World Cancer Day, 2011. What you need to know.

What is it?

Cancers are caused by a series of mutations. Each mutation alters the behavior of the cell somewhat. (Credit: Wikipedia)Cancer is the uncontrolled growth and spread of cells. It can affect almost any part of the body. Other terms used are malignant tumours and neoplasm’s.  One 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.  The growths often invade surrounding tissue and can metastasize to distant sites. Metastases are the major cause of death from cancer. Cancer prevention is an essential component of all cancer control plans because about 40% of all cancer deaths can be prevented.  Many cancers can be prevented by avoiding exposure to common risk factors, such as tobacco smoke. In addition, a significant proportion of cancers can be cured, by surgery, radiotherapy or chemotherapy, especially if they are detected early. 

Q: Are the number of cancer cases increasing or decreasing in the world?

A: Cancer is a leading cause of death worldwide and the total number of cases globally is increasing.

The number of global cancer deaths is projected to increase 45% from 2007 to 2030 (from 7.9 million to 11.5 million deaths), influenced in part by an increasing and aging global population. The estimated rise takes into account expected slight declines in death rates for some cancers in high resource countries. New cases of cancer in the same period are estimated to jump from 11.3 million in 2007 to 15.5 million in 2030.

In most developed countries, cancer is the second largest cause of death after cardiovascular disease, and epidemiological evidence points to this trend emerging in the less developed world. This is particularly true in countries in "transition" or middle-income countries, such as in South America and Asia. Already more than half of all cancer cases occur in developing countries.

Lung cancer kills more people than any other cancer - a trend that is expected to continue until 2030, unless efforts for global tobacco control are greatly intensified. Some cancers are more common in developed countries: prostate, breast and colon. Liver, stomach and cervical cancer are more common in developing countries.

A number of common risk factors have been linked to the development of cancer: an unhealthy lifestyle (including tobacco and alcohol use, inadequate diet, physical inactivity), and exposure to occupational (e.g. asbestos) or environmental carcinogens, (e.g. indoor air pollution), radiation (e.g. ultraviolet and ionizing radiation), and some infections (such as hepatitis B or human papilloma virus infection).

Key risk factors for cancer that can be avoided are:

• tobacco use - responsible for 1.8 million cancer deaths per year (60% of these deaths occur in low- and middle-income countries);
• being overweight, obese or physically inactive - together responsible for 274 000 cancer deaths per year;
• harmful alcohol use - responsible for 351,000 cancer deaths per year;
• sexually transmitted human papilloma virus (HPV) infection - responsible for 235 000 cancer deaths per year; and
• occupational carcinogens - responsible for at least 152,000 cancer deaths per year.

(Credit: Globocan 2008)GLOBAL CANCER STATISTICS:

The problem

Cancer is a leading cause of death worldwide and accounted for 7.6 million deaths (around 13% of all deaths) in 2008.

The main types of cancer are:

• lung (1.4 million deaths)
• stomach (740 000 deaths)
• colorectal (610 000 deaths)
• liver (700 000 deaths)
• breast (460 000 deaths).

More than 70% of all cancer deaths occurred in low- and middle-income countries. Deaths from cancer worldwide are projected to continue to rise to over 11 million in 2030.

What causes cancer?

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. These changes are the result of the interaction between a person's genetic factors and three categories of external agents, including:

• physical carcinogens, such as ultraviolet and ionizing radiation;
• chemical carcinogens, such as asbestos, components of tobacco smoke, aflatoxin (a food contaminant) and arsenic (a drinking water contaminant); and
• biological carcinogens, such as infections from certain viruses, bacteria or parasites.

Ageing is another fundamental factor for the development of cancer. The incidence of cancer rises dramatically with age, most likely due to a buildup of risks for specific cancers that increase with age. The overall risk accumulation is combined with the tendency for cellular repair mechanisms to be less effective as a person grows older.

Risk factors for cancers

(Credit: NIH) Tobacco use, alcohol use, unhealthy diet, and chronic infections from hepatitis B (HBV), hepatitis C virus (HCV) and some types of Human Papilloma Virus (HPV) are leading risk factors for cancer in low- and middle-income countries. Cervical cancer, which is caused by HPV, is a leading cause of cancer death among women in low-income countries.

How can the burden of cancer be reduced?

Knowledge about the causes of cancer, and interventions to prevent and manage the disease is extensive. Cancer can be reduced and controlled by implementing evidence-based strategies for cancer prevention, early detection of cancer and management of patients with cancer.

Modifying and avoiding risks

More than 30% of cancer could be prevented by modifying or avoiding key risk factors, including:

• tobacco use
• being overweight or obese
• low fruit and vegetable intake
• physical inactivity
• alcohol use
• sexually transmitted HPV-infection
• urban air pollution
• indoor smoke from household use of solid fuels.

Prevention strategies:

• increase avoidance of the risk factors listed above
• vaccinate against human papilloma virus (HPV) and hepatitis B virus (HBV)
• control occupational hazards
• reduce exposure to sunlight.

Early detection

Cancer mortality can be reduced if cases are detected and treated early. There are two components of early detection efforts:

• Early diagnosis: The awareness of early signs and symptoms (such as cervical, breast and oral cancers) in order to facilitate diagnosis and treatment before the disease becomes advanced. Early diagnosis programmes are particularly relevant in low-resource settings where the majority of patients are diagnosed in very late stages.
• Screening: The systematic application of a screening test in an asymptomatic population. It aims to identify individuals with abnormalities suggestive of a specific cancer or pre-cancer and refer them promptly for diagnosis and treatment. Screening programmes are especially effective for frequent cancer types that have a screening test that is cost-effective, affordable, acceptable and accessible to the majority of the population at risk. Examples of screening methods:
  • visual inspection with acetic acid (VIA) for cervical cancer in low-resource settings;
  • PAP test for cervical cancer in middle- and high-income settings;
  • mammography screening for breast cancer in high-income settings.

Treatment

Treatment is the series of interventions, including psychosocial support, surgery, radiotherapy, chemotherapy that is aimed at curing the disease or considerably prolonging life while improving the patient's quality of life.

• Treatment of early detectable cancers: Some of the most common cancer types, such as breast cancer, cervical cancer, oral cancer and colorectal cancer have higher cure rates when detected early and treated according to best practices.
• Treatment of other cancers with potential for cure: Some cancer types, even though disseminated, such as leukemias and lymphomas in children, and testicular seminoma, have high cure rates if appropriate treatment is provided.

Palliative care

Palliative care is treatment to relieve, rather than cure, symptoms caused by cancer. Palliative care can help people live more comfortably; it is an urgent humanitarian need for people worldwide with cancer and other chronic fatal diseases. It is particularly needed in places with a high proportion of patients in advanced stages where there is little chance of cure.

Relief from physical, psychosocial and spiritual problems can be achieved in over 90% of advanced cancer patients through palliative care.

Palliative care strategies

Effective public health strategies, comprising of community- and home-based care are essential to provide pain relief and palliative care for patients and their families in low-resource settings.

Improved access to oral morphine is mandatory for the treatment of moderate to severe cancer pain, suffered by over 80% of cancer patients in terminal phase.

WHO response

In 2008, WHO launched its Non-communicable Diseases Action Plan.

WHO and the International Agency for Research on Cancer, the specialized cancer agency of WHO, collaborate with other United Nations organizations and partners in the areas of international cancer prevention and control to:

• increase political commitment for cancer prevention and control;
• generate new knowledge, and disseminate existing knowledge to facilitate the delivery of evidence-based approaches to cancer control;
• develop standards and tools to guide the planning and implementation of interventions for prevention, early detection, treatment and care;
• facilitate broad networks of cancer control partners at global, regional and national levels;
• strengthen health systems at national and local levels;
• provide technical assistance for rapid, effective transfer of best practice interventions to developing countries; and
• coordinate and conduct research on the causes of human cancer, the mechanisms of carcinogenesis, and develop scientific strategies for cancer prevention and control.

RESOURCES:

The World Health Organization, Cancer site

Union For International Cancer Control

Center for Disease Control & Prevention

Cancer Schmancer

- HUMNEWS staff with information provided by the World Health Organization.