almost every family has a number of members who suffer from cancer. However, this does not generally mean that families have a hereditary predisposition to cancer. The vast majority of cancer cases originate from the combined effect of hereditary as well as external influences, such as environmental and lifestyle factors.

Cancer is not inherited. It is only the genetic defect that can lead to cancer that is inherited, which means that the predisposition to getting cancer, or increased risk, can be inherited. However, this is not common. According to current estimates, only about one in 10 cases of cancer is associated with hereditary predisposition.

An inherited genetic defect is not necessarily passed on to all members of the same family, and not everyone who receives the same defective gene will develop cancer.

It is also worth remembering that the genetic changes that occur in cancerous tumours are not passed on genetically to one’s offspring.

How is hereditary cancer identified?

A genetic disposition to cancer can be identified by the onset of cancer occurring at a very young age or that many closely related members of the same family suffer from the same type of cancer.

The genetic defects that incur a predisposition to cancer are varied. They can be rare, they may involve genetic changes that pose a high cancer risk, or ones that carry only a low risk, or then somewhere in between.

Nowadays, we know about some of the genetic defects that carry a bigger cancer risk, but not all. Many genes are still being investigated.

Hereditary breast cancer

Breast cancer is the most common form of cancer among women. Nearly 5 000 women and some 20 men fall ill with the disease. From what we know at present, about 10 per cent of breast cancer is hereditary. The best-known genes that carry a high risk of causing breast and ovarian cancer are the BRCA1 and BRCA2 genes. There is also a susceptibility gene, which is linked to a moderate risk of breast cancer.

It is good to find out about one’s inherited breast cancer predisposition if

• At least three of four relatives from the same side of the family have had breast or ovarian cancer
• A close relative had cancer at a young age
• There has been both breast and ovarian cancer in the same family
• A man in one’s family has had breast cancer.

Hereditary colorectal cancer

About two-three per cent of the new cases of colorectal cancer detected each year are hereditary.

We refer to hereditary colorectal cancer if

• At least three close family relatives have had colorectal cancer and at least one of them is under 50 years old.
• There has been, in addition to colorectal cancer, endometrial, small bowel, urethral or renal pelvis cancer among close family relatives.

There are about 250 extended families in Finland in which gene defect causing a predisposition to hereditary non-polyposis colorectal cancer (Lynch Syndrome) has been detected.

Can we detect cancer with gene tests?

Cancer cannot be found using gene testing, but with the help of current genetics research we can detect some cancer-predisposing gene defects.

At present, there is no simple genetic test for those interested in being tested. Genetic tests are only used when there is clear evidence of a possible hereditary predisposition to cancer.

Cancer is not inherited

It is worth bearing in mind that cancer is not inherited. It is only the genetic defect that may cause cancer that is inherited. We therefore speak of an inherited predisposition to cancer.

An inherited predisposition to cancer increases the risk of a person getting cancer. According to current estimates, some one out of ten cases of cancer is associated with hereditary predisposition.

Cancer symptoms

Cancer has numerous symptoms. It may be asymptomatic for a long time or it may involve only very general symptoms, such as fatigue or weight loss.

Cancer symptoms usually worsen as time passes. But they can vary substantially. Many types of cancer develop slowly over years.  The spread of the disease also affects the symptoms you have.

Many cancer symptoms resemble those of other illnesses, and it may be that you don’t have any symptoms at all in the early stages of the disease. In most cases it takes years before a cancer becomes big enough to be noticed by palpation.

Cancer symptoms can include:

• A lump or sore that does not heal (including in the mouth)
• A mole that changes in form, size or pigmentation
• Change or damage to the skin that has not been present before and which increases
• Bloody vomit, stool or urine, or a cough producing blood
• Persistent cough
• Prolonged sore throat
• Fatigue
• Changes in bowel movement or urination
• Inexplicable weight loss
• Pain
• Yellowing of complexion

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