Forty percent of the 12 million people diagnosed with cancer each year could avert the killer disease with protection against infections and lifestyle changes, experts said on Tuesday ahead of World Cancer Day on Feb. 4.

* WHAT IS CANCER?

-- Cancer is a generic term for a large group of diseases that can affect any part of the body. Other terms used are malignant tumours and neoplasms.

-- A defining feature of cancer is the rapid creation of abnormal cells that grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other organs. This process is referred to as metastasis. Metastases are the major cause of death from cancer.

* KEY RISKS:

-- Some key risk factors for cancer that can be avoided include smoking -- responsible for 1.8 million cancer deaths per year (60 percent of these deaths occur in low- and middle-income countries).

-- Being overweight, obese or physically inactive -- together responsible for 274,000 cancer deaths annually.

-- Excessive alcohol intake -- responsible for 351,000 cancer deaths per year.

-- Sexually transmitted human papilloma virus (HPV) infection -- responsible for 235,000 cancer deaths per year.

* KEY FACTS AND NUMBERS:

-- Cancer is a leading cause of death worldwide: it accounted for 7.4 million deaths (around 13 percent of all deaths) in 2004.

-- Lung, stomach, liver, colon and breast cancer cause the most cancer deaths each year.

-- The most frequent types of cancer worldwide (in order of the number of global deaths) are:

Among men -- lung, stomach, liver, colorectal, oesophagus and prostate.

Among women - breast, lung, stomach, colorectal and cervical.

-- Ageing is another fundamental factor for the development of cancer. The incidence of cancer rises dramatically with age, with the overall risk accumulation combined with the tendency for cellular repair mechanisms to be less effective, as a person grows older.

-- The main types of cancer leading to overall cancer mortality each year are:

Lung (1.3 million deaths/year):

Stomach (803 000 deaths)

Colorectal (639 000 deaths)

Liver (610 000 deaths)