Implementation

Specifically for viral hepatitis B, four steps should be considered to implement primary prevention nationally.

• Establish collaboration between the NCCP and those in government and NGOs who are interested in hepatitis.
• Perform a sampling survey to determine the carrier rate and transmission modes (horizontal or vertical) for HBV.
• If the HBV carrier rate is more than 10% of adults, implement HBV vaccination.
• Establish a primary prevention program against HBV using the threefold strategy of education, legislation and national leadership as summarized on slide 10 and discussed in more detail below.

Parasites and viruses are the principal concerns related to infections as causes of cancer.

Parasitic Infections

Schistosomiasis causes a substantial amount of bladder cancer in Egypt, Iraq and southeastern Africa. The parasite passes part of its life cycle in snails that live in shallow waters and it is then released into the water where it infects humans by penetrating the skin. The life cycle is continued when infected individuals pass urine and/or feces into the water.

The liver fluke, Clonorchus sinensis, causes a rarer cancer of the bile ducts. It is endemic in Southeast Asia, Thailand, Japan and the Korean peninsula.

Control of cancers caused by these organisms depends on treating the infections. Schistosomiasis cannot be prevented by antiparasitic drugs, but treatment of actual infections may prevent the subsequent development of cancer. Educational measures are also important to reduce the transmission of infections. People are taught to avoid infected water and not to urinate or defecate into water that will be used by others. Environmental measures involve removing or killing the snails that host the Schistosoma organism, or draining the waters where the snails live.

Virus Infections

Primary hepatic carcinoma is the principal cancer attributable to a virus. It results from a chronic infection with hepatitis B virus (HBV). The incidence is particularly high in sub-Saharan Africa and eastern Asia. Viral hepatitis is transmitted in utero or during early childhood. In central Africa and Papua New Guinea Epstein-Barr virus (EBV) has a causal relationship with Burkitt lymphoma which affects children. In Africa, the circumpolar regions and among Chinese populations a causal relation has been noted between EBV and nasopharyngeal carcinoma. In addition, research studies are indicating links between cervical cancer and some subtypes of sexually transmitted human papilloma viruses. Indeed it is seldom really appreciated that cervical cancer can be considered as a sexually transmitted disease (STD). Viruses have been linked by some studies with cancer of the skin and oral cavity as well as some unusual forms of leukemia.

AIDS (acquired immunodeficiency syndrome) is associated with Kaposi sarcoma in about 10% of patients, and also with non-Hodgkin lymphoma. The human immunodeficiency virus (HIV) is transmitted through sexual, parenteral (direct innoculation of blood or its products such as a transfusion or sharing of contaminated needles by intravenous drug users), and perinatal (from an infected woman to her fetus or infant before, during or shortly after birth) routes.

The National Cancer Control Program (NCCP) works through its health educators with relevant agencies in a country that deal with the control of AIDS and STDs. Educational messages should be unified or at least mutually supportive. AIDS control involves reducing the transmission of HIV through "safe" sex, the use of condoms and needle exchange programs. Education is aimed at reducing promiscuous sexual behavior.

Most of these measures will also prevent cervical cancer.

Hepatitis B Infection

HBV vaccine is the first vaccine against a major human cancer. It became available in 1982, and has an outstanding record of both safety and effectiveness. It prevents children or adults who have not yet become infected from developing the chronic carrier state with 95% effectiveness. In many countries chronic carrier rates have dropped from 8-15% to less than 1% in immunized children, in whom a direct reduction in liver cancer has been observed as well. In 1991 WHO called for all countries to add the vaccine into their national immunization programs, and 100 countries have done so as of November, 1998. The poorest countries still cannot afford the vaccine.

Hepatitis B is one of the major diseases of mankind. 2 billion people have been infected and of these more than 350 million are chronic carriers of the virus. Chronic carriers are at high risk of death from hepatic cirrhosis and liver cancer which together kill about one million persons each year. Most people in much of the developing world (sub-Saharan Africa, most of Asia and the Pacific) are infected in childhood and 8-15% of the general population become chronic carriers. In these regions primary hepatocellular carcinoma from HBV can be the number 0ne or two cause of cancer death in men. Infection is much less common in Western Europe and North America where less than 1% of the population are chronic carriers. Much like AIDS, the virus is transmitted by blood and close personal contact, but it is 50 to 100 more infectious than AIDS. Chronic hepatitis is treated with interferon with only partial success, and occasionally with liver transplants – both at great cost. Liver cancer is almost always fatal, developing between ages 35-65 years when people are maximally productive and raising a family.

Thus in an NCCP, immunization against HBV is one of the major preventive steps that can be taken against cancer in jurisdictions where it is a problem.

Evaluation

For HBV control, WHO (1995) recommends the following indicators as examples.

Process Measures
Over 70% of adults receive education about HBV vaccination.
Over 80% of health care workers are educated about HBV vaccination.

Impact Measures
HBV vaccination is incorporated into a country’s immunization program (EPI).
Over 70% of children under age one year are vaccinated against HBV.

Outcome Measures
Short term: None.
Medium term: Reduced incidence of viral hepatitis B. Reduction in carriers of HBV to less than 10% of adults.
Long term: Reduced incidence of primary liver cancer.

WHO (1995) National Cancer Control Programmes: Policies and managerial guidelines. World health Organization, Geneva.
Kramer BS & Johnson KA (1995). Other gastrointestinal cancers: Stomach and liver. In: Greenwald P,
Kramer BS & Weed DL Cancer prevention and control. Marcel Dekker, Inc. New York, p673.
Consult chapters on hepatobiliary cancers (p1087) , bladder cancer (p1300) and AIDS-related malignancies (p2445) In: DeVita VT, Jr, Hellman S & Rosenberg SA (1997) (Ed). Cancer:Principles and practice of oncology. Ed 5 Lippincott-Raven, Philadelphia.
WHO Fact Sheet 204, November 1998. Hepatitis B. World Health Organization, Geneva.

Click to return to slide 10.