Ramqvist T. Emerg Infect Dis. 2010;doi:10.3201/eid1611.100452.
A growing proportion of human papillomavirus-positive
oropharyngeal squamous cell carcinoma cases may be attributable to increased
sexual transmission of the disease, recent study data indicate.
“During the past few decades, HPV DNA has been
detected in about 25% of [head and neck squamous cell carcinomas] overall, but
especially in [oropharyngeal squamous cell carcinoma], for which 45%-100% cases
were reported to be HPV positive,” wrote researchers from the Karolinska
Institutet in Stockholm and the Swedish Institute for Infectious Disease
Control in Solna.
To investigate the relationship between HPV and these
cancers, the researchers analyzed data from the Swedish Cancer Registry
collected between 1970 and 2002 in the Stockholm area. Results suggested a
2.9-fold increase in the number of HPV-positive tonsillar cancer, from 23% to
68%, among all 237 samples taken from the 515 patients with the disease.
In a second study, the researchers conducted follow-up
on the incidence of HPV in tonsillar cancer from 2003 to 2007. Data indicated
that the number of HPV-positive cancers increased from 1970 to 2007
(P<.0001) and 2000 to 2007 (P<.01). Additionally, from 2006
to 2007, 93% of tonsillar cancer was HPV-positive, and incidence of
HPV-positive tumors nearly doubled with each decade during the study period.
The incidence of HPV-negative tumors, however, decreased.
Similarly, the prevalence of HPV-positive base of tongue
cancer rose from 1998 to 2007, demonstrating an increase of 54% from 1998 to
1999 and 84% from 2006 to 2007.
“The possible causes for this increase have been
discussed extensively and have focused on changes in sexual patterns, such as
increased oral sex or increasing numbers of sex partners,” the researchers
wrote. “A significant association has been shown between HPV-positive
tonsillar cancer and early initial sex or number of oral or vaginal sex
partners.”
The researchers said one study from the United States
also linked open-mouthed kissing with HPV infection and noted that these
findings could significantly affect the timing of prophylactic vaccination of
children.
“We suggest that we are encountering a slow
epidemic of mainly sexually transmitted HPV-induced [oropharyngeal squamous
cell carcinoma],” they wrote.
Studies examining factors in treating HPV-positive
cancers are conflicting, and the researchers said additional information is
needed. “Future prospective clinical studies, including diagnostics of
HPV, molecular and immunologic profiles, history of smoking, cessation of
smoking during therapy, and effects of different treatment modalities and their
side effects on quality of life, will be of benefit for personalized
treatment,” they said.
Further monitoring of vaccination’s effect on
HPV-positive cancers is also important, the researchers concluded.