Researchers at the Johns
Hopkins Kimmel Cancer Center have teased out two
distinct sets of
risk factors for head and neck cancers, suggesting that
there are two completely different kinds of
the disease.
In the study, head and neck tumors caused by the human
papillomavirus, a common sexually
transmitted virus, were most often linked to certain sexual
behaviors and marijuana use, rather than
to tobacco and alcohol. The Johns Hopkins scientists also
found that people with the viral-linked
cancer were younger, more likely to be white, married,
college-educated and have an annual income of
$50,000 or higher. By contrast, those not caused by HPV
were associated with tobacco smoking,
alcohol use and poor oral hygiene, which are the behaviors
most often linked to head and neck cancer.
"Our results indicate that HPV-positive and
HPV-negative head and neck cancers have different
risk-factor profiles and should be considered two distinct
diseases," said Maura L. Gillison, an
associate professor of oncology and
epidemiology at Johns Hopkins. "They just happen to
occur in the
same place."
The findings are published in the March 12 issue of
the Journal of the National Cancer
Institute.
Gillison and her colleagues first reported in 2000
that HPV infection is associated with the
development of some head and neck cancers, particularly in
the upper throat and back of the tongue,
where it has been observed in up to 72 percent of patients.
In related work, Gillison and colleagues
recently reported that HPV-linked cancer has nearly doubled
in incidence over the past 30 years in
the United States.
They also found that head and neck cancer patients
with HPV-positive tumors tend to survive
longer and are more responsive to treatment, compared with
patients with HPV-negative tumors. That
research was published online Feb. 12, also by the Journal
of the National Cancer Institute.
According to Gillison, the American Joint Committee on
Cancer is now considering incorporating
HPV status in its guidelines for determining clinical
stages of head and neck cancer.
For the current study, Gillison and her team studied
240 patients diagnosed with head and neck
squamous cell carcinomas at The Johns Hopkins Hospital
between 2000 and 2006 and determined
whether their tumors were positive or negative for HPV.
They formed a control group by matching up
to two people without cancer to each patient by similar age
and sex. All study participants completed a
computerized interview that asked questions about their
risk factors.
Overall, the researchers detected HPV16 in 92 cancer
patients. They found that HPV-positive
cancers were associated with several measures of sexual
behavior and exposure to marijuana but not
with tobacco or alcohol use, or with poor oral hygiene.
These associations became stronger with
increasing numbers of oral sex partners and with longer or
more intense use of marijuana. In fact,
among nonsmokers of tobacco, participants who smoked
marijuana for at least five years were 11 times
more likely to develop HPV-positive cancers.
Gillison says that her study is one of the first to
connect marijuana use with the development
of HPV-linked head and neck cancers. "It's possible that
other behaviors linked with marijuana use
could be the real culprit, and our results will need to be
confirmed," she said. Some reports show that
chemicals in marijuana called cannabinoids could affect the
immune system's ability to clear a viral
infection, Gillison said.
Sexual behaviors associated with HPV-positive cancers
included increasing numbers of lifetime
vaginal or oral sex partners, participating in casual sex
at least once, infrequent use of barriers during
vaginal or oral sex and having had at least one sexually
transmitted disease. HPV-negative cancers
were found to be associated with tobacco or alcohol use and
with poor oral hygiene but not with any
measure of sexual behavior or marijuana use. Poor oral
hygiene and tobacco and alcohol use are well-
known risk factors for non-HPV-related head and neck
cancers. Those who had heavily used tobacco
and alcohol were nearly five times more likely to develop
HPV-negative head and neck cancers.
Participants who brushed their teeth less than once a day
were four times more likely to develop HPV-
negative tumors.
Head and neck cancers occur in more than 35,000
Americans each year, and the Johns Hopkins
investigators believe that the rise in the HPV variety
could be due to changing sexual behaviors.
This research was supported by the Damon Runyon Cancer
Research Foundation, State of
Maryland Cigarette Restitution Fund and National Institute
of Dental and Craniofacial Research.
Co-authors were Gypsyamber D'Souza, William Westra,
Elizabeth Sugar, Weihong Xiao, Shahnaz
Begum and Raphael Viscidi.
GO TO