CANCER

WHAT IS CANCER?

Cancer is a generic term for a group of more than 100 diseases that can affect any part of the body. Other terms used are malignant tumours and neoplasms. One defining feature of cancer is the rapid creation of abnormal cells which grow beyond their usual boundaries, and which can invade adjoining parts of the body and spread to other organs, a process referred to as metastasis. Metastases are the major cause of death from cancer.

FACTS ABOUT CANCER

Cancer is a leading cause of death worldwide. From a total of 58 million deaths worldwide in 2005, cancer accounts for 7.6 million (or 13%) of all deaths. The main types of cancer leading to overall cancer mortality are:

• lung (1.3 million deaths/year);
• Stomach (almost 1 million deaths/year);
• Liver (662,000 deaths/year);
• Colon (655,000 deaths/year) and
• Breast (502,000 deaths/year).

More than 70% of all cancer deaths in 2005 occurred in low and middle income countries. Deaths from cancer in the world are projected to continue rising, with an estimated 9 million people dying from cancer in 2015 and 11.4 million dying in 2030.

The most frequent cancer types world wide are:

• Among men (in order of number of global deaths): lung, stomach, liver, colorectal, oesophagus and prostate.
• Among women (in order of number of global deaths): breast, lung, stomach, colorectal and cervical.

QUICK CANCER FACTS

• 40% of cancer can be prevented (by a healthy diet, physical activity and not using tobacco).
• Tobacco use is the single largest preventable cause of cancer in the world. Tobacco use causes cancer of the lung, throat, mouth, pancreas, bladder, stomach, liver, kidney and other types; Environmental tobacco smoke (passive smoking) causes lung cancer.
• One-fifth of cancers worldwide are due to chronic infections, mainly from hepatitis B viruses HBV (causing liver), human papilloma viruses HPV (causing cervix), Helicobacter pylori (causing stomach), schistosomes (causing bladder), the liver fluke (bile duct) and human immunodeficiency virus HIV (Kaposi sarcoma and lymphomas).

WHAT CAUSES CANCER?

Cancer occurs because of changes of the genes responsible for cell growth and repair. These changes are the result of the interaction between genetic host factors and external agents which can be categorized as:

• physical carcinogens such as ultraviolet (UV) and ionizing radiation
• chemical carcinogens such a asbestos and tobacco smoke
• biological carcinogens such as
• infections by virus (Hepatitis B Virus and liver cancer, Human Papilloma Virus (HPV) and cervical cancer) and bacteria (Helicobater pylori and gastric cancer) and parasites (schistosomiasis and bladder cancer)
• contamination of food by mycotoxins such as aflatoxins (products of Aspergillus fungi) causing liver cancer.

Tobacco use is the single most important risk factor for cancer and causes a large variety of cancer types such as lung, larynx, oesophagus, stomach, bladder, oral cavity and others . Although there are still some open questions, there is sufficient evidence that dietary factors also play an important role in causing cancer. This applies to obesity as a compound risk factor per se as well as to the composition of the diet such as lack of fruit and vegetables and high salt intake. Lack of physical activity has a distinct role as risk factor for cancer. There is solid evidence about alcohol causing several cancer types such as oesophagus, pharynx, larynx, liver, breast, and other cancer types.