world cancer report - iarc
world cancer report - iarc
world cancer report - iarc
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Infectious agent IARC classification 1 Cancer site/<strong>cancer</strong> Number of <strong>cancer</strong> cases % of <strong>cancer</strong> cases<br />
<strong>world</strong>wide<br />
H. pylori 1 Stomach 490,000 5.4<br />
HPV 1, 2A Cervix and other sites 550,000 6.1<br />
HBV, HCV 1 Liver 390,000 4.3<br />
EBV 1 Lymphomas and 99,000 1.1<br />
nasopharyngeal carcinoma<br />
HHV-8 2A Kaposi sarcoma 54,000 0.6<br />
Schistosoma 1 Bladder 9,000 0.1<br />
haematobium<br />
HTLV-1 1 Leukaemia 2,700 0.1<br />
Liver flukes Cholangiocarcinoma 800<br />
Opisthorchis viverrini 1 (biliary system)<br />
Clonorchis sinensis 2A<br />
Table 2.18 The burden of <strong>cancer</strong> caused by infectious agents <strong>world</strong>wide. 1 Group 1= carcinogenic to humans, Group 2A= probably carcinogenic to humans.<br />
2 Applies only to cervical <strong>cancer</strong>.<br />
and oro-pharynx can be attributed to<br />
HPV.<br />
Epstein-Barr virus<br />
Epstein-Barr virus (EBV) infection is ubiquitous.<br />
In developing countries, infection<br />
is acquired in childhood, while in developed<br />
countries infection is delayed until<br />
adolescence [7]. Individuals with high<br />
titres of antibodies to various early and<br />
late EBV antigens have a higher risk of<br />
developing Burkitt lymphoma and<br />
Hodgkin disease (Lymphoma, p237).<br />
Molecular evidence showing that EBV<br />
DNA and viral products are regularly<br />
detected (monoclonally) in <strong>cancer</strong> cells,<br />
but not in normal cells, provides a strong<br />
indication of a causal role for EBV in<br />
nasopharyngeal carcinoma and sinonasal<br />
angiocentric T-cell lymphoma. The association<br />
of EBV is associated with non-<br />
Hodgkin lymphoma mainly in patients<br />
with congenital or acquired immunodeficiency<br />
[7].<br />
Total infection-related 1,600,000 17.7<br />
<strong>cancer</strong>s<br />
Total <strong>cancer</strong>s in1995 9,000,000 100<br />
Human immunodeficiency virus<br />
The prevalence of human immunodeficiency<br />
virus (HIV) infection is highest in sub-<br />
Saharan Africa (15-20%). High levels of<br />
infection are also seen among homosexual<br />
men, intravenous drug users and in subjects<br />
transfused with HIV-infected blood.<br />
An estimated 36 million people <strong>world</strong>wide<br />
are currently living with HIV, and some 20<br />
million people have died as a result of HIVrelated<br />
disease [11]. HIV infection<br />
enhances the risk of Kaposi sarcoma by<br />
approximately 1,000-fold, of non-Hodgkin<br />
lymphoma by 100-fold, and of Hodgkin disease<br />
by 10-fold [6] (Box: Tumours associated<br />
with HIV/AIDS, p60). Increased risk<br />
of <strong>cancer</strong> of the anus, cervix and conjunctiva<br />
has also been observed. In all these<br />
cases, the role of HIV is probably as an<br />
immunosuppressive agent (Immunosuppression,<br />
p68) and hence indirect, the<br />
direct etiological agents being other <strong>cancer</strong><br />
viruses (i.e. human herpesvirus 8<br />
(HHV-8), EBV and HPV) [5-7].<br />
Human T-cell lymphotropic virus<br />
Human T-cell lymphotropic virus (HTLV-<br />
1) infection occurs in clusters in Japan,<br />
Africa, the Caribbean, Colombia and<br />
Melanesia [6]. As many as 20 million<br />
people <strong>world</strong>wide may be infected with<br />
this virus. Spread of the virus is thought<br />
to occur from mother to child (mainly<br />
through breast-feeding beyond six<br />
months), via sexual transmission and as<br />
a result of transfusion of blood cell<br />
products, as well as through intravenous<br />
drug use. A strong geographical<br />
correlation suggests that HTLV-1 is the<br />
main etiological factor in adult T-cell<br />
leukaemia/lymphoma. This disease<br />
occurs almost exclusively in areas<br />
where HTLV-1 is endemic. In addition,<br />
laboratory evidence shows that the<br />
virus is clonally integrated into tumour<br />
cells. An association with tumours of<br />
the cervix, vagina and liver has been<br />
<strong>report</strong>ed, but effects of confounding<br />
and bias cannot be excluded [6].<br />
Chronic infections 57