How does cancer develop?
The human body consists of trillions of cells. Every day, new cells grow and multiply in a process called cell division. A normal cell first grows, then divides and finally dies.
Cancer cells, on the other hand, undergo genetic changes leading them to divide uncontrollably. These cells can then invade nearby tissues and spread to other parts of the body.
The development of cancer is measured in stages and is determined by a few different factors, including the size and location of the tumour:
Cancer stages:
Stage 0: Abnormal cells are present but have not spread to nearby tissues.
Stage 1 (early-stage): Cancer has not infiltrated deeply into nearby tissues, nor has it spread to lymph nodes or locations away from the primary tumour.
Stage 2 (localised): Tumour cells have spread deeper into neighbouring tissues, but not to distant sites in the body.
Stage 3 (regional spread): Cancer has grown more deeply into neighbouring tissues and spread to lymph nodes but has not spread to distant sites in the body.
Stage 4 (distant spread): Cancer cells have spread beyond nearby tissues and into lymph nodes and parts of the body, including organs, potentially far from the original site. This stage is often referred to as advanced cancer.
The most common types of cancer
According to the US-based National Cancer Institute, there are more than 100 different types of cancer.
Cancer can start almost anywhere in the body, including bones, organs and skin. The types of cancer are usually named after the organs or tissues where they originate.
The two most common types of cancer worldwide are breast and lung cancer, contributing 12.5 percent and 12.2 percent, respectively of the total number of new cancer diagnoses in 2020, according to the World Health Organization (WHO).
Lung cancer is the most common type of cancer among men, contributing 15.4 percent of all new cancer diagnoses in 2020. Among women, breast cancer is the most common, accounting for about one-quarter (25.8 percent) of the total new cases in 2020.
How many people die from cancer?
Not all cancers cause death. However, it is important to identify and treat cancer as early as possible. When identified early, cancer is more likely to respond to treatment and can result in a greater chance of survival.
In addition to early diagnosis, cancer screening is an effective way of identifying abnormal cells before they may become cancer. Several screening tests have been shown to detect cancer early and to reduce the chance of dying from that cancer.
In 2019, more than 10 million people died from cancer around the world, making it the second leading cause of death after cardiovascular diseases, according to the Institute for Health Metrics and Evaluation (IHME). Almost half, 46 percent, of all people who die from cancer are aged 70 or older.
Most common cancer deaths
The most common cause of cancer death is lung cancer, accounting for 1.8 million deaths worldwide in 2020, according to the WHO. The second most common cause is colorectal cancer (935,173 deaths), followed by liver cancer (830,180 deaths) and stomach cancer (768,793 deaths).
About one-third of deaths from cancer are due to tobacco use, high body mass index, alcohol consumption, low fruit and vegetable intake, and lack of physical activity, the WHO says.
Cancer rates across the world
According to the World Cancer Research Fund International (WCRF), 18,094,716 cases of cancer were diagnosed globally in 2020.
The age-standardised rate for all cancers diagnosed in 2020 was 190 per 100,000 people. The rate was higher for men (206.9 per 100,000) than for women (178.1 per 100,000).
In 2020, the highest cancer rate was in Denmark at 334.9 people per 100,000, followed by Ireland (326.9 per 100,000) Belgium (322.8 per 100,000), Hungary (321.6 per 100,000) and France (320.1 per 100,000).
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