– With vaccines against HBV and HPV up to 15% of the global cancer incidence in women seems to be preventable, Professor Harald zur Hausen told the 18th UICC International Cancer Congress in Oslo this week. zur Hausen is Scientific Director at the German Cancer Research Centre (Deutsches Krebsforschungszentrum) in Heidelberg, Germany.
Clinical trials for HPV vaccination are presently carried out in various places around the world. Phase II trials have been finished and revealed the safety of the vaccines used and the induction of high antibody titers against some types of high and low risk papillomaviruses.
An effective vaccine against hepatitis B (HBV) has been available since 1981. First data suggesting a protective effect for hepatocellular carcinoma were published from Taiwan in 1997. Results from Gambia show that vaccines for heaptitis B in children is 95 per cent effective in protecting aganinst chronic HBV infection. 10 years after the vaccination, hepatitis B is much lower in vaccinated than in unvaccinated children, and the proportion of chronic carriers has dropped tenfold to just 1% of the total.
Half a million women contract cervical cancer every year
Cancer of the cervix is most common in South America and parts of Africa and Asia. The number of new cases world wide is estimated to about 500 000 new cases a year. This cancer is the sixth most common cancer in the world, accounting for 5,8 per cent of the 9,9 million new cancer cases in 2000.
More than 80 per cent of the victims live in areas where there is no screening, and will not be for the foreseeable future. Because the cancers in these areas often are diagnosed in an advanced stage, most patients die from the cancer. The disease burden is increasing.
One example is Zimbabwe where cervical cancer is the most commonly registered cancer (27 %). The peak age for diagnosis is 47 years. About 80 per cent of the patients present with advcanced stages. This makes curative treatment difficult. Two hospitals provide surgery and radiation for a population of 13 million people.
While waiting for vaccines to prevent cervical cancer, new screening strategies are needed in low income countries which have no infrastructure for PAP smear screening. So far visual inspection with acetic acid and HPV-detection seem to be the most promising methods. Screening programmes have to be tailored for individual resource and socio-cultural setting.
In contrast up to 80 per cent of cervical cancer in developed countries are prevented by screening using PAP smear. In these countries it is discussed if too much resources are spent on screening and treatment of pre-invasive lesions. Due to surgical intervention, the over-all risk of progression of pre-invasive disease to invasive disease is probably less than 5%.
Liver cancer most abundant in east Asia and parts of Africa
Liver cancer is the fifth most frequent cancer of the world, affecting both men and women. 5,8 per cent of all new cancer cases worldwide are liver cancer – about 570 000 of 9,9 million new cases in 2000.
Liver cancer is the most common cancer in sub-Saharan Africa. The cancer is also frequent in east Asia, particularly China. This is due to the high prevalence of chronic hepatitis B virus infection and exposure to the food borne carcinogen aflatoxin B1.
Hepatitis B is also a main cause of disabling liver disease in large parts of the world. In some countries virtually the entire population is exposed to the virus, and 5 – 30% are chronic carriers.