Risk factors for
human papillomavirus (HPV)-associated anal disease in HIV-positive gay men are
similar to those already known to increase the risk of HPV-related cervical
disease, research published in the online edition of the Journal of Infectious Diseases shows.
A low CD4 cell count and a
history of infection with chlamydia were both associated with an increased risk
of infection with high-risk HPV types and several smoking characteristics were
associated with the presence of high-grade pre-cancerous anal lesions.
“Many of the
significant risk factors found are similar to established risk factors for
cervical HPV infection and cervical pre-cancer,” write the authors.
Anal cancer is
rare in the general population and almost all cases are caused by persistent
infection with high-risk HPV types. Rates of high-risk HPV are
much higher in gay men living with HIV than other groups.
of anal cancer is very close to that of cervical cancer, which is also
associated with HPV infection. A number of studies have identified the factors
for the progression of HPV-associated cervical disease.
California wanted to see which factors influenced the progression of HPV anal
disease in HIV-positive men who have sex with men.
designed a cross-sectional study involving 305 men who had routine
screening for HPV-associated anal disease between 2009 and 2010.
gathered lifestyle and clinical information and conducted a series of analyses
to see which factors were associated with anal HPV infection and the presence
of high-grade pre-cancerous lesions.
The men had a median age of 53 years (range, 47 to 60 years). The
majority (94%) were taking antiretroviral therapy, 91% had a suppressed viral
load (below 75 copies/ml) and 81% had a CD4 cell count above 350 cells/mm3.
showed that just over a fifth (21%) were negative for high-risk HPV types.
Approximately 50% were infected with a high-risk HPV type without significant
disease and 29% had pre-cancerous anal lesions.
the men with pre-cancerous lesions and men without high-risk anal HPV
infection showed that a CD4 cell count below 350 cells/mm3 (OR,
3.26; 95% CI, 1.122-8.74), a higher number – five and above – of lifetime
male sexual partners (OR, 2.49; 95% CI, 1.12-5.58) and a history of chlamydia
infection (OR, 4.46; 95% CI, 1.23-16.18) were all associated with an increased
risk of pre-cancer. Smoking was also a risk factor.
showed that a history of infection with chlamydia was also a risk factor for
infection with high-risk HPV types (OR, 3.96; 95% CI, 1.13-13.90).
then controlled for confounding factors.
with chlamydia was identified as an independent risk factor for infection with
high-risk HPV types (OR, 4.24; 95% CI, 1.16-15.51). “It has been suggested that
chlamydia may increase persistence of HPV in the cervix, but there is no
evidence for a biological interaction,” note the authors. However, they suggest
that a history of the infection is likely to be an indicator of sexual
behaviour and could therefore be a surrogate marker “for increased exposure to
A low CD4 cell
count also increased the risk of infection with high-risk HPV types (OR, 3.96;
95% CI, 1.13-13.90). The investigators note that this confirms the findings of
previous research showing that “low CD4 cell count (<350 cells/mm3)
was strongly associated with carcinogenic HPV infection”.
Smoking was a risk
factor for pre-cancerous lesions (2.71; 95% CI, 1.43-5.14).
was examined in a further model that controlled for other risk factors for
high-risk HPV infection.
Comparison with men with high-risk strains of HPV but no significant disease showed that
smoking in the past twelve months (OR, 3.20; 95% CI, 1.45-7.09), number of
years smoked (over ten = OR, 3.09; 95% CI, 1.33-7.18), and number of packs
smoked per day (over one = OR, 3.50; 95% CI, 1.19-10.28) were all associated
with an increased risk of pre-cancerous lesions.
have found smoking to be a risk factor for anal cancer,” comment the authors.
“But our study is the first to demonstrate that smoking is a co-factor for anal
pre-cancer, using rigorous histology-confirmed endpoints.” They call for more
studies to assess the relationship between smoking and pre-cancerous lesions.
that risk factors for HPV infection and progression to anal pre-cancer are
similar to established risk factors for cervical cancer progression,” conclude
the authors. “This could facilitate development of anal cancer early detection
efforts, since established tools and approaches from cervical cancer screening
can be adapted for a population at risk of anal cancer.”