world cancer report - iarc

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