Causes and risk factors
What causes cancer?
There is no one single cause for cancer. Scientists believe that it is the interaction of many factors together that produces cancer. The factors involved may be genetic, environmental or constitutional characteristics of the individual.
Diagnosis, treatment and prognosis for childhood cancers are different than for adult cancers. The main differences are the survival rate and the cause of the cancer. The survival rate for childhood cancer is about 75 percent, while in adult cancers the survival rate is 60 percent. This difference is thought to be because childhood cancer is more responsive to therapy, and a child can tolerate more aggressive therapy.
Childhood cancers often occur or begin in the stem cells, which are simple cells capable of producing other types of specialized cells that the body needs. A sporadic (occurs by chance) cell change or mutation is usually what causes childhood cancer. In adults, the type of cell that becomes cancerous is usually an “epithelial” cell, which is one of the cells that line the body cavity — including the surfaces of organs, glands or body structures — and cover the body surface. Cancer in adults usually occurs from environmental exposures to these cells over time. Adult cancers are sometimes referred to as “acquired” for this reason.
What are the risk factors for cancer?
As mentioned, some cancers, particularly in adults, have been associated with certain risk factors. A risk factor is anything that may increase a person’s chance of developing a disease. A risk factor does not necessarily cause the disease, but it may make the body less resistant to it. People who have an increased risk of developing cancer can help to protect themselves by scheduling regular screenings and check-ups with their physician and by avoiding certain risk factors. Cancer treatment has been proven to be more effective when the cancer is detected early. The following risk factors and mechanisms have been proposed as contributing to the development of cancer.
- Lifestyle factors – Lifestyle and environmental factors such as smoking, high-fat diet, exposure to ultraviolet (UV radiation from the sun) or exposure to chemicals (cancer-causing substances) in the work place over long periods of time may be risk factors for some adult cancers. Most children with cancer, however, are too young to have been exposed to these lifestyle factors for any extended time.
- Genetic factors – Family history, inheritance and genetics may play an important role in some adult and childhood cancers. It is possible for cancer of varying forms to be present more than once in a family. Some gene alterations are inherited. However, this does not necessarily mean that the person will develop cancer. It indicates that the chance of developing cancer increases. It is unknown in these circumstances if the disease is caused by a genetic mutation, other factors or simply coincidence.
- Virus exposure – Exposure to certain viruses, such as the human papillomavirus and human immunodeficiency virus (HIV; the virus that causes acquired immune deficiency, or AIDS), have been linked to an increased risk of developing certain types of cancers. Possibly, the virus alters a cell in some way. That cell then reproduces an altered cell and, eventually, these alterations become a cancer cell that reproduces more cancer cells. Cancer is not contagious and a person cannot contract cancer from another person who has the disease.
- Environmental exposures – Environmental exposures such as pesticides, fertilizers and power lines have been researched for a direct link to childhood cancers. There has been evidence of cancer occurring among nonrelated children in certain neighborhoods and/or cities. Whether prenatal or infant exposure to these agents causes cancer, or whether it is a coincidence, is unknown.