Cancer article

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.

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