HEALTH TOPICS A TO Z

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.

HOW DOES CANCER DEVELOP?

Cancer arises from one single cell. The transformation from a normal cell into a tumour cell is a multistage process, typically a progression from a pre-cancerous lesion to malignant tumours. The development of cancer may be initiated by external agents and inherited genetic factors. Ageing is another fundamental factor for the development of cancer. The incidence of cancer rises dramatically with age, most likely due to risk accumulation over the life course combined with the tendency for cellular repair mechanisms to be less effective as a person grows older.

HOW CAN THE BURDEN OF CANCER BE REDUCED ?

The existing body of knowledge about the causes of cancer and about interventions to prevent and manage cancer is extensive. Cancer control is understood as public health actions which are aimed at translating this knowledge into practice. It includes the systematic and equitable implementation of evidence-based strategies for cancer prevention, early detection of cancer and management of patients with cancer.

• Up to one third of the cancer burden could be reduced by implementing cancer preventing strategies which are aimed at reducing the exposure to cancer risk mainly by:
• changes in tobacco and alcohol use, and dietary and physical activity patterns
• immunization against HPV infection
• the control of occupational hazards
• reducing exposure to sunlight
• Another third of the cancer burden could be cured if detected early and treated adequately.
• Early detection of cancer is based on the observation that treatment is more effective when cancer is detected earlier. The aim is to detect the cancer when it is localized. There are two components of early detection programmes for cancer:
• Education to promote early diagnosis by recognizing early signs of cancer such as: lumps, sores, persistent indigestion, persistent coughing, and bleeding from the body's orifices; and the importance of seeking prompt medical attention for these symptoms.
• Screening is the identification by means of tests of people with early cancer or pre-cancer before signs are detectable. Screening tests are available for breast cancer (Mammography) and Cervical cancer (Cytology tests).
• Treatment of cancer is aimed at curing, prolonging life and improving quality of life of patients with cancer. Some of the most common cancer types such as breast cancer, cervical cancer and colorectal cancer have a high cure rate when detected early and treated according to best evidence. The principal methods of treatment are surgery, radiotherapy and chemotherapy. Fundamental for adequate treatment is an accurate diagnosis by means of investigations involving imaging technology (ultrasound, endoscopy, radiography) and laboratory (pathology).
• Relief from pain and other problems can be achieved in over 90% of all cancer patients by means of palliative care. Effective strategies exist for the provision of palliative care services for cancer patients and their families, even in low resource settings.

WHO'S STRATEGY FOR PREVENTION AND CONTROL OF CANCER

Following the adoption of a Cancer Prevention and Control Resolution at the 58th WHA on May 2005, WHO is developing the Global WHO Cancer Control Strategy. The Strategy aims at reducing the cancer burden and cancer risk factors as well as improving the quality of life of patients and their families worldwide by means of planning and implementing cancer prevention and control strategies. The cancer control strategy is integrated into the overall WHO chronic disease prevention and control framework of the Department of Chronic Diseases and Health Promotion. The cancer control strategy is based on the following guiding principles:

• People-centered: the ultimate goal is to improve the well-being of the people, communities, families and individuals.
• Equity: the strategy focuses on the needs of low-and middle-income countries and of vulnerable and marginalized populations.
• Ownership: the strategy guarantees the strong commitment and active involvement of key stakeholders in each stage of the decision-making process and implementation.
• Partnership and multisectoral approach: the strategy ensures the wide participation and collaboration of all sectors: public and private,
• Sustainability: the strategy emphasizes the need for national governments and partners collectively strive for financial and technical self-reliance, to ensure the continuation of benefits from established programmes after major assistance has been completed.
• Integration: the strategy is embedded within the overall framework of chronic disease prevention and control and other related areas (such as environmental health, communicable diseases, etc).
• Stepwise approach: the strategy considers the implementation of interventions, at a national or sub-national level, in a sequential manner.
• Evidence-based: the strategy is based on research results, programme evaluation, economic analysis, best practice, and lessons from countries.

WHO, in cooperation with its cancer research agency, the International Agency for Research in Cancer (IARC), and other organizations of the United Nations system, will provide the leadership for international cancer prevention and control and will develop the following actions:

• Advocacy and political commitment for cancer prevention and control
• Generation of new knowledge and dissemination and diffusion of existing knowledge to facilitate the application and programme delivery of evidence-based approaches to cancer control
• Development of standards and tools for guiding effective cancer control planning and implementation of evidence-interventions for prevention, early detection, treatment and palliative care
• Facilitating the development of multisectoral networks of cancer control partners at the global, regional and national levels
• Building capacity for developing and implementing effective policies and programmes and strengthening health systems
• Provision of technical assistance for the rapid, effective and efficient translation of evidence-based cancer control interventions into public health policies and programmes in developing countries